MarkBychowski

Hi all,
For background, my car is 90% street, 10% track. For brakes, I currently have
Front:
GS calipers with shortened SS pistons, 1.25"x13" rotors/aluminum hats
Rear:
Stock calipers/rotors
PFC Z pads for street use, PFC race pads (01/97) for track

I Recently picked up DRM's Wilwood 6-piston kit for the front (used). I'm now struggling with what to do with the rears. I can think of a couple options:
1) Leave stock. I worry about this option since that will give such a strong front bias. Can be mostly corrected with a bias valve, but I'm not sure?
2) Move my current fronts to the rear. This was my initial plan, but found out that the brackets are about $750.

I'm fine with spending $750 (although it seems high for a set of brackets), but was wondering you guys had any better suggestions.

Thanks!

John Shiels

I am not the most sensible person with money but 750 for two brackets is Try it with stock rears you can always change it later.

L98 DRIVER

Try the stockers on the rear first
and also DRM has a BrakeBias Spring they claim will change the bias from 10% rear to 15% rear and at $15 or so its worth a try

MarkBychowski

Thanks guys! Looks like I'll give it a shot with the stock rears and see how it balances out.

STEVEN13

Hi,

I run stock calibers with SS lines PFC 01/97 also with the DR spring. I have no problems and it stops good.

Steven

DREGSZ

Melrose T Tops has the mount brackets to put the PBR/LT1 front caliper on the rear for under $400 but try it first, the 6 pot wilwoods will only increase the front brake efficiency by 25 % over the C5 front calipers on the C4, ( I don't know haw much better then stock PBRs that is)

Try stock first anyway, you don't want to make too many changes at one time better to try one thing before adding the next modso you can figure out what causes what

BrianCunningham

Hey Mark! How's it going?

Just to add, the kit from Doug Rippee that mounts the stock fronts on the back also comes with an option to mount small non-pnuematic brakes on the rear so you still have a parking brake. Which is needed in some stated so pass inspection.

2manyfuncars

I have GN-III's on the front and the stock calipers on the back. I adjusted the bias with a dual master cylinder balance bar set-up. Do the calculation based on piston areas and rotor radius to see where you need to be. The stock rears work OK on the track at first, but you can get some rear fade after some hard laps. Part of the issue is a lack of cooling and the thinner rear disc. If you put some ducting in to the rear you might be OK. It's not too bad, but still noticeable. The pads with good compounds are also expensive compared to superlites based on swept area and volume of the pad.

Good luck

MarkBychowski

Thanks very much, guys! I'll definitely check out the Melrose brackets and run some more calculations.

Hi Brian -- good to hear from you! Hope everything's well out on the east coast!

speedjohnson

I've also tried the GNIII's up front and the stock front's in the rear. It's a realatively cheap compromise (450.00 I think is what I paid for the adapters). It allows the use of larger pads which last longer. The rotors are larger (you can get the 1 1/8 thick 13's).

However, it is difficult when you start messing with the brake bias...it's harder than you might think to get it right. You have to take into consideration the larger rear piston diameter and the larger radial swept area of the pad in your calculations. And all this for a single piston caliper...with no option for an e-brake.

Depending on the size of your fronts, you might be able to get away with an in-line bias valve in the rears...as long as you don't have ABS, or, you can opt for the dual master cyld set up if you really want to pull your hair out. I tried this...and I am now bald.

MarkBychowski

I'll definitely avoid the dual master setup then! I do have ABS and defeintely don't want to lose it. I'm planning on starting with the stock MC and add a valve. According to DRM, it will work, but you end up with a low pedel due to the significant increase in fluid displacement. If it's bad, I'll step up to a larger MC. Gotta do these things in small steps so the wife forgets how much I'm spending in total

Do you happen to recall where you got your brackets? I still need to call Melrose and ask about theirs -- they didn't have much info on their website.
Thanks!

DREGSZ

You would have to ask for Dave at Melrose when you call.
You could also call Daryl at precision brakes 866-99BRAKE
They're prices are really reasonable for custom mount brackets
And they do work with PBR rear kits

I didn't know that putting a brake proportioning valve in will hurt the ABS.

Remember, the prop valve only allows you to dial out the rears by reducing fluid to them, you can't add to the fronts like in dual MCs

silver84

.
From the factory, what is the front/rear braking
percentage?
10% does not seem correct.
Also, does anyone know the caliper piston diameters,
for an early C4, from the factory?

DREGSZ

You should also call Daryl at precision brakes 866-99BRAKE
I spoke w Daryl today about my brakes, (Which fit great and look awesome!!)

Precision Brakes does these LT1/PBR front to rear caliper swap brackets for about $300 which is way cheaper then anyone else.
They also have other rear caliper options available.
You can discuss all that when you talk to Daryl.

Evan

mvitacco

Mark;

Did you get the Master Cylinder to go with the 6 piston calipers?
Darrell at Precision brake supplied a GM truck unit with 1 1/16"
bore and no built in proportioning as the stock M/S has. I'm
using the GNIII caliper.

Contact Kevin Hill me make me a set of cailper brackets that allow
the stock caliper with 14" Coleman rotors & Wilwood hats that he
did for his car. The stock rear brakes are not so bad, the problem
is that they need more proportining. Install a proportioning valve
first, you may forget about an upgrade as I have.

I did not have any problems setting brakes bias and I leave ABS on
all the time. I started with one turn out and keep going up in 1/2
segments until the back of the car got twitchy under braking,
backed of 1/2 turn and that was it. With the rear brakes actually
working, the car seems to stop noticeably better. Turn 1 on
VIR-South Course is a good place to set up brakes,as there is a
run off road avaiable (which I did not have to use) as well
as the fish hook (lower speed) turn.

MarkBychowski

I ended up buying brackets to put the stock PBR's on the rear. I talked with DRM (they're very familiar with the setup since they sell it also) and they said the stock MC will work, but with a low pedal. He suggested trying it out with the stock MC to see how I like it. If I'm not happy with the feel, my next step will be to pick up the modified truck MC and separate bais valve.

Right now, I have the entire suspension off the car. I'm doing new bushings since I had to take most of it apart anyway to do the brakes. With any luck it will be back together in plenty of time for an April event at Road America!

Thanks again, everyone, for the help!