O RINGS AND ROTOR RUN OUT

[rickkkyg]

VETTE BRAKES AND PRODUCTS SUGGEST THEIR O RING CALIPERS ELIMINATE THE NEED TO SHIM REAR ROTORS ? I HAVE ALWAYS SEEN THEM SHIMMED . HERE IN JUPITER FL AND BOLTON CORVETTE CTR IN CT. ONCE SHIMMED BRAKES HELD GREAT !

COMMENTS ?

 

[Hib Halverson]

VETTE BRAKES AND PRODUCTS SUGGEST THEIR O RING CALIPERS THE NEED TO SHIM REAR ROTORS ? I HAVE ALWAYS SEEN THEM SHIMMED . HERE IN JUPITER FL AND BOLTON CORVETTE CTR IN CT. ONCE SHIMMED BRAKES HELD GREAT !

COMMENTS ?

On the rear of a 65-82, before the rotors were installed on the car, they were attached to the axles and then had their friction surfaces machined. It was done this way to eliminate any problems with the axle mounting flange not being perpindicular to the axle centerline. The downside of this comes when you drill the rivets and installed new rotors. If the original rotor machining compensated for axle flanges that weren't perpinducliar, most likely, the new rotor will have "runout" in relation to the fixed brake caliper. The easy fix is to shim the rotor.

The real fix is to true the axle.

As for o-ring calipers...they've become a common fix, especially in the rear, for 65-82 brake systems having trouble with runout.

 

[Gunther]

Hi

And it doesn't need a lot of runout for the old lipseals to suck air into the calipers.
There is no negative side to the O-ring pistons, but at least one to the lipseal design, so make your choice.

Rgds. Günther

 

[GTR1999]

Runout properly set to under 003" will be fine with lip seals. I bolt them on and dial them in and never have a problem. Many have followed my thread on this and done them at home as well. The O rings may work as an option but I always like to get the bearing endplay and runout set correctly and the cars stop on a dime.
You can find my threads on several locations to help you.

 

[Hib Halverson]

If inward piston movement is about .010 or more, the inner piston seals will suck air. In the rear that makes for a real problem as it's easy to have the cumulative effects of bearing clearance, axle flange non-perpindicularity and rotor runout much larger than that in-spite of each of those seeming to be small.

However, if you set the axle bearings to .0015 endplay (which may require surface-grinding shims), get the axle flanges 90 deg to the axle CL and have the rotors at +/- .001-.002 for runout and parallelism, you'll have killer brakes.

Admittedly, getting there is tough but that's life with fixed-caliper brakes.