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.
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.
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
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.
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.
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