Help! problem w/lateral runout on disc's

[billmcd]

Does anyone know how to correct a lateral runout problem with the disc brake rotors on the REAR of 82 corvette? My brake system keeps sucking air about 10 - 14 days after it is bleed. We have identified that it appears to be coming from a RR caliper. Eckler's tech support said I have to turn the new disc's while they are bolted to the car. However, the machine that does it will not fit the rear wheel well. Any ideas how to true the rotors on the rear would be greatly appreaciated!

 

[GTR1999]

If the bearing endplay is under 003 and your only problem is runout then you can shim them to under 003. I wrote a thread on it that will help you.
I don't believe it's here so I don't want to link another forum so you can search for it or PM me.

 

[JohnZ]

However, the machine that does it will not fit the rear wheel well. Any ideas how to true the rotors on the rear would be greatly appreaciated!

Our local shop has an on-car brake lathe for doing that job that fits fine; photos below.

 

[Peer81]

This is what I did: (post #76)
http://www.corvetteactioncenter.com...y-forum/75812-original-l81-engine-pics-6.html

I believe its the same as what Gary is referring to.

Greetings Peter

 

[73shark]

Stainless Steel Brakes used to sell a circular tapered shim to handle this problem. Don't know if they still do.

 

[billmcd]

If the bearing endplay is under 003 and your only problem is runout then you can shim them to under 003. I wrote a thread on it that will help you.
I don't believe it's here so I don't want to link another forum so you can search for it or PM me.

Gary: Thanks for the info! I hadn't thought about checking bearing end play. billmcd

 

[billmcd]

This is what I did: (post #76)
http://www.corvetteactioncenter.com...y-forum/75812-original-l81-engine-pics-6.html

I believe its the same as what Gary is referring to.

Greetings Peter

Peter: Thanks for the pictures! I was wondering how you shape the shims to fit, but see that it not necessary. It's got to be fun driving a corvette there. I didn't remember seeing a lot corvettes last time I was in Amsterdam. Thanks again! billmcd

 

[Hib Halverson]

In the rear there is more than rotor runout affecting the calpers' "sucking" air. You can have the rotors with zero runout but if the rear bearings have too much end-play, the looseness will also cause the rear brakes to suck air.

In total, the 65-82 disc brake calipers can tolerate about .010" run out on a cumulative basis, ie: any combination of rotor runout, axle/hub flange runout and bearing clearance.

 

[GTR1999]

Gary: Thanks for the info! I hadn't thought about checking bearing end play. billmcd

Yes it's a good idea to check out the endplay as well. The on the car lathe John shows would work, problem is they're not too common, at least around here.
Bottom line for my cars and jobs I shoot for 002 for both endplay and runout. I never used O ring calipers,DOT5 BF, and I would say the only gimmick or trick is the shimming. I also bolt the rotors on the spindles and hubs for locked in setup.
The brakes work great, for st use I use organic pads.

Good luck
Gary