Rear disc on a 68 Firebird

[ho428]

I'm putting rear disc on my 68 using 4 Piston Camaro Calipers since they have the 1 7/8" pistons, I have the 2 1/16's Firebird Calipers up front.

Has anyone done this?

It looks like finding a rotor will be an issue, I may need a front drop hat type rotor with a 2 1/2" flange to rotor centerline dimension and turn the axle flange down for it to slip over, not concerned about a parking brake since it's a race car. But because of the 11" rotor size and the caliper being so large it's not going to be as easy to mix and match as I'd hoped.

I haven't been able to find a rotor website that I can search by size, only year, which does not help.

As you can see the OEM front has a relief for caliper clearence, the rear axle flange is about 6.2" I need about a 6" OD rotor hub to clear the caliper, so I thought a later style drop hat may work and turn the flange down.

[LONE*STAR]

I am in process of doing the c5/c6 swap. Mostly oem parts execpt for the adapter brackets and lines, all you really need to do is turn down the axles and a drum hub(will fit disk spindle) to 5.94. This way you have all matching components. Tobin @ Kore3.com was a huge help in my planning.

[ho428]

Becasue of Vintage Class racing rules I have to run period correct brakes, mainly the Calipers, on rotors we have some leeway.

Going thru the catalogs at the parts store yesterday yielded nothing, to many rotors listed and not enough dimension on any of them.

Looks like this will be a tough search.

[Tito]

Have you looked into the circle-track stuff? Stuff like this from Speedway might work (?):
http://www.speedwaymotors.com/11-1-2-Inch-Rear-Rotor,23464.html

The other rotor that comes to mind is the 68-ish vintage corvette rotors, but they're 11.75" diameter and 1.25" thick (Not sure if the calipers you plan to run are for 1" wide or 1.25" wide rotors...)

Recall that GM essentially used the 68/69 corvette rear brakes (rotors & calipers) on the JL8 rear disc setup they ran on the Trans Am Z28 cars. I'd certainly look into that.

Another option would be to go to a 2-piece rotor, but I'm not sure if that would be legal in the vintage class or not. I think you can get a bolt-on hat with darn near any offset you want, but I"m not sure if there is an "off the shelf" 11" rotor.

[Apogee]

Becasue of Vintage Class racing rules I have to run period correct brakes, mainly the Calipers, on rotors we have some leeway.

Going thru the catalogs at the parts store yesterday yielded nothing, to many rotors listed and not enough dimension on any of them.

Looks like this will be a tough search.

If you're running the C3 Corvette rear caliper (same as the 4-piston used on the JL8 Camaro, is it not?), why not just run the C3 rear rotors? The center bore is slightly larger at 2.813 than the standard Firebird 2.776, but nothing you couldn't take care of with a centering ring. Just as a side note, the C3 rear rotors are the same castings as the front, just machined slightly differently with respect to the hat thickness.

Aren't most vintage guys running the C3 4-piston fronts as well in order to get the thicker, heavier-duty rotor? Is that not in the budget to do here?

Tobin
KORE3

[ho428]

I've seen a few cars run Caliper spacers to widen them out for extremely wide rotors and run the two piece hat and rotor.
It looks to me like they are running the 11.75 dia rotors as well.

My Calipers for the rear are meant for 1" thick 11" dia. rotors since they are actually OEM front Calipers.
I found some 11" at .8125 thick rotors with the correct backspace in stock at NAPA, just have to re-drill the bolt circle for 4.75, with new pads on the rear I should be ok for awhile.

Haven't mocked it up yet, clearing the inner hub will be tight and I will have to make a mounting bracket, and the shock will be very close on the DS since my car still runs staggered rear shocks.
Other than all that what could go wrong?

Pic is of the Sunoco Camaro brakes. It has about the same set up on the rear.

[Apogee]

If you need an 11 dia x 1" thick rotor, have you considered the 1979-1981 Firebird rear rotor? It's 5 x4.75 x 2.776 and while it's 11.172" in diameter, that's something you could easily remedy in a lathe if needed.

Tobin
KORE3

[ho428]

I measured one, the backspacing didn't seem deep enough for the caliper front to clear the back of the rim.

I had to grind the outter part of the caliper casting down about 1/8" using the 3" backspace rotor up front and 15" rally rims.

If this rotor I picked up doesn't work out though I might have to look at the Firebird Rotor again and get a different offset rim and run a spacer. Either that or go to a different rim all together.

The worst part is having to get so many different combos of parts to try, it's not like you can return this stuff once you work with it.

Email sent