Problem: One or both rear wheels lockup during braking or the rear end of the car squats when braking.
Cause: Rear Wheel lockup or squatting has many causes. Here is the list of possible causes:
- Service and parking brake adjustment
- Rear brake hardware
- Shoe lands or bosses
- GM clip in wheel cylinders
- Brake drum condition
- Brake shoe contamination
- Brake valving
- Friction material
Solution: The description “rear wheel lock-up” can be used to describe any one of several problems with the rear brakes of a vehicle. Before any problem can be cured it first has to be understood. There are a number of important pieces of information you will need before you can begin your cure of whatever type of rear wheel lockup you are faced with. To begin with you will need to know the answers to the following questions:
- Does the problem occur under light, moderate or panic stopping conditions?
- Is it a one wheel or axle problem?
- Does the problem occur on dry road surfaces or only when the roads are wet or slippery?
- Is the problem related to any brake work that has recently been performed?
- is the vehicle equipped with a front to rear or diagonal split hydraulic system?
- Does the vehicle have rear drum or rear disc brakes?
- What kind of valving is the vehicle equipped with?
- Think about the system
- Think about how it operates
- Think about the problem
- Determine possible causes
- Apply a logical diagnostic approach
Service & Parking Brake Adjustment
Figure 61.2 Figure 61.3
Rear Brake Hardware
Shoe Lands or Bosses
GM Clip in W/C
Brake Drum Condition
Brake Shoe Contamination