Brake rumble

[Russ]

Just became conscious of this: when I apply the brakes at a speed over 40 mph, there is a faint but distinct rumbling sound & sensation. I wouldn't call it a shudder. The best way to describe it is that when the brakes are applied it suddenly feels like the car is travelling over rough pavement. There is no pull left or right, and it seems to be coming from the rear. The rotors look fine and there is plently of pad. What else should I be looking for?

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Russ
'91 black/black

[This message has been edited by Russ (edited 30 October 2002).]

 

[nsxtasy]

It could be a very slight warpage, or it could be deposits of brake pad material on the surface of the rotor. In either case, if you have the rotors turned (being careful to remove as little material as possible to make them flat), it should go away.

This is more common in the front than in the rear...

 

[nsxlover]

I have the same problem with mine. When I get it back I am going to try to have the rotors turned. I also notice it more if I am driving it hard and the brakes are getting hot.

 

[nsxtasy]

Originally posted by nsxlover:
I have the same problem with mine. When I get it back I am going to try to have the rotors turned. I also notice it more if I am driving it hard and the brakes are getting hot.

If it only happens when the brakes get hot, that is a classic sign of "brake shudder". As noted in the FAQ, brake shudder occurs when hot spots develop on the rotor. This phenomenon means that different spots on the rotor expand with different heat coefficients, so that the rotor is flat when cold, but not flat when it gets hot. I had ongoing problems with brake shudder on my mostly-tracked car. It would go away if I replaced my rotors, but would re-appear after a couple of track events, and become unbearable after a couple more. It finally went away for good when I installed cooling ducts, as well as using aftermarket pads and rotors.

Turning the rotors is fine for a street-driven car, which is why I suggested it for the first example given. For a car that is going to be driven on the track (or otherwise driven hard), the downside of turning the rotors is that it makes them more susceptible to shudder problems.