The reason every "Ultimate brake test" comparison is won by the 911 series Porsches (For the last 40 years), is because of the rearward static weight bias of the rear engine. It might have been ugly in the corners (911 trailing throttle oversteer) but under braking, the weight shifted to 50/50 front/rear and the cars just stopped. The bigger tires on the rear just allowed more mechanical traction to balance some of the weight transfer. The same applies to the Corvair. There is no reason to run smaller piston calipers on the rear, unless you are dictated by either rules or availability. I retained a front/rear balance bar on the race car, but used the same calipers/rotors front rear. The balance bar will allow "tweaking" of the front/rear, if needed. But I use the same size master cylinder on the front calipers and on the rear. Stops straight.

Seth Emerson

Check my new Performance Corvair Web site: [www.perfvair.com]

Located in lovely San Jose, California

Thanks Seth, for letting me know that I was not crazy! When I was buying things for my set-up, I figured the brake bias on maximum braking would be pretty close to 50/50 on a Corvair (depending on the static weight distribution). But in no case could I see a Corvair needing less braking at the rear than the front like a front-engined car.

Jonathan Knapp
Wheeling, WV
'66 Corsa Autocrosser

Follow up.

I went with the Wilwood twin piston calipers. I thought I post some note on my experience.

Recap on brake set up
Stock rear drums
71 Chevelle disc drum MC, 1" bore
Adjustable brake proportioning valve on rear circuit
16 in steel rally rims, 205 front, 225 rear summer tires
Wildwood aluminum twin piston gm metric calipers mounted to the rear
Scarebird brackets
S10 rotors
Cadillac brake lines (longest Scarebird recommends)

Overall, very happy I did it. I've put about 5000 miles on the car since the upgrade. The only relevant comparison I can make it to my 86 Corvette and I'd say my corvair is better, the biggest difference being fade (some vs none)

There were issues (no particular order and I'll post photos)
1. Bracket alignment. I filed the bracket to make it fit. I am positive that if I had used the OEM style cast iron calipers, I would not have had this issue
2. Pin bolt alignment. I think this is typical of the GM metric caliper/S10 rotor/Scarebird bracket combo. I put a washer under the spacer for piece of mind
3. Interference between the inside (yes inside) of the caliper and rims. I added a wheel space for clearance

Other things to note are
1. The bajo bolt on the caliper comes close to the frame but it's clear. I have the quick ratio arm so the inside wheel doesn't turn in as much as stock at full lock. OEM steering arms might have been a problem
2. The long lines Scarebird recommended were required. Any shorter would have been a problem.
3. The adjustable proportioning valve has been useful. I'm somewhere in the middle. The rears were locking up but at the moment it pretty balanced.

James
65 Corsa
SF Bay Area

Photos of the caliper and bracket interface. I'll try to post pics of the filed bracket (too big at the moment)

James
65 Corsa
SF Bay Area



Edited 1 time(s). Last edit at 01/15/2023 02:04PM by jamesolefjensen.

Bracke line routing and bajo bolt clearance

James
65 Corsa
SF Bay Area

MC and proportioning valve

James
65 Corsa
SF Bay Area

Congrats! Did you have any rubbing between the back of the wheel and the face of your calipers? I struggled with that for a while until I found Rocket Racing.

Daniel Atkinson
Tacoma, WA
65 Turbocharged Corsa

Yes, the caliper did rub against the wheel. My photo of the problem is still too big (hard to downsize on my phone). The Wilwood caliper sits proud of the rotor hat/wheel mounting surface and my rims are bulky near the lug nuts. . The rubbing was on the surface of the caliper closest to the wheel centerline (if that makes any sense; wish I could post the photo). I added 1/4" spacers to fix the problem. I think the cast iron OEM style caliper are flush with the rotor hat and wouldn't have this problem.

James
65 Corsa
SF Bay Area

Here are photos showing the other end of the bracket and how it interferes with the caliper and how I filed it to fit.

James
65 Corsa
SF Bay Area

Here's another photo showing the banjo bolt to frame clearance (near spring pocket). The washer under the caliper pin bolt spacer can be seen also. Without it the head of the bolt is about flush with the caliper surface.

James
65 Corsa
SF Bay Area

Her are photos of where the caliper and rim were rubbing (witness marks) and the spacer I used to get clearance. I happened to have this set but probably could get away with a thinner set (I think they are 1/4" thick)

James
65 Corsa
SF Bay Area

Perseverance counts, James. The install looks great. I used the SSBC calipers (as shown in an early photo.) I had no wheel clearance issues, I bet that is based on the drop center of the steel wheel. I have never put steel wheels on my car. I actually installed a set of 14" 3-piece bolted wheels over the SSBC calipers and they cleared (just). I had to turn the wheel bolts around to move the nuts to the outside to clear the caliper.

Seth Emerson

Check my new Performance Corvair Web site: [www.perfvair.com]

Located in lovely San Jose, California