Why do rear brakes lock up

Any and all suggestions are appreciated. Might be a problem of some sort with the auto-adjuster, ABS, proportioning valve or the parking brake mechanism, but my money would be on the brake hose connecting the brake cylinder to the brake lines. The inner lining of these hoses sometimes detaches when the hoses get elderly and blocks the hose. Are the shoes correctly installed? Is there a leading shorter and trailing longer shoe on each side of the car with the longer shoes towards the rear?

Is The emergency brake cross-bar properly positioned between the shoes? Have you replaced the return springs and are those springs properly positioned and installed? With the drum off, have someone GENTLY and slowly depress the brake pedal while you watch the shoes being pushed out against the springs.

When the helper releases the brake pedal, do the shoes retract quickly and completely?? Our technicians understand both disc and drum brakes, as well as how all the interconnected components work together for your safety. Find Your Store. What Causes Brake Lock-Up The brakes on your vehicle are certainly one of its most important safety features. Why Brakes Lock Up There is a long list of reasons that one or all of the brakes on your vehicle might lock up.

Apply pressure to the brakes and try to gain as much control as possible. The feedback is the ABS working to keep the wheels from locking up and preventing you from skidding. If the problem moves to the opposite side then you are on the right track, if not continue your quest. If an axle seal or wheel cylinder leaks and contaminates the brake shoe s it changes the coefficient of friction. If it is mild contamination then the friction is increased while severe contamination will cause a reduction in friction See Figure A common source of contamination occurs during the installation of new shoes.

An effective method of preventing this is to put wide masking tape on all the friction before starting the job. Once complete simply remove the tape and the shoes are perfect. They are also very sensitive to the type of friction that is used. If the problem is related to rear shoe replacement and everything else checks out then consider installing a set of premium linings to fix the problem.

An important point to keep in mind when inspecting vehicles for the cause of a rear wheel lockup condition is that more than one of the above conditions could be present.

Everything matters some is a good way to look at it. Always look at the big picture when inspecting the rear drum brake system. Brake Valving The vast majority of rear wheel lockup problems will be related to the mechanical causes discussed earlier. This is a good example of where steps 1 and 2 come into play in the diagnostic process.

The only component that could cause rear wheel lockup is the proportioning valve s. View Our Most Recent Post. 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. 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? One reason could be a defective wheel cylinder, which is part of the brake system. Your parking brake cable could also be adjusted too tight. The slightest pressure on the brake pedal, will then cause the brakes to work at full force, causing the lock up.

What does it sound like when your caliper is stuck? When you have caliper issues, the brakes may be very loud when you try to stop. It can be a high-pitched screech, a thud or a metal-on-metal grinding noise. These sounds can mean that your caliper is stuck, that it has come loose or that it's having some other problem.

How do you fix a stuck handbrake? Your parking brake is stuck due to rust or corrosion. Disturb the brakes manually. Apply and release the brake a number of times. Shift into drive and reverse, and back between drive and reverse again to slightly move the vehicle back and forth. This may dislodge some of the rust. What are the symptoms of a bad brake caliper?