Bill Dearborn

A friend stopped by the house today to see if I would help him install some rear calipers on his C4. He has C5 calipers and rotors on the front but he had a set of Brembo 4 pot calipers with two piece 12.88 rotors that he wanted to put on the back. I told him I thought he might have too much rear brake bias if he installed the Brembo's but said we should check things out before making any final decisions.

Will this setup work? The rotors front and rear are the same diameter and the rear calipers have a lot more piston surface area than the C5 calipers in the front but the pad swept area is smaller than the C5 pads. Another thing that got me besides not knowing how to get the pads out of the Brembos was the lack of a bleeder screw on the outside caliper half. How can they bleed the brakes if they don't have a bleeder screw in each caliper half?

Suggestions, comments?

Bill

Sidney004

The piston surface area is the determining factor in changing the bias.

Bill Dearborn

So the answer is he can't use these brakes in the rear while he is running the C5 calipers and rotors in the front???? Larger piston area in the rear, rear brake rotor diameter equal to the front diameter combining to give too much rear brake bias???? I know on the C6Z51 they decrease the rear caliper piston area so they don't get too much rear brake bias with the increased rotor diameter over the base brake system.

Any idea about why there is only one bleeder screw on a 4 piston caliper? How do they get the air out of the outer half of the caliper?

Bill

Kubs

What are the piston bores and pad shape of the rear setup? Is he using a stock master cylinder and stock bias spring or alternate setup? I can calculate the bias for you.

Bill Dearborn

It looks like the piston bore is about 1 7/16". The pads have numbers on them but all I can see are partial numbers on Brembo pads xxx07:5146. The pads are small about 2.25' x 4.25 ". He is using C5 front brakes, stock master cylinder and has added a brake bias spring to get more rear bias. I can't get the pads out of the calipers as I don't know the secret to releasing the two pad retaining pins. There was a spring arrangement between the two pins but I did get that out. The pins just will not push out.

Any idea how you bleed these things with only one bleeder screw?

Bill

Bill Dearborn

ttt

Kubs

Its going to be about 53% front and 47% rear with that setup. Too much rear brake in my opinion.

As far as the bleeder, if its a 4 piston caliper there should be two bleeders...

Bill Dearborn

It is a 4 piston caliper and there is only one bleeder at the top of the inside caliper half. I attached some pictures of the caliper.

Bill

rfn026

Put an adjustable bias valve in the system. This isn't an ideal setup but you deal with what you have.

Richard Newton
Newton's Laws

Bill Dearborn

I just found the for sale post for these calipers. They are for an 87 or earlier car with the drum parking brake. If my friend puts these on his 91 he is going to lose his parking brake unless I transfer the older brake system to his car. I just don't see how we can bleed these things properly with only one bleeder screw. The way I see it the brake fluid will always take the short path to the bleeder screw so will not flow well into the outside caliper half.

Bill

Kubs

Those look very similar to the GENIII Viper Brembos I just put on the front of my car.



The way the pins come out, is you tap them out with a punch from the front face (or the side that faces outward). If you look close one side has a small hole for the pins and the other side is bigger. Tap with a small punch from the small side and it should drive the pins out.

A bias valve will help, but like you said not the best solution. Putting the Z51 brackets on the front and using the 13.4" rotor will help too. The Z51 setup fit my old 17" A-molds, but not my CCW classics. I now use 18" C6 Z06 fronts with the Viper setup.

Jaguarxjr@1968

Hell all I am in a time crunch on a slamming deal for skinnies and meats in 15 inch BUT the rears are 5.5 back space will that stick out too far? TY in advance.