02 Jan 2013
January 2, 2013

Rear Brake Noise

0 Comment

Rear Brake Noise
Under light braking loads and especially after fitting of new pads and or rotors it is quite common to hear rear brake noise. This will go away after time but the amount of time depends on several things.

We outline the reasons for rear brake noise in this article.

First of all to ascertain if brake noise or brake squeal is coming from the front or the rear of a vehicle it is almost impossible for you to do this yourself. It is usually best done with a second person OUTSIDE the vehicle on a safe area of quiet road listening to which end of the car the noise is coming from as the car comes to rest.

It is almost always in the last few turns of the wheels that the brake squeal will occur just as you are “feathering” the brake.

Three things are worth considering here.

1) Many modern cars are fitted with an automatic brake bias valve which limits the fluid pressure to the rear brakes when the car is only lightly loaded (few passengers). With more load the bias valve increases the pressure to the rear brakes and makes them work a little harder to undertake their share of the braking load. This helps the pads bed in faster. However extended driving with light loads dramatically extends bed in time. Some more exotic cars have a manual bias valve which only experienced campaigners will know how to adjust.

2) Rotor condition is paramount, even a small off flatness of the rotor will double bed in times or more and the rear brake noise will go on longer. Having rotors skimmed or replaced is always recommended when fitting new pads.

3) Rear rotors which have a handbrake shoe built into the rotor are the worst of all cases. These are on the rear wheels of BMW, Mercedes and Volvo cars and our research has found that the hollow and sometimes thin sections of the drum bore can cause a resonance effect and greatly exaggerate rear brake noise which in some cases NEVER goes away. OEM builders have tried all sorts of fixes, extra shims, different chamfer lengths front and rear and have in most cases come up with a solution but considering the cost of OEM parts many people end up buying lower priced aftermarket parts and find it a tough call to solve the noise issues. EBC Brakes is at the time of this article developing a new material processing method that “Deadens “ brake noise in a very unique way and we hope to launch these new generation materials during 2010. Until then in some cases rear brake pad noise will endure for 1500 -2000 miles on certain cars.