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Brake squeak...

Jim B

Well-known member
Joined
Feb 26, 2006
Messages
62
Location
Illinois
Corvette
1974 L82 Grey coupe
Brakes were rebuilt within the last year. And this summer there is a rotational squeak while driving (most of the time). They work fine but it is annoying. I can't find anything, and took it to my mechanic. He's not sure why either. Help please!
 

Vettehead Mikey

Well-known member
Joined
Aug 26, 2003
Messages
3,486
Location
Not that far from Ottawa
Corvette
1973 Coupe
If the squeaking stops as soon as the brake pedal is pressed, the cause is usually from the pads being moved laterally and rubbing on the retaining pin. A tiny dab of high temp grease might stop the noise for a while. The root cause of the pads moving is usually excess rotor runout.

If the noise occurs when the brakes are applied, there are anti-squeal shims available.
 
Last edited:

Jim B

Well-known member
Joined
Feb 26, 2006
Messages
62
Location
Illinois
Corvette
1974 L82 Grey coupe
It goes away when the brakes are applied. I thought it might be rotor run out. How do I correct it? Or should I find a mechanic that can take care of it? Makes me crazy.
If the squeaking stops as soon as the brake pedal is pressed, the cause is usually from the pads being moved laterally and rubbing on the retaining pin. A tiny dab of high temp grease might stop the noise for a while. The root cause of the pads moving is usually excess rotor runout.

If the noise occurs when the brakes are applied, their are anti-squeal shims available.
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,453
Location
CenCoast CA
Corvette
71 04 12 19
C2/3 brake rotors which actually have runout are rare. Yes, it does happen, but those rotors are pretty robust so it doesn't happen often.

What is more likely than rotor runout is that, at sometime in the car's life, the rivets holding the rotors to the either the front hubs or the rear axles have been drilled out, so the rotors can be removed.

What's important to understand about C2/C3 disc brakes is the rotor friction surfaces were machined after the hubs and rotors were assembled. The assembly is "true" but the hub and/or the rotor, individually, may not be. The rear rotors' friction surfaces were machined after the rotors and the axles were assembled. Again, the assembly is true, but the axle flange and the rotor flange may not be.

This dumb-assed way to manufacture C2/C3 rotor/hub and rotor/axle assemblies has created havoc with servicing those cars' brakes.

You can have a perfectly machined friction surfaces on used rotors which were "turned" or on new rotors, but if the two mounting flanges–hub or axle and rotor–are not perpindicular to their axes, then "rotor runout" occurs.

Another probmem is can be with the rear wheel bearings on C2/C3 disc brake cars. You can have true axles and rotors but if the wheel bearings are too loose, you'll have brake problems such as the OP describes.

What are the solutions? There are many. Shims can be used to "fix" a problem with untrue mounting flanges on hubs, axles or rotors. You can press out the wheel studs then machine the hubs and/or axles to "true" them. You can rebuild your rear bearings such that you have the absolute minimum acceptable bearing clearance.

There are more details in some old articles here on the CAC about C2/C3 disc brake service.
Click here or click here
 

Vettehead Mikey

Well-known member
Joined
Aug 26, 2003
Messages
3,486
Location
Not that far from Ottawa
Corvette
1973 Coupe
It goes away when the brakes are applied. I thought it might be rotor run out. How do I correct it? Or should I find a mechanic that can take care of it? Makes me crazy.

Very, very few mechanics had a clue about C2/C3 brakes even when the cars were new. It's worse now. Probably some previous owner replaced the rotors not knowing that the hub/spindle are a matched set.

Hib provided some good ideas above.

First thing to do is establish if the rotor surface has unacceptable (>.008") runout or not.
 

Jim B

Well-known member
Joined
Feb 26, 2006
Messages
62
Location
Illinois
Corvette
1974 L82 Grey coupe
Thanks guys! Is there a tool to measure runout?
Very, very few mechanics had a clue about C2/C3 brakes even when the cars were new. It's worse now. Probably some previous owner replaced the rotors not knowing that the hub/spindle are a matched set.

Hib provided some good ideas above.

First thing to do is establish if the rotor surface has unacceptable (>.008") runout or not.
 

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