Measuring Hub Runout

Measuring Hub Runout

Excessive installed runout on hub-less rotors can be a problem. Because of this, we’ve prepared this article in order to help you diagnose and fix the issue. By following this guide, you can rest easy knowing that the job was completed efficiently and accurately. 

Solving Hub Runout

To determine if the hub is the cause of excessive runout, measure the hub runout. To do this, perform runout measurement and an indexing procedure as described here. If indexing determines that the hub is the cause of runout, hub runout should then be measured. The hub’s design will determine how the measurement should be performed. Figures 30.1 and 30.2 show two different hub flanges. First, figure 30.1 has a flat surface area outside the wheel studs while the hub in figure 30.2 has little to no flat surface outside the wheel studs. For your example, use the procedures below to measure hub runout.

Rotor illustration
Rotor illustration 2

Shouldered Hub

1. Setup the dial indicator as shown in the image below.

2. Position indicator plunger at a slight angle near the outside edge of the hub flange. Additionally, make sure that the dial indicator will not contact the wheel studs.

3. Next, using the appropriate size socket, rotate the hub in the direction that the dial indicator plunger is pointing. (in figure 30.3 the correct direction would be clockwise)

4. Note the difference between the lowest number and highest number obtained. This is the amount of hub runout. Most manufacturers do not provide a specification for hub runout. Generally speaking hub runout should be .001″ or less. Remember that the rotor runout caused by hub runout will be multiplied by the rotor’s larger diameter.

Dial indicator illustration

Non Shouldered Hub

1. Begin by setting up the dial indicator as shown in the image below.

2. Position the indicator plunger so that it is perpendicular to the hub’s mounting surface, evenly spaced between 2 wheel studs so that it contacts within a 1/4″ of the outside diameter of the hub flange as shown in figure 30.4

 

Dial indicator 2 illustration

3. Next, position the dial indicator scale so that the needle is aligned with the “0”. Gently pull the indicator plunger 1/4″ away from the flange surface, then bring it back to rest on the flange surface. The needle should return to “0”. If the needle is at “0” proceed to step 4. On the other hand, if the needle is not on “0” then repeat steps 1-2 making sure the vise grips are tight, the flexible mount is rigid when the lever is turned, and the dial indicator clamp is snug.]

4. Pull the plunger out and rotate the hub so that the indicator plunger is located midway between the next 2 wheel studs. Now, gently bring the plunger back to the hub flange. Continue by noting the indicator reading.

Repeat

5. Repeat step 4 for the remaining wheel studs making sure to note the indicator reading until the hub has been rotated a full 360 degrees. Recheck the indicator reading at the starting point to make sure that the needle is at “0”. If the needle is not on “0” then start the process over. This will be caused by the indicator mounting having shifted.

6. Note the difference between the lowest and highest number obtained. This is the amount of hub runout. Most manufacturers don’t provide a specification for this. Generally, the runout should be .001″ or less. Remember that the rotor runout caused by hub runout will be multiplied by the rotor’s larger diameter.

tip

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Rotor Indexing

Rotor Indexing

When you run into runout problems, there can be a few different culprits. Because of this, it is important to determine the correct source in order to fix the issue. One of the best ways to do this, is by rotor indexing. By performing an index not only will you find the problem, but often times, you’ll fix it as well. Typically, installed runout can be caused by any combination of the following:

 

  • Rotor has runout
  • Hub has runout
  • Hub to motor mating surface is not clean
This article will go over a process known as “indexing” in order to help you identify and correct any installed runout you may come across.

Rotor to Hub Index

The following steps will go over the indexing process. Following these steps will help you find the issue and, in most cases, fix it as well. To get started, follow the steps below to index the rotor to the hub.

Tip: Using this procedure will either correct the runout problem or tell you whether the problem is related to the hub or rotor

1. Measure rotor runout

2. If runout is greater than the allowable specification (usually no more than .002″) then proceed to the next step.

3. Index the rotor to a wheel stud.

4. Rotate rotor until the dial indicator reading is at its highest value. Use a magic marker to mark this point on the rotor and hub flange as shown in the image below:

Rust buildup

5. Next, remove the rotor. Check the hub and rotor mating surface for dislodged rust or anything else that could cause the runout. If the mating surface is good install the rotor by rotating it 2 lug positions from its original position.

6. Finally, Measure the runout. If it is now within the specifications, proceed to the next wheel. If not, rotate the rotor until the dial indicator reading is at its highest value. Continue by checking the position of the marks on the rotor and hub in relation to the high spot. If the high spot aligns with the rotor, the rotor is the source of the runout. If the high spot aligns with the mark on the hub, then the hub has runout.

Indicator Dial

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Rust and Runout

Rust and Runout

One possible cause for high speed pulsation is happens when rust builds up. This article will go over how rust causes this problem and the necessary steps to resolving the problem.

Cause

The problem occurs when one or more of the rotors installed have excessive runout. Generic specification being used by domestic OEMs is .002″. Excessive runout causes disc thickness variation (DTV) over time. The average for most vehicles is 3,000 to 6,000 miles. This number can vary up or down based on the variables involved.

Rust buildup in jacking

Rust on hub’s mating surface is a leading cause of runout. The rust can from to a point where it actually pushes the rotor away from the hub even with the wheel bolted on (See image above). This process has been termed “jacking”. It works much the same way as a tree root under a side walk. There are tremendous forces involved as the rust “grows” between the rotor and hub.

Solution

Cleaning of the rotor and hub’s mating surfaces is a critical part of the brake job. The hub to rotor mating surface must be free of rust or runout induced DTV can occur shortly after the brake job. As little as .001″ of rust at the outside edge of the hub will result in .002″ to .004″ of runout.

The method used to clean the hub depends on the severity of the rust buildup. The hub’s mating surface can be a difficult surface to clean due to the wheel studs. The area between the wheel stud and hub centering flange is the most difficult area to gain access to. Here are the best methods to clean the hub’s mating surface.

Method 1 - Mild Rust Build Up

1. Use an angle grinder equipped with a Scotch Brite disc to clean the majority of the surface area. Get as close to the studs as possible and change the disc when needed.

2. Finish the process by using the tool shown in the first image below to clean the area around the studs. This tool fits over the wheel stud to allow easy cleaning of the hard to reach area of the hub. The second image shown the finished result.

OTC Tool

Method 2 - Severe Rust Buildup

The hub shown in the first image below will not be able to be cleaned effectively using the steps outlined above. The end result would look something like the second image below. The OTC tool does NOT work on mild to heavy rust. It has a tendency to polish the rust instead of removing it. The most effective method is to use the following steps.

Rust Hub
Polished Rust

1. Abrasive blasting is the most effective method for rust removal. There is a specialized blast cabinet available that allows cleaning of the hub while it is still on the vehicle. The tool uses a drawstring boot to allow the unit to be used on the vehicle as shown in the image below.

Rust Buster

2. The following image show what the final product should look like. This is the same hub as shown above. This hub will not be the source of rust induced runout. While there are other methods that can be used to clean rusty hubs the method described above the most effective. Other methods can be time consuming, yield a lower quality job and may not result in all of the rust being removed.

Finished Product

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How to Verify Accuracy of Setup on Bench Lathe

How to Verify Accuracy of Setup on Bench Lathe

Bench lathe induced runout is one of the leading cause of runout induced DTV pulsation comebacks. Typically, there are three main reasons for bench lathe induced runout:

1. Arbor runout

2. Adapter condition

3. Not verifying accuracy of setup

This article will cover a process called “Scratch Cut” which is used to verify accuracy of setup.

Solution

All rotors and drums machined on a bench lathe should be scratch cut before machining. This is necessary to verify the accuracy of the lathe setup. Skipping this step can lead to machining runout into the rotor. The process of verifying the setup is commonly referred to as “scratch cut”. The list below shows each step of the process:

1. Position the bits away from the outside edge of the rotor.

2. Bring the outside bit in until it barely touches the rotor. While holding the outer knob, place the inner dial on zero. On lathes without this feature, take note of the dial reading.

3. Back the cutting tip away from the rotor a small distance and turn the lathe off.

4. Observe the scratch cut. If the scratch cut is at least 50% around the rotor proceed with the machining process. (first image) If the scratch cut is less than 50% then the setup needs to be verified. (second image)

Scratch on rotor more than 50 percent around
Rotor with a scratch less than 50 percent

Steps 5-10

5. Two things will cause a scratch cut less than 50%. The first is that the rotor has runout and needs to be machined.

6. The second is a problem in the setup. Adapter cleanliness, arbor runout and tightening of the arbor nut are the main causes of setup problems.

7. To verify the setup, loosen the arbor nut. While holding the inner and outer adapter rotate the rotor 180 degrees. Re-tighten the arbor nut. This process changes the relationship of the rotor and adapters.

8. Turn the lathe on and move the twin cutter in or out a small distance.

9. Make a second scratch cut by turning the dial to zero. On lathes without this feature, turn the dial into the same number as the first scratch cut. This process makes each scratch cut the same depth which makes comparing the cuts easier.

10. Back the cutting tip off a small distance and turn the lathe off. Compare the next two scratch cuts. If the problem is in the rotor, the cuts should be on top of one another. (See below)

11. A setup problem will cause the second cut to be in a different position from the first. (See first image below). If this is the case, disassemble everything and check for cleanliness, correct adapters and for nicks on the mating surface. (See second image below) Do not proceed with the machining process until the scratch cuts are in the same position. Doing so will include runout into the rotor.

Scratch Cut Not Matching
Clean Surfaces

Bonus Tip: EVERYTHING machined on a bench lathe should be scratch cut to verify accuracy. For additional info, see our article on bench lathe adapter service.

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Bench Lathe Adapter Service

Bench Lathe Adapter Service

When high speed pulsation occurs after 3,000-6,000 miles bench lathe induced runout is a likely culprit. This article will go over everything you need to do to fix this issue. Likewise, images are provided in order to help you visualize the steps necessary.

Bench Lathe Adapter Solution

Preventing the majority of bench lathe setup problems is a relatively easy process. For example, follow the following steps.

1. Arbor Shaft Runout

First, Measure the arbor runout and correct it if necessary. Typically, the specification for arbor runout near the end of the arbor is .002″. However, if the runout is outside of the specification, remove and clean the mating surfaces. If the problem persists, consult your bench lathe manual.

Arbor Shaft Runout

2. Arbor Face Runout

Second, measure the arbor face runout. Usually, the specification for this measurement is .0005″. If the measurement is off, a correction will have to be performed using the bench lathe manufacturer’s procedures.

Arbor Face Runout

3. Hubless Adapter Arbor Mating Surface

In some cases, you’ll come across adapters like the one pictured below. This adapter is typical in many shops. These kinds of adapters rly on the mating surface as well as the arbor face to be accurate and true. Because of the state of the one pictured, it would be impossible for an accurate setup with this adapter.

Dirty adapter face

4. Correcting Arbor Mating Surface

In order to fix a mating surface, it will have to be cleaned. To do so, place a piece of sandpaper on a flat surface and run the adapter’s small face up and down a few timers while applying even pressure. As a result, you’ll end up with something resembling the image below. Likewise, it is important not to worry about pits or indentations as these won’t effect the mating.

Clean Adapter Face

5. Indexing Adapter to Lathe:

(This step is optional if the arbor face runout was .0000″.) Next, if the arbor face runout was greater than zero, then the hubless adapters will have to be indexed to the lathe before continuing. This is important because some adapters have index marks cast into them while others don’t. As a result, if there is no index mark use a file to make an index mark on the edge of the small mating surface as shown in the image below.

Adapter Index Mark

6. Preparing Adapter for Machining

Next, install the adapter on the lathe and position the twin cutter to enable machining of the large mating surface as shown below. At times, it will be necessary to remove the opposite tool holder to achieve the proper clearance.

Twin cutter setup

7. Machining Large Mating Surface

Next, remove only as much material as is necessary to achieve a 360 degree cut. Typically, this only requires .002″ to .005″. Make a slow cut to machine the large mating surface. As a result, the mating surfaces becomes true to the lathe as shown below.

Finished product

8. Optional Adapters

Similarly, the same procedure can be used on the optional adapters available for most bench lathes such as the composite rotor adapter shown in the picture below.

Other adapters

Conclusion

The average bench lathe setup will take between 1 and 2 hours to preform. Once this procedure is performed it will become a simple matter of keeping the mating surfaces clean and free of nicks and burns. If the arbor face had runout and index marks were used then the adapter and arbor index marks should be aligned each time the adapters are used.

Even after this procedure has been completed, it is still necessary to check the setup. To do so, you’ll need to perform a scratch cut.

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Brake Lathe Arbor – Checking & Correcting Runout

Brake Lathe Arbor – Checking & Correcting Runout

If you’ve ever worked on brakes, you’ve likely used, or at least seen a brake lathe. This handy tool helps mechanics to machine rotors to the right specifications ensuring a smooth braking experience. However, there are times where the the brake lathe can end up causing more problems instead of solving them. This article will go over some of the issue that come up and how to prevent/solve them.

Causes of Brake Lathe Runout

Typically, there are three main reasons that brake lathe with cause runout:

1. Arbor runout

2. Adapter

3. Not verifying accuracy of setup

The good news? Each of these issues can be helped via the steps below.

Measuring Arbor Runout

Essentially, proper care mixed with periodic measurement will eliminate the arbor as a cause of brake lathe runout. For example, follow the steps below to check and correct arbor runout.

1.Witness Marks

Lathes using tapered arbors use witness marks to indicate the most accurate fit for the arbor to spindle. These marks are made at the factory after the arbor is matched to the lathe. For example, verify that the marks are aligned as shown in the image below.

Witness marks on a brake lathe

2. Position the Dial

Next, you’ll need to set up the dial indicator . For example, see the image below.

Dial indicator attached to brake lathe

3. Rotate and Measure

Finally, use the draw bar nut to rotate the spindle while also watching the dial. It is best to use a socket and ratchet when performing this step. Use a smooth 360 degree rotation for the most accurate measurement. If arbor runout is within specifications (typically nor more than .002 with the closer to zero the better.) No service is needed. If outside of specifications follow the steps below.

Correcting Excessive Arbor Runout

Once the issue has been found, steps should be take in order to correct it. The following section will go over the necessary steps to correcting the arbor runout.

1. Inspecting the Arbor(s)

Begin by removing the arbor. Inspect the arbor and spindle taper(s) for chips or rust build up. (See below) The tapered surfaces of the spindle should be cleaned using a fine to medium steel wool. The arbor’s tapered surface(s) can be cleaned using a wire wheel.

Rusted Taper

Note: Do NOT use sandpaper, emery cloth, or anything that could remove metal. The taper surfaces determine the arbor’s fit and changing them in any way could result in permanent damage to the accuracy of these surfaces.

2. Clean

Use a clean rag to wipe all mating surfaces before installing the arbor. Put a light coat of WD40 or similar treatment on the tapered surface(s) before installing. This will prevent rusting.

3.Witness Marks

Next, align the witness marks and tighten the arbor nut or draw bar to specification. Typically, it will be around 50-60ft lbs.

4. Repeat

Finally, repeat the steps found under “Measuring Arbor Runout”. If the measurement is now less than .002″ you are finished. Otherwise, follow the steps below to determine the cause.

Determining the Source

Even after completing all of the steps above, there are times that the specifications don’t match up. When this happens, it is important to figure out the cause, so that it can be fixed.

1. Greatest Runout

Rotate the arbor until the dial indicator is at its highest reading. This is the point of greatest runout. Use a magic marker to mark the point on the arbor as shown below. This mark will be used to determine if the arbor is the source of the excessive runout.

arbor high spot

2. Loosen

Next, loosen the arbor and rotate it 1/8 of a turn clockwise then tighten the drawbar. Continue by measuring the arbor runout.

3. If Less Than .002"

If runout is less than .002″, make a mark on the arbor at the spindle witness mark.

4. If More Than .002"

If the runout is more than .002″, loosen the drawbar and rotate the arbor 1/8th of a turn, then retighten th drawbar.

5. Re-Check

Now you are ready to re-check the runout.

6. Still Greater Than .002"

At this point, if the runout is still more than .002″ repeat steps 4 and 5 until the runout is less than .002″. Next mark the arbor to the spindle witness mark.

7. Check Mark

Finally, if the runout is still greater than .002″ after the arbor has been rotated 360 degrees, rotate the arbor until the maximum reading is shown. Next, check to see if the magic marker reference mark from step 1 is aligned with the dial indicator plunger. If the two are aligned, the arbor is bent and will have to be replaced.

Note: Some older lathes may not have a witness mark. Dial indicate the arbor and mark both the arbor and spindle.

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How to Diagnose Excessive Disc Thickness Variation (DTV)

How to Diagnose Excessive Disc Thickness Variation (DTV)

What is DTV?

When a rotors thickness varies at different locations, it is called disc thickness variation, or DTV for short. Typically, the average specification for DTV is .0005″. On the other hand, the maximum allowable variation in thickness on a rotor is 5 ten thousandths of an inch. Because this measurement is so small, it is not measurable at the shop level.

Disc Thickness Variation (DTV) Illustration
Image Credit: Bendix.com

Measuring the DTV

Most publications give instructions for measuring the DTV. Normally, the steps involve making 6-8 measurements at a specified distance from the edge of the rotor. Next, it’ll typically have a chart for you to compare the measurements with each other. In some cases, the measurements will show more than .0005″. Because of this, we know that the rotor has excessive DTV. Because the measurement is so small, it can only be observed in a laboratory environment.

Determining DTV

Since measuring the rotor in shop isn’t an option, it’s best to identify it via symptoms. For example, excessive DTV is the leading cause of high speed pulsation complaints. Likewise, DTV is typically more pronounced when stopping from speeds above 35mph. This is caused by the changing thickness of the rotor thus causing the caliper piston to move in and out. Similarly, the movement of the caliper piston causes fluid movement in the hydraulic system that is felt in the brake pedal.

Symptoms

When a vehicle is exhibiting high speed pulsation, then one or more of the rotors has excessive DTV. For instance, if the vehicle is disc/drum, then both front rotors should be serviced according to their thickness condition. In another example, if the vehicle is equipped with 4 wheel disc brakes, use the location of the vibration to help pinpoint whether it comes from the front or rear. Typically, if the steering wheel, dashboard, and/or brake pedal shake, the problem will be related to the front rotors. Otherwise, when the vibration comes from the seat of floorboard, it is likely to be a rear rotor issue. As a rule, DTV is more common on front disc brakes than rear.

Bonus Tip: You CANNOT measure thickness variation at the shop level. Because of this, you must rely on the symptom it produces to in order to know whether you have it or not.

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How to Measure Rotor Runout

How to Measure Rotor Runout

The rotor runout dial indicator is used primarily to measure rotor runout. Likewise, it may be used to measure arbor runout on the bench lathe, wheel bearing play, and hub runout. Even so, the tool must be used to correctly in order to get an accurate reading. Because of this, runout measurement is often not performed correctly and yields inaccurate results.As an example, this article will go over the correct steps to completing the process.

How to perform a Rotor Runout Measurement

1. Attach Vise Grips:

To begin, attach the flexible mount to vise grips. As you’ll see, there should be three mounting holes in the mounting block. Typically, the end one will be the best option, use it when possible.

Note: Make sure the flexible mount is screwed in tightly to the vise grip mount

In order to keep everything stable, be sure to locate a solid mounting point on the vehicle. For example, consider the caliper mounting bracket, pad rails, lower strut mounting bolt, or steering arm. On the other hand, be sure to mount on a stationary location that is not attached to the rotor.

Vice Grips Attached to Bolt

In addition, there must not be any bearing play on hub style rotors. If excessive play is present, adjust the bearing before you measure. On the other hand, hubless rotors have to be secured with spacers and lug nuts. For example, a 5 lug hub should use 3 lug nuts. Likewise, on a 4 lug hub, use 2 opposite lugs with spacers. Likewise, the lug nuts should be installed backwards (when possible) with the flat sides against the spacers.

2. Attach Dial Indicator

To attach the dial indicator, loosen the clamp screw and tighten it to a point that the indicator can move freely. Next, make sure that the red handle points directly in line with the base of the flexible mount. To do this, turn the adjusting screw clockwise. (see below)

Indicator Clamp

3. Set the Plunger

Next, locate the dial indicator plunger as shown below. The tip should be about 1/4″ from the edge of the rotor. In addition, the plunger should be placed on a smooth portion of the rotor. If necessary, take the rotor runout reading on the inner surface of the rotor. Likewise, the plunger should extend out of the housing and the contact tip should be at a slight angle in line with the edge of the rotor. (see below)

Close Up of Needle

4. Add Tension to the Rotor Runout

While holding the indication in position, rotate the red tension handle 189 degrees or until there is enough tension to hold the unit stationary.

Note: Make sure the tip of the indicator is screwed in all the way or else vibration will occur during the reading.

5. Take the Rotor Runout Reading

Finally, the rotor runout reading can be taken. To do this, rotate the rotor in the direction that the dial indicator tip is pointing. Next, watch the needle for the lowest and highest number reached during one revolution. The runout number will be the difference between these two numbers. For example, if the lowest reading was 65 and the highest was 69 the runout is .004″ (see below).

Runout reading on dial meter

To use the “zero” feature rotate the rotor until the lowest reading is obtained. Next, loosen the set screw and rotate the black dial until the needle point to zero. Finally, rotate the rotor a complete revolution and note the amount of runout. As a result, the needle will start and stop at zero without going below it.

Bonus Tip: It takes less than 60 seconds to measure rotor runout and KNOW whether the rotor runout will be an issue in a vehicle that comes back with pulsation.

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Reoccurring Pulsation

Reoccurring Pulsation

High speed pulsation occurring after a brake job is called reoccurring pulsation. This article will go over the most common causes and solutions. In addition, several tips and tricks are noted through out the article.

Reoccurring Pulsation Cause 1:

One or more of the rotors were installed with excessive runout. Generic specification being used by domestic OEMs is .002”. Excessive runout causes disc thickness variation (DTV) over time. The average for most vehicles is 3,000 to 6,000 miles. This number can vary up or down based on the variables involved.

Cause 2:

Insufficient clearance between inboard and outboard brake pads and rotor’s friction surface. The closer the brake pads are to the rotor’s friction surface the smaller the amount of runout needed to produce disc thickness variation (DTV).

Reoccurring Pulsation Solution 1:

Rotors must be installed with runout less than vehicle’s specifications in order to eliminate runout induced DTV. There are 2 options to perform this.

Option 1:

Use an on-the-car lathe to machine the rotors true to the hub. Make sure to index the rotor to the hub if removing it after the machining process. Make sure to properly torque the wheels using the method described in step 6 below.

NOTE: When performing on-the-car machining on vehicles equipped with ABS make sure none of the machining chips accumulate on the magnetic sensor tip. This could trigger false activation of the ABS or fault codes. See Figure 22.1

Lathe Chips

Option 2:

If using a bench lathe to perform off the vehicle machining follow these steps:

1. If resurfacing the rotor(s) use proper machining techniques and make sure the lathe is in good working condition. On hubless rotors make sure to clean the mating surfaces with an appropriate tool. Scratch cut all rotors to ensure accurate setup.

2. Clean the rotor before installing on vehicle to prevent machining dust from contaminating brake pads.

3. Before installing hubless rotors, clean the hub mating surface using an appropriate tool(s). Failure to properly clean this surface can prevent achieving the proper installed runout.

4. When installing new or machined hubless rotors the installed runout should be checked. Using spacers on the studs tighten all lugs to the proper torque using the correct sequence. Measure runout. If runout is not less than manufacturer’s specification index the rotor on the hub to achieve the lowest amount of lateral runout.

5. Before indexing mark the high spot on the rotor and hub using a magic marker or paint stick as shown in Figure 22.2. Indexing involves removing the rotor and rotating it one or two lugs and reinstalling. Repeat this until the installed runout is below specification. If runout is out of specifications and does not change as the rotor is rotated check to see if the high spot moves with the rotor or stays with the hub. This will identify the cause of the runout.

Indexing dial

6. Properly torque the wheel lugs using either a hand torque wrench or torque stick sockets. When torquing wheels use a step torque process. To step torque the lugs tighten all lugs to half the normal torque using proper sequence and then fully torque lugs using same process. Make sure your impact has been calibrated before using torque sticks.

Solution 2

Look closely at Figures 22.3 & 22.4. Both rotors shown have the same runout but what they don’t have is the same gap between the pads and rotor. The gap between the pads and rotors in Figure 22.3 is much smaller than that of Figure 22.4. The smaller the gap the more sensitive the vehicle will be to runout induced DTV. Remember the wear of the high and low spots occurs during both brake apply and release. If something in the caliper assembly is preventing a full or complete release of either the outboard or inboard pad that wheel will be more susceptible to this problem. Improper release of either pad could make even those rotors at or below .002” prone to this problem.

Small Pad to Rotor Gap
Large Pad to Rotor Gap

Pad Release

Effective inboard pad release will be effected by two types of conditions. The first of these involves how well the piston releases. A piston that does not return as far as it should reduces the gap between the inboard pad and rotor. Mileage, brake fluid condition, dust boot seal integrity all can impact the piston’s ability to release properly. The second condition that can effect the release of the inboard pad involves how easy the pad can move in relationship to the caliper mounting bracket, knuckle or slide rails. If the inboard pad binds then complete release will not take place.

Outboard pad release can be impacted by two categories of failures as well. The most common of these is the slide hardware. If the caliper housing is not free to move on its mounting hardware then outboard pad release will be effected. The other category is the same as for inboard pad release, that is anything causing the outboard pad to bind where it contacts the bracket, knuckle or slide rails.

No Short Cuts

Nothing new about what impacts inboard or outboard pad wear but understanding its influence on the issue of runout induced DTV is a fairly new concept. The moral of the story is short cutting quality brake work impacts more than just pad life. The old “pad slap” has more chances to come back and haunt you than what you might have considered. Remember just because the caliper applies and releases doesn’t guarantee its doing it as effectively as it should. Look at the big picture when doing your brake inspection. A few more minutes covering the details up front will pay big dividends in the long run. A saying I like to use sums it all up – “I would rather be paid today for what is wrong with the vehicle than have to give it away tomorrow”.

More Info: The fact that excessive runout is the leading cause of reoccurring pulsation should not be anything new. The principal is easy, too much runout on fixed bearing vehicles causes the high and low spot of the rotor to scrape against the pads. This scraping occurs during both non-braking and braking. Over time the high and low spots are worn thinner than the other portions of the rotor. This difference in thickness is known as disc thickness variation or DTV (See Figure 22.5). It is also called parallelism. The two friction surfaces of a rotor are supposed to be parallel to one another to within a certain tolerance. The average value for this specification is .0005”. As little as 5 ten thousands of an inch or another way to say it would be ó of one thousandth of an inch tolerance is all that is allowed.

Disc Thickness Variation DTV Views

DTV

If DTV is in excess of acceptable limits the thin spots pass between the pads during brake apply causing the caliper piston must move out to take up the gap. The thick portions of the rotor push the piston back. The in and out movement of the piston causes the pedal to pulsate especially at speeds above 35mph. What has been stressed is the importance of getting the rotor’s installed runout to acceptable levels. Most domestic OEMs are agreeing that this amount is .002” or less. While this is definitely the most important aspect of curing the reoccurring pulsation it is not the only thing to consider. There are other factors that will contribute to the vehicle’s sensitivity to this.

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Rotor & Drum Specification Accuracy

Rotor & Drum Specification Accuracy

Unfortunately, not all specifications are reliable. As a result, it can sometimes be tricky to get a quality job done. Because consolidated specification sources often make mistakes, it is important to make sure you find the right numbers. This article aims to help you learn how to verify rotor and drum specifications in order to complete a job. In particular, the example below will help illustrate a potential problem, and how to fix it.

The Specification Solution:

Take a close look the following chart, you’ll notice that the 1998 Skylark has different “machine to” specifications. As you can see, points “A” “B” and “C” are all different. Because of the differences, issues can occur. For instance, using the wrong specifications could result in the machining of a rotor that should have been replaced, instead of serviced.

Rotor Specification Chart

As a mechanic, you are making some pretty important decisions. When it comes to rotors and drums, you need to ensure that your numbers are accurate. For example, try to find two specifications from different sources. For the most accurate information, look to the rotor itself, information providers, and parts manufacturers.

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Rotor & Drum Specification Issues

Rotor & Drum Specification Issues

Machining rotors and drums can be a relatively straightforward task. You look up specifications and follow what they say, right? What about when there are not specifications listed? To help you out, this article will show you what to do when you can’t find the numbers you need to get the job done. Likewise, there will be various tips as you read. 

Solution:

No Machine to Specification Listed

Many vehicles no longer provide a machine to specification. However, this does not mean the rotor is not serviceable. In fact, most of these rotors are allowed to be machined to the discard specification. Though possible, it is not a practical procedure in a shop environment. This is especially true in the states where there are safety inspections performed. For instance, it is possible to perform a brake job and have the vehicle fail a state inspection only a couple of months later.

The chart below shows an example of this. In the image no machine to specification is given. Instead “NS“ is listed. The “NS” is short for “Not supplied by manufacturer”.

Table showing various machine to specifications

In this case, the machine to is calculated by adding .015” to the discard specification provided. In the case adding .015” to this would yield a machine to thickness of .995”.

No Discard Specification Provided

In the chart below, no discard specification is given. Instead a footnote number is listed. In particular, the footnote listed is number 2 which can be found at the end of the make section. Footnote 2 says:

“Discard when thickness is smaller than the minimum machining specification”

Brake specifications guide

As a result, the discard and machine to specification are the same number. This would not be practical for the customer. For example, if the rotor were machined down it would go beyond service in a very short period of time. Consequently, another brake inspection would result in the rotor being under specifications. Because of this the industry has adopted creating a revised machine to specification by adding .015” to the number provided. In the case of the 2001-99 Cougar the machine to listed is .874”. So, adding .015” to it will bring the revised machine to up to .889”. This is number you would use to determine whether the rotor can be machined or not. The .015” allows for normal rotor wear during the life of the friction material.

NOTE: Although it is best to use the aftermarket approach, it is acceptable to machine these rotors down to the machine to specification listed. The invoice should be marked “rotors at minimum machining/discard” to avoid future problems.

Brake Drum

The same holds true for brake drums. There is no drum discard specification provided for the vehicles in the highlighted box. Instead, a footnote number 3 is listed and that footnote says:

“Discard when diameter is greater than the maximum machining specification”

This means the maximum machining diameter and discard diameter are the same for these vehicles. If the drum were machined up to the machine to it would go beyond service in a very short period of time. Another brake inspection or a state inspection would result in the drum being over specifications after just being serviced. The industry has adopted the position of creating a revised machine to specification by subtracting .015” from the number provided. In the case of the 2001-99 Cougar the machine to listed is 9.040”. Subtracting .015” from this value would result in a machine to specification of 9.025”. This is the number you would use to determine whether to machine the drum or not.

Bonus Tip:  ‘NS” does NOT mean “Not Serviceable” as some technicians have been led to believe. It means “Not Supplied”.

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How To Determine if A Rotor Can Be Serviced

How To Determine if A Rotor Can Be Serviced

The determining factors in whether or not a rotor can be serviced are both dimensions and condition. Because of this it’s important to know when to service or replace the rotor in order to avoid incorrect information that leads to over or under selling.The dimensions determine whether it can be machined, replaced or in some cases left alone. Not understanding the meaning of the dimensions involved in making these decisions can lead to a rotor being machined when it shouldn’t be. Likewise, its possible a new rotor sells when the old rotor was still serviceable.

Rotor Solution

Understanding all of the critical dimensions of a rotor will allow accurate determination of the part condition and the type of recommendation that should be made. In the rest of this article, you will learn all of the important dimensions necessary.

Nominal Thickness:

Nominal thickness is the thickness of a new rotor. While this thickness is not normally used, it is listed in most specification books.

Machine to Thickness:

This is the thinnest point that a rotor can be machined to and still be put back into service. The “machine to thickness” is there to provide enough rotor material to last the life of one set of pads. Essentially, the idea is to make sure that the pad will wear through before the rotor does. To help you visualize, the average difference between nominal and machine to thickness is .050“ to .060“. The typical difference between machine to and discard (explained below) is .015“. See the image below:

Rotor Dimensions

One common myth, called throw away motors, says that late model vehicles have no meat on them and are thus not meant to be machined. This is not true. Again, the average rotor provides .050“ to .060“ with some giving as much as .100“ between nominal and machine to thickness. With the average machining taking off .010“ to .015“ there is usually room for at least on machining. The only true throwaways are marked like the one in Images below. The footnote (3) on this BMW denotes the rotor should be replaced not machined. True throwaway rotors are marked in this fashion.

Throwaway Rotor Footnote
Throw away rotor footnote

Rotor Discard Thickness

The thickness at which a rotor should be replaced is called the discard thickness. One common understanding is that the discard thickness is a heat related dimension. For example, if a rotor is at or below discard thickness it cannot dissipate the heat generated, however, this is not correct. Discard thickness is the thinnest a rotor can wear to. If the brake pads wear to nothing the caliper piston won‘t fall out of the caliper housing. It has nothing to do with heat. See the image below.

Discard thickness diagram

Many vehicles with a rotor at or below discard stop without any issues. The only sure way to know that a part is below discard is to measure the it and compare the measurement to the specifications.

Parallesism (Disc Thickness Variation, DTV)

The two friction surfaces of a rotor are designed to be parallel to one another within a certain specification. The allowable tolerance is known as parallelism. It is also known as the rotor‘s disc thickness variation or DTV. See Below.

DTV view diagram

Other Rotor Factors

A common question presented about rotors involves the thickness of one friction disc to the other on vented rotors as shown in the image below. There is not a published specification for the allowable tolerance for the difference in the thickness of one disc to the other. Some rotors are actually designed intentionally with different thickness discs. It is generally accepted that small differences are acceptable and are either intentional or a result of manufacturing variations.

Friction Discs

When machining, the thickness of one friction disc to the other should be taken into consideration. For example, if a rotor is gouged on one friction surface due to metal to metal contact with the brake pad but not the other, it could be possible to machine the gouge out and the rotor still be over machine to thickness. The problem would be that the gouged friction disc would be considerably thinner than the opposite disc. When faced with this situation common sense is the only guide. If the gouge is deep enough to result in having to remove a considerable amount of material it is probably best to replace the rotor.

Corrosion and rust can also have an impact on the rotor‘s ability to function correctly. The first image below shows clogged vent holes due to rust buildup. This part is thick enough to machine but the rust will prevent proper cooling. Likewise, the second image below has experience enough corrosion to actually weaken its structural integrity.

Plugged Fins

The rust has eaten away at the thickness of the cooling fins. This condition could result in the two halves of the part separating resulting in a catastrophic brake failure. Always perform a thorough visual inspection of the rotor to determine its condition and serviceability.

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What To Do About Brake Noise

What To Do About Brake Noise

Both customers and technicians hate dealing with brake noise. As you can imagine, customers find brake noise annoying and embarrassing. On the other hand,Technicians find brake noise frustrating and unproductive. Unfortunately, both groups find brake noise all too common. Most shops that perform brake service will tell you that brake noise represents the most common reason for brake comebacks.

Brake noise is the layman’s description of the symptom. In fact, brake noise is actually vibration that is occurring at a frequency that is audible to the human ear. All brakes make noise or vibrate. The difference is that most brakes operate at a frequency that we can’t hear.

The Solution to Brake Noise

To prevent or fix brake noise all you have to do is make sure the brakes operate (or vibrate) at the right frequency. In theory it really is that simple, but in real life there is often much more to it than meets the eye. There are many variables involved in the equation that can result in brake noise. Understanding these variables is the starting point of preventing brake noise complaints. Notice the word “prevent” not fix. This should be our primary goal. By getting a handle on how to prevent noise complaints from occurring, you will be better able to handle any comebacks.

Because most brake noise complaints involve disc brakes, we are going to focus our attention on them. As the brake pedal is applied and the pads are squeezed against the rotor, vibration is produced. For example, the points where the vibration takes place are pictured in the image below. Vibration can occur between the:

1. Pads and rotor

2. Pads and Caliper

3. Caliper and knuckle or mounting bracket

4. Knuckle and pads or mounting bracket

5. Caliper and mounting hardware

Diagram of brakes

The number of points where the vibration occurs will vary with the type of disc brake used. Likewise, the type of brake will also determine which causes will be more common. As you can see from the list, the prevention of most brake noise complaints will boil down to two things: performing quality brake service and using quality parts. Through the rest of this article you will learn about each potential problem spot, and how to prevent noise coming from each of them.

Potential Brake Noise Problem Spots

Rotor Finish

The rotors smoothness on its friction surface is important in preventing brake noise complaints. This is especially true right after a brake job is performed. The smoother the surface at the start of a brake job the lower than chances for brake noise.

Friction Material

Many people think that the brake pad is the leading culprit in creating brake noise. While that can be the case, it isn’t always true. If you have access to Mitchell On Demand or All Data you might want to take some time and look through some of the TSB’s (Technical Service Bulletins) dealing with brake noise. Many of these bulletins will tell you that a change in material solves the problem.

If you take a closer look, you would see that it is not the only method used. How does this relate to you and the friction material you are using? If you use a quality product from a reputable supplier then you should not have noise problems with MOST vehicles. Quality pads should be designed after the OEM pad. This means they should have shims, tapered edges or dust slots if the OEM pads were equipped with these features.

Pad Shims

Pad shims are used as an insulator between the pads and caliper. This serves to change the frequency of the vibration so brake noise is eliminated. The shims could be attached to the brake pad or they could be supplied as separate parts. Make sure your replacement pads are shimmed to match the OE pads and when servicing vehicles with separate shims either reuse the shims if in good condition or replace them. Do not reuse shims where the protective coating has worn off or if the shims are rusting and flaking. Do yourself a favor and add the cost of replacing the shims into your estimate now instead of giving them away later.

Pad Hardwear

Brake drum

It used to be that imports were the only vehicles using pad anti-rattle hardware but now disc brake assemblies similar to that shown in the image above have become the standard on many domestic vehicles. The pads “snap” into the caliper mounting bracket and are held in place by various clips. The caliper straddles the assembly and serves only to provide the squeezing of the pads against the rotor. 

The caliper mounting bracket absorbs all of the braking force and maintains the pad’s position. The anti-rattle hardware applies tension to the pads so they fit snugly against the mounting bracket. These clips are essentially small springs made of stainless steel. They are subjected to the same heating and cooling as rear brake hardware. How many of you are strong believers that the brake shoe hardware should be changed with each set of shoes? What’s the difference with the front hardware? Simply cleaning and reinstalling it won’t be good enough in many cases. 

Some add an extra step of “re-tensioning” the clips by bending the tabs slightly. This may work for a short time but won’t provide a long-term solution. Suggesting the replacement of this hardware with each pad replacement is something you should consider. The hardware can be pricey and you should explain to the customer why you are suggesting it. If they decline and have a noise problem later then you are in a better position than if you said nothing about the hardware.

Caliper Hardware

Rubber bussing worn down

Most vehicles use floating calipers. The rubber bushings or sleeves in these calipers allow the caliper to move freely on brake apply and release. They wear over time and can increase the chances for brake noise. Careful inspection should be done and replacement should be suggested or required based on the findings. If the bushings or sleeves are too loose fitting the caliper will be allowed to move too much (See Image Above). This will increase the chances for a brake noise problem especially if other problems are present. Again, if the customer declines the service, mark the invoice accordingly. If a noise comeback occurs, you will have set the groundwork for what needs to be done. It’s a better position to be in then having nothing to fall back on.

Cleaning & Lubricating

Cleaning & lubing – The amount and type of cleaning you will have to do will vary with the type of vehicle being serviced and the area of the country you live in. Some vehicles have only a few key areas that need to be cleaned when servicing the disc brakes while others require considerable more effort. If you work in the south or out west then you won’t have to deal with too much rust like those of us in the snow belt. For more information on cleaning and lubing see our blog post.

Pad Staking

Caliper off
Stake On Caliper

Some outboard pads are designed to be “staked” to the caliper. This staking holds the pad firmly in place and prevents vibration. Older domestic RWD vehicles use outboard pads that stake to the caliper using small tabs as shown in the first image above. This style of pad is best staked off of the caliper. Bend the tabs on the pad until a press fit is needed to install it. Use a pair or channel locks to press it onto the caliper using a piece of cardboard to protect the friction material. 

Some General Motors vehicles require a different procedure to stake the outboard pad. The second pads pictured are first installed on the vehicle. Next a chisel is driven between the hat of the rotor and the base of the pad to hold the pad against the caliper. Now, have an assistant apply and hold the brake pedal. This will hold the pads in place while you perform the staking. The tabs should be bent over at about a 45-degree angle. Release the brakes and check the tightness. No movement should be felt between the pad and caliper.

Pad Break In

Starting the mating of the pads to the rotor and getting the brake job off on the right foot is critical to the long term success of the brakes. See our blog post for more information on the proper break-in procedures.

Final Thoughts

If you apply the information above and the information contained in the related articles mentioned, you will eliminate 8 of 10 brake noise comebacks. If that is the case what do you do with the other 2? This is when you consider the friction material as the possible culprit. If involved in a brake noise comeback, first look at whether any of the steps above have been skipped or not performed properly, in other words, check to see if a quality brake job was performed. If the answer is yes, then consider an alternate pad.

Brake pad noise is one of those things that annoys everybody so it is better to do the best job possible to prevent it.

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What is “Friction Break In” and How To Do It

What is “Friction Break In” and How To Do It

When completing a brake job, it can be tempting to replace parts and call it done. However, to really complete the job, it is important to complete a friction break in. Essentially, this process helps get the brakes ready for every day use. To help you out, this article will go over why and how to complete a friction brake in.

How to Perform a Friction Break In

Once a job has been completed, a test drive should be performed. In order to do this, the test drive has two goals. The first is to make sure the brake system is operating properly. To do this, a test drive is performed in order to help in the mating of the pads to the rotors. This is often called a “break in” or “burnishing”. In any case, no matter what you choose to call it, it is important to get it done. Depending on who you ask, the number of stops you should make with new brakes will vary. Typically however, A good average is 10 to 12. To mate the pads effectively, make 10 to 12 stops from about 30 mph down to 10 mph. Equally as important, allow about 30 seconds between stops for cooling.

Delivering to the Customer

Next up, the second thing you should do is educate the customer. When you deliver the vehicle to the customer, advise them not to do any severe braking for the first couple of hundred miles. Likewise, let them know to stay away from towing or hauling, while also trying to anticipate their stops when possible.

Often times, there are two types of customers you’ll want to watch out for, and educate.The first group of customers think they need to slam the brakes several times directly after the brake job. As a result, many customers make hard stops right after the job is done, causing potentially irreversible effects on the performance of the brake job. On the other hand, the second group of customers are those that will leave your shop and go on vacation. Because of this, they end up towing a lot of weight and putting a lot of stress on the brakes. Not catching that customer can cost you big time. That is why you should talk to and educate your customers, it will benefit both of you in the long run.

OEMs & Friction Break In

To further prove the point, some OEMs endorse the same steps on their new cars. For example, the image below shows the new vehicle break-in page from an owners manual on a late model GM vehicle. Just like above, you can see similar steps.

New vehicle break-in manual instructions

While both parts can be helpful, there are times it will not be practical to perform the second part of the brake-in process. For example, Asking fleet customers to not tow or haul for 200 miles is not practical. In these cases, try and at least double the number of stops taken in the first step to bring the process closer to completion. Remember that proper friction break in is par of any quality brake job.

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Slide Rail Repair

Slide Rail Repair

This article will go over the cause and solution for slide rail repair.

Slide Rail Repair - Cause

Worn down slide rail

The slide rails wear down due to the tremendous forces during braking and lack of lubrication. The constant force of the brake pads being pushed into the slide rails combined with the constant back and forth movement causes “dimples” to wear in the most used areas.

Slide Rail Repair - Solution

In theory, the only fix to this problem is to replace the part with the worn slide rails. Depending on the application this will either be the caliper mounting bracket or the entire steering knuckle. Neither of these repairs is practical.

The slide rails can be repaired following the steps below:

1. Clean the slide rail surfaces down to bare metal taking care not to remove good material. (see below)

Cleaned Slide Rail

2. Using a MIG welder fill the worn spots making sure to use the necessary settings to get good penetration. Try to avoid building the area up too high. The more buildup the more work.

Welded Slide Rail

3. Using an angle grinder with an abrasive sanding disc rough in the repaired area. Use the surrounding surfaces as a reference.

4. When close, use a Scotch-Brite disc to perform the finish work. The area can be checked using a straight edge.

Completed Side Rail

5. Check the final repair by sliding the pad the full length of the slide rails while checking for binding.

Bonus Tip:

Using this process will save your customer money, provide a legitimate profit for the shop, and restore the knuckle to like new condition.

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How To Fix Binding Calipers on Ford Light Trucks

How To Fix Binding Calipers on Ford Light Trucks

When calipers bind, it causes premature outboard pad wear. This article will go over how this issue is caused, and how to fix it. (specifically for binding calipers on ford light trucks. We’ve done our best to provide the help you’ll need, but if you still have answers after reading, check out the buttons at the bottom of the page. We have some great resources for you to check out.

Understand the Cause of Binding Calipers on Ford

When you experience binding calipers on ford light trucks, there are two main possible causes:

1. Using petroleum based lubricants on this caliper design can cause the rubber in the keepers to swell. Swelling of the rubber will cause the caliper to bind on release.

2. Buildup of rust and corrosion between the caliper/keeper/knuckle or failure to properly clean the mating surfaces of the caliper/keeper/knuckle.

The Solution

To fix the problem, simply pair the cause above with the solution below:

1. Ford states in TSB 95-5A-13 to use only a high quality silicone lubricant when servicing these trucks. Silicone will not effect the rubber and serves to repel any water that might get into it.

2. Whenever servicing the brake pads on this type of caliper, make sure to clean all mating surfaces before applying the lubricant.

More Important Information

Many Ford light trucks and SUVs use the sliding caliper pictured below. When performing service on this type of caliper it is important to use the correct type of lubricant.

Ford service information states to use only a high quality silicone lube. Use of any petroleum based lubricant will cause the rubber core to swell. As a result, the swelling will restrict the caliper movement and result in outboard pad wear. Moly-lube, anti-seize, white lithium grease and most other commonly used lubricants are petroleum based and should never be used on rubber parts. Use of the silicone lube will not only prevent damage to the rubber core of the keeper but silicone also repels water.

Brake Calipers

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How to Clean and Lubricate Brake Parts

How to Clean and Lubricate Brake Parts

Nobody likes it when their customers come back with complaints. That is why it is important that we do everything we can to prevent it. When it comes to brake jobs one really effective way to do this is to clean and lubricate brake parts. This article will go over the best method of achieving just that. 

Clean and Lubricate Brake Parts

Because each vehicle is different, the amount and type of cleaning you will have to do can vary. Depending on the type of vehicle, and the are of the country you are in, you may have to take different steps to effectively clean the brake parts. Some vehicles have only a few key areas that need to be cleaned while others require considerable more effort. For example, if you work in the south or out west, then you are unlikely to run into too many rust problems. On the other hand, those in the snow belt are almost always going to find rusty car parts. For the purpose of this article, we will show you how to clean and lubricate a rusted part, like the one below:

Rusted mounting brackets

Aggressive Cleaning

It is important to clean parts that look like this, if you don’t you’re likely to see problems down the road. When cleaning make sure to only remove the corrosion and not the good metal. In the image below, the bracket had a number of surfaces damaged by an aggressive cleaning with an angle grinder. This can cause the pads to fit too loosely or cause other related problems.

Mounting bracket that has been over cleaned

Cleaning Caliper "Ears"

One area that is commonly missed is the caliper “ears” that support the outer pad. These flat surfaces can have considerable rust buildup over time as shown below. Likewise, some brake quiet products can cause a similar buildup. If there are remnants of these products on the caliper’s mating surface, it will reduce the surface contact and could increase the chances for brake noise. Failure to clean these surfaces will not allow the outboard pad to sit square against the caliper, thus increasing the chances for vibration.

Caliper "ears" that are corroded

Lubricating the Brake Parts

After all of the surfaces have been cleaned, they need to be lubricated. There are many choices out there for brake lube and even more opinions on which ones to use. We recommend the use of a high quality moly-lube on all metal to metal surfaces or high quality silicone lube for metal to rubber parts. Silicone is best for metal to rubber because silicone repels moisture and creates a nice barrier when used properly. 

When it comes to lubricants like these remember that “a little goes a long way”. Too much can actually cause issues. For example, the bracket in the image below should have a light film of moly-lube applied as shown in figure 1. Next, install the anti-rattle hardware and apply a thin film to the surfaces that contact the brake pads as shown in the following image (figure 2). The bracket can now be installed on the vehicle.

Lubricated mounting bracket
Figure 1
Lubed mounting clips
Figure 2

Cleaning and Lubricating Brake Pads

Ok, so you’ve figured out the mounting bracket, but what about the brake pads? Again, most experts agree that a thin film of moly-lube is the best method to combat brake noise. They key here is to apply it where it will make the biggest difference. Rather than applying it to the entire back of each pad, apply a thin layer to each caliper “ear” and add a small circle on the inboard pad as shown in figure 3. The same should be done for pads with shims. On vehicles with multilayered shims, put a thin layer between each layer. In fact, this is how most vehicles come from the factory.

Brake pad and ears lubricated with a thin film of moly-lube

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Outboard Pad Wear and/or Brake Pull

Outboard Pad Wear and/or Brake Pull

If you’ve read any of our other articles, you’ll know that we’ve got a mechanical tip for just about all things brake. This article is no different. We’ll be going over one common cause for outboard pad wear and/or brake pull.

On Chevy and GM trucks it can be common to experience brake pull, and/or outboard premature pad wear. This article will go over the problem, cause, and solution for anyone that might have come across this problem. As suggested above this article will be applicable to anyone working on Chevy and GM trucks. We’ve tried our best to help you be able to fix the problem, but if you find yourself needing more help, check out the buttons at the bottom of the page.

Brake Pull From Steering Knuckle

This problem is caused by having insufficient clearance between the caliper and steering knuckle (see below). Heat expansion causes the caliper to bind in the knuckle, causing side to side brake imbalance. This condition will also prevent proper outboard pad release and will result in premature outboard pad wear as well.

Caliper Clearance

Solution:

If one of these trucks presents itself with the symptom of brake lead or pull and/or premature outboard pad wear the caliper to knuckle clearance should be checked. Follow the steps below:

1. Measure the clearance individually and add the two values together. Total clearance should be greater than .010″. If clearances are not within the tolerances go to the next step.

2. Correct clearances by filing metal off of the knuckle stops in order to achieve a total clearance between .010″ and .024″ (See image below).

Checking GM Caliper Clearance

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Stoplight Switch Adjustment & Pad Wear

Stoplight Switch Adjustment & Pad Wear

While there are many causes of premature pad wear (see our previous articles here), stoplight switch adjustment can be a common one. In fact, it is common enough to have been included in various TSB’s over the years. This article will go into how to deal with this problem specifically.

Potential Spotlight Switch Problems

Incorrect stoplight switch adjustment can prevent the brake pedal from returning to a point that allows the cup seals in the master cylinder to open the vent ports as shown in the image below.

Vent Port diagram

The Vent ports allow for fluid expansion when the brakes get hot. If they are not open a residual pressure will be created due to the expanding fluid. The residual pressure will cause the calipers to apply the brake pads slightly and will result in premature pad wear.

Adjustable Stoplight Switche

Vehicles with adjustable stoplight switches will use one of two varieties, adjustable body type or self-ratcheting plunger type. Each is covered below:

Adjustable Body Type Stoplight Switch

  1. Verify complaint – if there is drag on both front wheels (or all four wheels on 4-wheel disc brake systems) start by loosening the master cylinder away from the vacuum booster by at least. “This step checks for anything in front of the master cylinder that would be preventing the master cylinder piston from fully releasing.
  2. If the wheels release the stoplight switch adjustment should be checked. Either follow the manufacturer’s procedures or continue with the next step.
  3. Deuplicate the wheel drag and then loosen the locknut on the stoplight switch.
Locknut style

4. Back the locknuts off to move the stoplight switch away from the brake pedal. Check the brake drag. If wheels released then stop light switch was source of problem. If wheels did not release see page 96 for more information.

5. Adjust the switch by using the locknuts to position it to a point where the plunger is depressed (verify by checking if brake lights are off) making sure pressure is not being applied to brake pedal that would prevent release.

Stoplight switch

Ratcheting Plunger Type (Image Below)

Ratchet Style

1. Verify complaint – if there is drag on both front wheels (or all four wheels on 4-wheel disc brake systems) start by loosening the master cylinder away from the vacuum booster by at least. This step checks for anything in front of the master cylinder that would be preventing the master cylinder pistons from fully releasing.

2. If the wheels release, the stoplight switch adjustment should be checked. Either follow the manufacturer’s procedures or continue with the next step.

3. Remove stoplight switch from mounting bracket. This usually involves rotating it 90 degrees in one direction or the other.

4. Pull the plunger out to its full length. (See below)

Ratchet style extended plunger

5. Insert the stoplight switch back into its bracket while holding the brake pedal in the full released position.

6. Verify proper operation of brake lights.

NOTE: There are other variations of switch adjustments used so it may be necessary to consult the service manual. Always verify proper brake light operation.

NOTE: Cruise control switches can also be the source of the same problem on certain vehicles.

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How to Diagnose Side to Side Premature Pad Wear on FWD Vehicles

How to Diagnose Side to Side Premature Pad Wear on FWD Vehicles

This article will focus on inner and outer brake pads that wear out faster on one side than the other. This problem can be caused from a variety of sources. In fact, the list of causes is actually quite a bit longer than most technicians know. Due to the lack of knowledge it can be easy for a technician to fall in the trap of trying to fix a part that is already functioning properly. In order to help with this, we’ve created the following list of possible causes.

Possible Causes for FWD Pad Wear

  • Sticking caliper piston on side with problem
  • Check valve brake hose on side with problem
  • Restriction in ABS modulator preventing fluid release on circuit with ear problem
  • Opposite side brake hose with restriction
  • Air in opposite hydraulic circuit from problem (i.e. left pads wearing, air is in RF/LR circuit)
Brake diagram showing percentages of each brake pad

FWD Pad Wear Solutions

As with virtually any other mechanical problem, an accurate diagnosis is the first step towards fixing and preventing premature pad wear. As a guide, we’ve prepared the following directions to help those that encounter FWD pad wear. To begin, an accurate diagnosis of the problem involves 2 components. The first is approaching the problem with a complete list of potential causes (listed above). The second is applying a logical approach to the diagnosis (listed below). 

Diagnostic Approach

  1.  Check the brake pedal height and judge it against similar vehicles. If the pedal has excessive travel or feels spongy, bleed and flush the entire system paying close attention to the circuit opposite the side where pad wear is occurring.
  2. Test drive the vehicle and get the brakes up to operating temperature. Raise the vehicle on a lift and check for wheel drag on all four wheels paying close attention to the side where the pad wear is taking place. *NOTE: If the vehicle cannot be driven due to metal to metal wear, the system will have to be restored to a functioning state before a complete diagnosis can take place.
  3. If the vehicle pulls to the side where pad wear is occurring,  the opposite side brake hose may be restricted. If no other causes of the pull can be determined then brake hose replacement should be suggested. *NOTE: Many FWD vehicles will NOT pull with a side to side brake imbalance due to negative scrub radius (See Image Below). If the vehicle does NOT pull, it does not guarantee the opposite side hose is not restricted. If pressure gauges or clamping plate gauges are available, they should be used to determine side to side braking balance. However, if not available, a good practice is to perform all other repairs and instruct the customer to return after driving a similar distance as they did without the problem. Inform them that the opposite brake hose may still be an issue and this step will determine if it is necessary.

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Policy on Premature Pad Wear

Policy on Premature Pad Wear

Allowing customers to leave the shop thinking the problem is fixed when it is not can be a problem. As a result, customers will sometimes end up returning when brakes are metal to metal. This article aims to help solve this issue. By finding and sticking to a good brake policy you can help ensure that the cause brake problem is actually fixed. At times the cause of the premature pad wear is obvious and no additional steps should be needed. On the other hand, if the cause is less than obvious or there is any question about whether the repairs that were performed will correct the problem, then follow the steps below.

close up image of car brakes

Brake Policy Steps

    1. Research how many miles and how long it took to cause the premature pad wear. Take the time and mileage and divide it by 2.
    2. Explain to the customer you would like them to bring the vehicle back for a quick check in the half mileage calculated in step number 1. For example, if the left side pads are wearing out in 5,000 miles, have the customer stop back at 2,500.
    3. After customer leaves, put a reminder to call the customer in your appointment book on the date that represents the time it took the wear to take place.
    4. If the customer doesn’t return by the date in the appointment book, give them a reminder call about the checkup.

Bonus Tip: Using this technique may save you having to replace rotors free of charge.

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How to Diagnose Premature Even and Taper Pad Wear

How to Diagnose Premature Even and Taper Pad Wear

As a continuation of our previous blogs, this blog will go over premature even and taper pad wear. All pads wearing evenly but prematurely can be caused by the front brakes being overworked due a rear brake problem or front caliper problems or seized metering valve. Premature wear of the outboard pad is caused when the outboard pad is not allowed to release off of the rotor properly after the brake pedal is released. To help you diagnose this, we’ve prepared the following lists and images:

Even Pad Wear (All Pads Worn Evenly)

A. Accelerated pad wear (mild)

  • Change in vehicle use from previous set of pads
  • Front to rear brake balance not correct (i.e. rear brake(s) out of adjustment, restricted rear brake hose)
  • Metering valve stuck on open position (Only applies to RWD’s equipped with metering valves)
  • Calipers not allowing proper release of pads due to internal corrosion, seal rollback
  • Inferior friction or friction not suited to vehicle use
Car tire with smoke coming from brakes

Change in Vehicle Use From Previous Set of Pads

Brake

Front to Rear Brake Balance Not Correct (i.e. rear brake(s) out of adjustment, restricted rear brake hose)

Metering valve with corrosion

Metering Valve Stuck in Open Position (Only applies to RWD’s equipped with metering valves)

Internal Corrosion

Calipers Not Allowing Proper Release of Pads Due to Internal Corrosion, High Mileage OE Calipers, Inefficient Seal Rollback

Curb with scuff marks

Inferior Friction or Friction Not Suited to Vehicle Use

B. Accelerated pad wear (severe)

  • Two Foot Driving
  • Vehicle Being Used for Commercial Application (i.e. delivery, taxi)
  • Venting not being allowed due to plugged or covered vent port in master cylinder
Feet on pedals

Two Foot Driving

Red truck with sign on top

Vehicle Being Used For Commercial Application (i.e. delivery, taxi)

Master cylinder

Venting Not Being Allowed Due to Plugged Vent Port in Master Cylinder

Braking diagram

Venting Not Being Allowed Due to Covered Vent Port in Master Cylinder

Taper Pad Wear

Top to Bottom Taper Wear

Floating/Sliding

  • Binding in bracket or knuckle (can’t release)
  • Seized in bracket or knuckle (can’t apply)

Fixed

  • Pad end experiencing wear is binding in caliper housing
  • Experiencing wear caliper piston not releasing (4 piston caliper)
  • End of pad opposite the wear cannot apply due to seized caliper piston (4 piston caliper)
  • End of pad opposite the wear cannot apply due to pad seized in housing

Inside to Outside Taper Wear

Floating/sliding

  • Brake pad is binding on worn end and can’t release
  • Brake pad is binding on non-worn end and can’t apply evenly
  • Rear disc pad with piston locatin tab – tab not aligned with piston notch

Fixed

  • End of pad experiencing wear is binding in caliper housing
  • End of pad experiencing wear caliper piston not releasing (4 piston caliper)
Rusting of caliper housing casting hole

Rusting of Caliper Housing Casting Hole

End of pad experiencing wear is binding in bracket or knuckle

End of Pad Experiencing Wear is Binding in Bracket or Knuckle (can’t release)

Rear disc pad with piston locating tab - tab not aligned with piston notch

Rear Disc Pad With Piston Locating Tab – Tab Not Aligned With Piston Notch

End of pad experiencing wear caliper piston not releasing (4 piston caliper)

End of Pad Experiencing Wear Caliper Piston Not Releasing (4 piston caliper)

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How to Diagnose Premature Pad Wear on RWD and FWD

How to Diagnose Premature Pad Wear on RWD and FWD

If there is one thing we all want our brakes to do, it’s for them to last. Because there are many different types of vehicles, this post will specifically focus on RWD and FWD vehicles. For other brake pads, consider checking out one of our other blogs, here is a link to premature inboard pad wear.

RWD and FWD Problems

Because each vehicle is unique, the cause of the pad wear will be based on the type of pad wear that is taking place and the configuration of the brake system.

Premature wear of the outboard pad is caused when the outboard pad is not allowed to release off of the rotor properly after the brake pedal is released. Below, we’ve posted several pictures to help you figure out what might be causing wear on your system.

Front to Rear Split Hydraulic System

  • Piston Sticking (Symptom: Drag)
  • Brake Hose on Side With Problem With Check Valve Condition (Symptom: Drag)
  • Brake Hose Opposite Side With Problem Restricted (Symptom: Pull to Side With Pad Wear)
  • Hydraulic Restriction Higher Than Brake Hose on Side With Pad Wear Not Allowing Release of Pressure (i.e. ABS Modulator)

Images for Front to Rear Split Hydraulic Systems (RWD)

Piston Sticking

Piston Sticking (Symptom: Drag)

Brake hose on side with check valve problem

Brake Hose on Side With Check Valve Condition (Symptom: Drag)

Brake hose with rusted bracket

Brake Hose Opposite Side With Problem Restricted (Symptom: Pull to Side With Pad Wear)

ABS modulator

Hydraulic Restriction Higher than Brake Hose on Side With Pad Wear Not Allowing Release of Preassure. (i.e. ABS Modulator)

Diagonal Split Hydraulic System

  • Piston Sticking (Symptom: Drag)
  • Brake Hose on Side With Problem With Check Valve Condition (Symptom: Drag)
  • Brake Hose Opposite Side With Problem Restricted (Symptom – Pull to Side With Pad Wear)
  • Hydraulic Restriction Higher Than Brake Hose on Side With Pad Wear Not Allowing Release of Pressure (i.e. ABS Modulator)
  • Air in Opposite Hydraulic Circuit Than Side With Wear

Images for Diagonal Split Hydraulic Systems (FWD)

Hydraulic Circuit

Air in Opposite Hydraulic Circuit than Side With Wear (i.e. LF inner and outer pads worn, air in RF/LR circuit.)

Vent port

Vent Port Plugged or Covered on Hydraulic Circuit with Pad Wear

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How to Diagnose Premature Inboard Pad Wear

How to Diagnose Premature Inboard Pad Wear

Premature brake pad wear can be a nuisance. The last thing anybody wants is to have to frequently replace their brake pads. Unfortunately, there are many different problems that can lead to this. Because of this, we’ve put together a list of potential problems to look for when replacing pads. This blog specifically addresses inboard wear, for outboard check out our other blog here.

Inboard pad wear

Premature wear of the inboard pad is caused when the it is not allowed to release off of the rotor properly after the brake is released. This can easily cause premature wear, and it is a good idea to learn what the potential causes are. Use the following list and images to help diagnose the pad condition.

Floating/Sliding

– Caliper housing seized on slide pins

– Inboard pad binding in bracket due to corrosion

– Inboard pad binding on slide rails due to corrosion or slide rail wear

– Caliper Piston not releasing properly

Fixed

– Inboard piston(s) not releasing properly

– Inboard pad binding on pins or in housing 

Pad Wear From Floating Caliper Causes

Pad wear shown by caliper housing seized on slide pins

Caliper housing on slide pins

Inboard pad binding in bracket due to corrosion thus causing pad wear

Inboard pad binding in bracket due to corrosion

Inboard pad binding on slide rails with corrosion and slide rail wear

Inboard pad binding on slide rails due to corrosion or slide rail wear

Caliper piston

Caliper piston not releasing properly

Sliding Caliper Causes

Caliper housing after having seized due to corrosion of the caliper hardware

Caliper housing seized due to corrosion of caliper hardware

Inboard pad binding in knuckle

Inboard pad binding in knuckle due to corrosion

Caliper piston with corrosion

Caliper piston not releasing properly

Fixed Caliper Causes

Inboard piston not releasing (mechanical)

Inboard piston not releasing (mechanical)

Inboard pad binding on pins in housing

Inboard pad binding on pins in housing

*Seized slides or a sticking inboard brake pad should be checked before thinking about a sticking caliper piston

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How to Diagnose Premature Outboard Pad Wear

How to Diagnose Premature Outboard Pad Wear

Nobody wants their brakes to wear out prematurely. When they do, a vehicle owner loses money, and time. That is why it is important to do everything you can to help prevent early pad wear. The first step to preventing this, is to know the system. Because there are many different brake systems, it is necessary to first take a good look at the configuration of the system. One you’ve identified the system, you can then start looking at different parts. To help you do this, we’ve created a list of potential causes below.

Outboard Pad Wear

Premature wear of the outboard pad is caused when the outboard pad is not allowed to release off the rotor properly after releasing the brake pedal. To fix this, the list below goes over the most common issues that arise when dealing with outboard pad wear.

A. Floating Caliper

– Rusting of casting hole – reduces diameter

– Corrosion of slide pin

– Lack of lubrication

– Caliper housing binding in knuckle (insufficient clearance)

– Pad binding on slide rails due to corrosion or slide rail wear

B. Sliding Caliper

– Corrosion of sliding hardware

– Incorrect lubrication

– Corrosion of caliper housing/steering knuckle

C. Fixed Caliper

– Outboard piston(s) not releasing (mechanical)

– Outboard pad binding on pins or in housing

A. Floating Caliper Pad Wear

rusting caliper housing casting hole

Rusting of casting hole – reduces diameter

Corrosion of slide pin

Corrosion of slide pin

Lack of lubrication

Caliper housing binding

Caliper housing binding in knuckle (insufficient clearance)

Outboard pad binding in bracket due to corrosion

Pad binding on slide rails due to corrosion or slide rail wear

B. Sliding Caliper

Corrosion of sliding hardware

Corrosion of sliding hardware

Incorrect lubrication

Corrosion of caliper housing steering knuckle

Corrosion of caliper housing/steering knuckle

C. Fixed Caliper

Outboard piston(s) not releasing

Outboard Piston(s) not releasing (mechanical)

Outboard pad binding on pins or in housing

Outboard pad binding on pins or in housing

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How To Do A Quality Brake Job

How To Do A Quality Brake Job

Most brake comebacks result from not paying attention to detail when performing the job. Taking a few extra minutes when performing the service will help eliminate the vast majority of come backs. It sort of follows the old saying “pay me now or pay me later”. The difference is paying now involves only a few extra minutes per job and paying me later involves a few extra hours. Below is a list of one great way to ensure a brake job well done:

1 - Bleeding

Where possible, open the bleeder when retracting caliper piston. The brake hose can also be line locked as an extra precaution (use only approved line locks). These steps will prevent back flushing dirty fluid through the system. If it is not possible to open the bleeder screw, push the caliper piston in slowly to prevent building back pressure. Taking approximately 60 seconds to push the piston back in will reduce the back flush pressure to a safe level. When using this step it will be necessary to drain some fluid from the master cylinder reservoir. Either step will reduce the chances of potential damage to the ABS modulator, brake valves or master cylinder.

2 - Check the Brake System

Check all hardware and replace as needed. Weak or worn hardware is a leading cause of uneven and premature pad wear. Restoring the hardware to proper working condition will help to ensure even pad wear and longer pad life.

3 - Cleaning

Clean and lubricate all contact points. Metal to metal contact points should be lubed with Moly Lube. Only a small amount is needed to do the job correctly. Metal to rubber parts should be lubed with a high quality silicone lube. The silicone will not damage the rubber parts and helps to form a moisture barrier.

4 - Machining

If resurfacing the rotor(s) use proper machining techniques and make sure the lathe is in good working condition. On hub-less rotors make sure to clean the mating surfaces with an appropriate tool. Scratch cut all rotors to ensure accurate setup. Always use sharp bits and a vibration damper when machining. After machining apply a non-directional finish using 120 grit drywall sandpaper on a rubber sanding block for 60 seconds per side.

5 - Installing

Clean the rotor before installing on the vehicle to prevent machining dust from contaminating brake pads. The best method to accomplish this is to use a mild soap and water solution. Wash both friction surfaces and wipe dry with a clean lint free rag or paper towels. If using brake cleaner, use a little more than usual and wipe the surface with a clean lint free rag or paper towel while it is still wet. NEVER use petroleum based cleaners because they leave residue.

6 - Hub-less Cleaning

Before installing hub-less rotors, clean the hub mating surface using an appropriate tools(s). Failure to properly clean this surface can prevent achieving the proper install runout.

7 - Indexing

When installing new or machined hub-less rotors the installed runout should be checked. Using spacers on the studs tighten all lugs to the proper torque using the correct sequence. If runout is not less than manufacturer’s specification, index the rotor on the hub to achieve the lowest amount of lateral runout. Before indexing mark the high spot on the rotor and hub. Indexing involves removing the rotor and rotating it one or two lugs and re-installing. Repeat this until the installed runout is below specification. If runout is out of specifications and does not change as the rotor is rotated check to see if the hight spot moves with the rotor or stays with the hub. Failure to install the rotor with installed runout less than manufacturer’s specification is the leading cause of reoccurring pulsation comebacks

8 - Torque

Properly torque the wheel lugs using either a hand torque wrench or torque stick sockets. When torquing wheels use a step torque process. To step torque the lugs tighten all lugs to half the normal torque using proper sequence and then fully torque lugs using same process. Make sure your impact has been calibrated before using torque sticks.s

9 - Test Drive

Test drive the vehicle to ensure proper operation and to break the new friction in. To break the friction in make 10 to 20 stops from 30 M.P.H. down to about 10 M.P.H. Allow about 30 seconds in between each stop for cooling. This process will properly mate the new pads to the rotor surface.

10 - Return Vehicle

Deliver the vehicle and instruct the customer that they should try and avoid panic stops and not tow heavy loads for the first 200 miles.

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Diagnostic Technique – Symptoms versus Problems

Diagnostic Technique – Symptoms versus Problems

Not using the correct diagnostic techniques can make it difficult to find the actual cause of a problem. This is important because most problems will have more than one possible cause. The use of the process shown below is a good first step in learning to diagnose successfully. When the list of possible causes has been established the next step involves finding which one is at fault. One effective technique to determine a cause is to find the symptoms associated with each possible cause and create a list. Most conditions have related symptoms. These symptoms are an effective tool when used properly.

Diagnostic Technique Example:

To better understand this system of diagnosis, notice the example below. Here we will use a RWD vehicle experiencing fast pad wear on only one side. Both inner and outer brake pads on on side are wearing much faster than the pad on the opposite side as shown:

two brakes side by side

Using a diagnostic approach we would come up with the following list of possible causes:

– Sticking caliper piston on side with pad wear problem

– Check valve brake hose on side with pad wear problem

– ABS modulator not allowing fluid release on side with pad wear problem

– Restricted brake hose on side opposite the side with pad wear problem

– Hydraulic restriction higher than brake hose on side opposite side with wear problem.

If we take the same list and add the symptoms each condition would generate we have the following:

1. Sticking caliper piston

2. Check brake hose

3. ABS modulator

4. Restricted brake hose

5. Hydraulic restriction higher than brake

1. Wheel drag

2. Wheel drag

3. Wheel drag

4. Pull to side with pad wear

5. Pull to side with pad wear

Armed with the list above, the first step in any diagnosis would be a test drive. A test drive would allow for a check for a pull and make sure the brakes are at operating temperature. This could be important in duplicating the drag associated with items number 2 & 3. Using the technique of looking for supporting symptoms is one of the most effective diagnostic techniques available.

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Generic Diagnostic Approach

Generic Diagnostic Approach

One common problem among technicians is misdiagnosing. Doing so results in comebacks that can turn into a major problem, especially if there are too many of them. Not following a structured approach to the diagnosis of a system is one of the chief causes for a misdiagnosis. In this blog, we will discuss several ways to improve your accuracy at finding and diagnosing an issue.

System of thought

One of the best ways to combat misdiagnosing is to create a systematic approach to finding the problem. One such system can be found below:

1. Determine the system

2. Think about how it operates

3. Think about the problem

4. Generate a list of possible causes

5. Diagnose and inspect in a logical manner

Thinking Man

Digging Deeper

Now that you’ve read the steps above. Lets dig a little deeper into each step.

1. Determine the system:

All systems are not the same, and treating them the same can quickly become a problem. Because each vehicle is equipped differently take some time to identify the system that you are working on.

2. Think about how it operates:

This step takes the information from step 1 and applies it to the system’s operation. Because of the variety of parts and problems you could face, it is important to understand how the system you are looking at works. Try to take each part into mind and think about how they all work together.

3. Think about the problem:

At this point, you should be starting to find the part of the system that is defective. Focus on that area and try to discover what is causing the issue. More than likely you’ll be able to find other parts of the system that are affecting what you are working on.

4. Generate a list of possible causes:

Most problems you diagnose will have more than one possible cause. Two common mistakes at this stage include approaching the issue with an incomplete list, and or adding items to the list that can’t cause the problem.  An example of this would be adding the master cylinder to our list for a low brake pedal. Conventional master cylinders cannon cause a low brake pedal.

5. Diagnose and inspect in a logical manner

If steps 1-4 are done correctly this step should be simple. Steps 1 to 4 will allow you to generate a flowchart that will lead you to pinpointing which part of the system is causing the problem.

Understand your system

To put it more simply, understand the system you are working on. By knowing the system, you can identify all possible causes, and find out witch one is causing the problem. By sticking to this process religiously you’ll find that you are misdiagnosing less and less. For more help and interaction with mechanics of all skill levels, join our facebook group “Mechanic Mafia” on Facebook. Just click the button below.

Wasting Time Solving a Problem?

Wasting Time Solving a Problem?

There you are, slaving away trying to fix something hour after hour. You’ve tried everything you can think of, and nothing works. Just when you are about ready to give up, you realize something. You shake your head in disbelief, surely you’ve thought to check the simple things already right? Wrong. Turns out your whole problem could have been fixed in mere minutes!

Saving Valuable Time

If this is a situation that happens to you, (and lets be honest, it happens to all of us.) then this blog is meant for you. It can be easy to get in the habit of trusting your memory, though often times, that is what leads to spending unnecessary amounts of time wasted. In fact, many problems have a direct answer and the can be found on the manufactures TSB’s (Technical Service Bulletin). These bulletins can make the difference between wasting time, and making money. By learning how to utilize them, you help ensure a timely job well done. 

Frusterated Mechanic

Steps of Action

Manufacturers constantly publish TSB’s that explain a problem and its solution. There are even thousands of TSBs on brakes alone. This means that reliance on the written or electronic word is increasing everyday. Accessing this information should be incorporated into the service process. The process should proceed as follows:

  1. Customer interview 
  2. Check vehicle for existing TSBs 
  3. Test drive
  4. Inspect & diagnose
  5. Perform repairs

Incorporating the check for TSBs at this stage in the process will allow you to include any road test tips the TSB may provide in your test drive. Some TSBs provide information on how best to duplicate a problem and what to look for during a test drive.

Many shops wait until they are in trouble before checking for TSBs. This is a mistake. The sooner you have the information the better off you will be. Many of the fixes listed in the TSBs will never be able to be duplicated in the field regardless of the amount of time and effort put forth. Having the information before you perform your diagnosis will save time and effort. With so much information available and access to this information being made easier every day, why not use it to same time, headaches and frustration? 

 

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Brake Technician Vs Parts Changer

Brake Technician Vs Parts Changer

Brake Technician Knowledge

What happens when you diagnose a problem by trying to throw parts at it instead of diagnosing it correctly? Does this happen in your shop with some of your technicians? What is your customer’s reaction to this problem? The majority of people servicing brakes have obtained most of their knowledge on the job. While hands on experience is sometimes the best teacher, it cannot always provide the knowledge that is necessary to understand the inner workings of the various brake parts and systems. Without this understanding, accurate diagnosis can be extremely difficult if not impossible.

various auto parts

Brake Systems

In the eyes of most technicians and consumers, the brake system is relatively simple. Disc brakes in the front and drum or disc brakes in the rear. “Throw” a set of pads on it and it will be fine. This oversimplification of the brake system leads to many of the problems that are encountered. The brake system is a complex system. It has many components which are dependent upon one another to function properly. The key word is “system”. They work together to stop the vehicle. When one part of the system is not working properly, then other parts of the system will be affected. There is a direct relationship between how good a technician is and how much they know about how each part in the system works. Correct and accurate brake system diagnosis depends on having a clear understanding of:

  • how each part works…
  • what can go wrong with it….
  • and what it does.

Knowledge is key

Many technicians servicing brake systems do not have a good enough handle on the first point listed above, how each part works. Without this the technicians will be faced with replacing parts to try and correct a problem. This is the definition of a “parts changer”. Brake technicians have a clear understanding of each part in the system and how it relates to the overall system operation. This gives them the ability to understand what can go wrong with the part and what it will cause. They use this in applying a logical approach to the diagnosis of the various brake problems they encounter.

Technicians must constantly seek out new sources of information. These tips and blog posts are examples of where to get the kind of information necessary to allow accurate diagnosis of many different brake problems. Other resources include trade publications, seminars, webinars, and the internet (many resources here with YouTube, Facebook, Automotive Forums, etc…). With the constant advancement of vehicle technology, the learning process will never be over. We hope that you will keep coming back for our Tech Trick Tuesday Blog Posts.

 

Mechanic Community

For one on one help, join the Facebook group “Mechanic Mafia”. There are many mechanics of all skill levels ready to help answer questions and interact. You can check it out by clicking the button below:

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