I'm thinking of doing a brake conversion using the Z06 Front brakes on the back of a C4. I think it would be one heck of an increase in stopping power with 315 or 335 tires on the back.

Using a DRM bias spring or possibly the Tahoe master and a proportioning valve to control brake bias. I am in the belief that it's going to take more master cylinder capacity with 4 of those calipers.

Has anyone done this yet? What adapters has everyone been using?
What are you using for an emergency brake?

 

TJWong could probably give you ideas as he has two J55 calipers per wheel on his car. You would have to keep stock caliper in order to keep E brake. You would have to make a bracket to hold both calipers. Would also benefit putting a 13 inch rotor back there. I would also address the front to if you do this.

 

Are you also upgrading your fronts? The general rule is don't bother with the rears until you've upgraded the fronts. Because of weight transfer during braking, the fronts do something like 80% of the braking.

The C5 front caliper is slightly larger than a C4 front and way larger than a C4 rear. The Bias spring you mention will feed even more pressure to the rears. Therefore, you'll end up with a system that will engage the ABS on the rear very early under moderate braking.

By way of comparison, I have 6-piston willwood GN3 calipers on the front of my '96 and grandsport (stock 96 front) calipers mounted on the rear. I also have the DRM bias spring. With this setup, the rear brakes STILL try to lock before the fronts in some situations. I'm probably going to go back to the stock bias spring to tone the rears down a little. Obviously, it's only an issue on the track -- normal driving is fine. An adjustable proportioning valve is definitely the best way to go, though.

As far as the master cylinder, unless you do major upgrades (6-pistons, etc), the stock MC is just fine. I'm still using the stock MC and it works OK. It's border-line with my setup, but I just didn't have the cash for one of the DRM units with the built in prop valve.

In summary, unless you're going to significantly upgrade your fronts, don't touch the rears. Give DRM a call as well -- they have a TON of C4 experience and can talk through several options with you. They're generally pretty good about not trying to sell you something you don't need also.

 

That seems like good advice.

Larry
code5coupe

 

At the recent Speed GT race I attended down in portland I saw a few guys running Willwood and such 6-pots up front with C5 fronts in rear.

 

Too bad you didn't ask where they got their adapter brackets from.
I've got several years on the C5 front conversion on my vettes. I started off with the J55s on the front of the 89 and stock on the 90. I am using the DRM on the 89 and not yet on the 90.

You posted your brakes were ok with the stock MC. You have a lot of pedal travel I'd bet. That's why going to the 03 Tahoe, and maybe others, mc is a good move. Much bigger piston, less pedal travel for same stopping power.

I found a place for the rear adapters and I am going to get a set and go C5 on the rears.

THe e brake is a relatively easy fix, a high pressure ball valve, mash brakes, close valve, brakes.

 

Now that would be a cool anti-thief device. If all 4 calipers were connected.

 

Yep, I agree, but it will work almost as well with just the rears.