Brake Recommendations Please

[XfireZ51]

Sam,

Would you explain further what you mean by the C6Z brake piston volume adjusted for C5-6 but not C4?
I have the C6Z brakes, front and rears and using stock master/booster. In the 2 years of driving I have not sensed any inadequacy from them. I first had just the fronts, then upgraded the rears last year including the eBrake. I don't track the car although I have hauled it down from 225km/h+ a few times with no drama. Having enough brake is the least of my concerns. Yes they do look nice behind 18"+ wheels. One of the reasons I did it was due to limited tire availability for 17s.

[G8nightman]

Originally Posted by SAM/CH ZR-1

Hello Bob

Allowe me please to tell you something about brakes.
I understand when it's about a brake update, many ZR-1 owners don't want or can't afford to invest money in driving security. But keep certain facts in mind:

When you want a firmer pedal, with new stock or stainless braided hoses you won't get it. The reason is, especially due aging the caliper use to spread a bit more than new ones.

Some low-budget drivers suppose when they install a C5 upgrade it will become significant better, but it also isn't the case. The reason here is the C5 caliper pistons have a bigger diameter and also a bigger volume. The pedal can't become firmer due to a volume imbalance between the main brake cylinder and the caliper volume. Another point is, the C5 calipers also do spread a bit.

I have customers who did a C5 upgrade on their ZR-1 but soon changed back to stock because the result wasn't satisfying.

The solution is to go with 4 or 6 piston brakes when you consider a upgrade, and I am not talking about the C6 Z06 brakes because its piston volume is adjusted for the C5 and C6 brake system but not for the C4. These brakes are mainly good for a nice show behind big open rims.

Porsche recommend to go in high performing cars up to 500 hp at least with 4 piston brakes at the front and over 500 hp with 6 piston calipers. Additionaly a update at the rear can also be installed but that is something for those who race or have money to spend.

I wonder how people can spend alot of money in big cubic inch motor upgrades but don't care about a significant better stoping performance. In my opinion it's like a playing with the fire. Some guys believe they are experienced drivers and can handle with the very most traffic situations. But the unexptected is often unpredictable and it can depend in a emergency case on just some inches or feets. The stock brakes are good for 1-2 hard stops from 60-0 and that was it.

I do work together with the german brake manufacturer Mov'it (take a look at:http://www.movitcars.com/rahmen/corvette.htm) and we developped for the C4 a fit bolt on brake system for all 3 different stock 17 inch rim designs. You can install the 4 or 6 piston brakes without to have to replace the stock rims.

By the way: One of my clients run with sawblade rims and want to sell his black 4 caliper 322 x 32mm Porsche front brakes with about 4'500 miles on including all holders, screws and stainless braided hoses.
He is going to upgrade his brakes to 6 calipers at the front and 4 calipers at the rear for his new 427 engine.

If you or anybody else is interested in this kit, let me know.

Hi Sam

what is the 6 piston setup going for?

[mike100]

The C5 brakes are mounted on caliper slides and have a little bit more give and play resulting in a slightly less firm pedal. Although I have been in other C4's with J55's that weren't super great feeling- it does seem to vary from car to car.

You will have to spend more than a $1000 to do C5 brakes if you don't have the wheels already. I did mine only because I got a box of parts when I purchased the car. The rotors are cheaper (and thicker) plus you do get a lot more brake pad on the disc. My conclusion is not so much about the brakes, but the weak gain on the brake booster. Regular non ZR-1 C4's are especially weak feeling with only a single diaphragm booster.

[mike100]

of course don't forget to budget for a spare tire solution with big custom brakes.

[Bob Eyres]

Thanks a lot guys. this has been very instructive.

Though I'm the type that generally looks for an opportunity to upgrade, I think I'll stick with the stock setup.
Mostly for the impression that I get that the C5 upgrade will improve the car's ability to withstand repeated hard stops without fade, but would not give it that seriously shorter stopping power that I had wanted for the $$.

Also, Although I have A-Molds mounted now, I want the ability to go back to my perfect set of those beautiful original saw blades if I choose.

We're going with new stock type rotors, new brake lines and pads.

Thanks again.

[SAM/CH ZR-1]

Originally Posted by XfireZ51

Sam,

Would you explain further what you mean by the C6Z brake piston volume adjusted for C5-6 but not C4?
I have the C6Z brakes, front and rears and using stock master/booster. In the 2 years of driving I have not sensed any inadequacy from them. I first had just the fronts, then upgraded the rears last year including the eBrake. I don't track the car although I have hauled it down from 225km/h+ a few times with no drama. Having enough brake is the least of my concerns. Yes they do look nice behind 18"+ wheels. One of the reasons I did it was due to limited tire availability for 17s.

The brake systems of a C5 and C6 have the same piston volume. The C4 has another one.
The C5/C6 stock caliper pistons work with a 2 x 40.5 mm diameter, those from the C4 with 2 x 38 mm. The volume difference is about 14%.
When you install C5 brakes in a C4, the fluid volume ratio between the C4 main cylinder and the C5 calipers does not match. The consequence is the brake pedal become soft. With a Mov'it brake you have a hard pedal.

We wanted to open for C4 drivers the possibility to have a high performance brake without additional costs for the necessity to go with expensive 18 inch rims and tires. For the 17 inch stock rims exist the following brake upgrades:

Front:
322 x 32 mm with 4 pistons
342 x 32 mm with 4 pistons
342 x 32 mm with 6 pistons

Rear:
299 x 28 mm with 4 pistons and overtaking the stock C4 caliper for parking brake
342 x 28 mm with 4 pistons and a seperate small parking brake caliper

No spacers are required because the additional necessary offset is already in the 2 piece rotors implemented.

It also exist a 370 x 32 mm 4 and 6 piston upgrade but this set require 18 inch rims.

I don't want to say the C6 Z06 brake is bad but this system is just not calculated for the C4 and its about 400 lbs heavier car body. Running a C4 hard in the hills or a race track you will feel the difference between the Z06 and a Mov'it brake.

[XfireZ51]

Sam,

How does the difference in "swept area" play into this? You are looking at front/rear rotors that are 1" larger than the stock ZR-1 rotors. Again, I don't race the car, but my experience has been that the pressure needed to slow/stop the car is noticeably less than w the Brembos I had up front. I see that u have a 90 and it's my understanding that the master/booster for the 90 is smaller than what was used for subsequent years. Some have used Camaro master/booster for use w Wilwoods for example. In my 92, the master feels more than adequate in terms of pedal feel and travel in combination w the Z brakes.
Just to clarify for others following this thread, my beginning objective was to use the Z06 wheels for the aesthetics and tire availability. Originally the car came w Brembo fronts under A molds. When I switched to Z06 wheels, the front tires protruded past the front fender noticeably. Part of the issue was the extra thickness of the Brembo rotor hat. Swapping in the Z06 calipers allowed use of the Z06 rotors, which are heavier, but they also reduced the offset putting the outer edge of the front tire almost virtually in line with the edge of the front fender.
The 19s, on the other hand, made the 12" stock rotors and caliper look rather puny. I do use 18mm spacers on the rears for the proper wheel/fender alignment.

[nelson007]

Thanks Billy



[/B]QUOTE=Billy Mild;226004]http://www.amazon.com/Dupli-Color-BC.../dp/B000B6AF80

I used this, but got it from Advance Auto Parts.

I wanted to use the paint brush route as I feel the coverage was better. I did about 3-4 coats. Brake fluid will still ruin the finish so be careful.[/QUOTE]

[-=Jeff=-]

Bob, if anything you may want to consider finding C4 Grand Sport calipers, they are direct swap to yours but are a stronger caliper

[batchman]

Sam, you bring sound tech to the brake upgrade question but I have to take issue with this statement:

Originally Posted by SAM/CH ZR-1

The stock brakes are good for 1-2 hard stops from 60-0 and that was it.

My car does nothing but autocross, which is basically several 1 minute long emergencies (20 to 70 to 30 to 60mph repeat 10 times) with 5-15 minutes in between. While I have managed to boil my fluid on a couple of occasions, that's been a combo of fluid age and over-braking - the J55 setup is not really the limit there, if you have pads that can take some temperature. The tradeoff part of pads that *can* take some heat is dust.

The PBR caliper is certainly not the best in the world but it is far from the worst. You will see some pad taper owing to the caliper flexing, but you have to work 'em pretty hard to get there.

There are a lot of different configurations of C4 brakes, with varying pedal ratios, different master cylinder piston sizes, different caliper piston sizes etc. All of these things, along with rotor diameter, can be thought of as levers. More lever equals more work per input.

My personal battle with the 91's brakes are due to the smaller pedal ratio, the small master cylinder piston size, and I believe the inability to bleed the ABS unit. Bear in mind my prior autocross car was a 99 Cobra with very similar calipers/rotors but a MUCH larger master cylinder piston. Long pedal travel is not a great answer in my use of the car, but I can see how it would be very beneficial at 150mph!

Cheers,
- Jeff