Rear brake drag can be an annoyance, and one that can get you in the kind of danger that every driver wants to keep well away from. One or both of the wheels in the rear can lock up when you press the brake pedal, usually causing the vehicle to skid, potentially resulting in an accident of some sort. The main causes of this are among the following.
- Brake shoe contamination
- Brake drum condition
- Rear brake hardware
- Friction material
- Brake valving
“Rear wheel lock-up” is a term used to describe many different problems, which you may experience with your vehicle’s rear brakes. Like any other, this issue needs to be fully understood before it can be definitively fixed, which means finding out the following things before repairs begin.
- Does the problem happen under panic, moderate, or light stopping conditions?
- Is it an axle or one-wheel problem?
- Does the problem happen upon dry roads, or just during wet or slippery conditions?
- Is the issue associated with any prior brake work?
- Does the vehicle come with a full length or diagonal-split hydraulic system?
- Does it have disc or drum brakes at the rear?
- What sort of valving is used?
There are two main classes of rear wheel lockup issues. The first is much more common, and caused by a mechanical fault in the brakes. The second type owes to hydraulic issues inside the system, which although rarer, can cause heavy complications down the line if they are overlooked.
Brake Shoe Contamination
This happens when a wheel cylinder or axle seal leaks, contaminating the brake shoes and altering its coefficient of friction. If this is mild, then the friction goes up, and if happens in a severe manner, then the friction is reduced.
Brake Drum Condition
If your car has a brake drum which varies widely in diameter, one of the wheels could lock up. The run-out would need to be measured periodically, and for that, you would need a mechanic. If you suspect a problem, install the drum on the vehicle’s other side and see if the issue persists.
Rear Brake Hardware
Return springs are not just a way your drum brakes can be released; they also play a heavy role in when the brakes engage. A weak spring would cause premature engagement, in which case you would need to get the entire rear shoe hardware replaced in order to resolve the problem.