stubby

Hello All....

To start, I have already done an advanced search on this question. I could not find the information I was looking for. Either I'm not using the right buzz words, or it's not covered. Probably the first reason.

Anyway, I have a 1992 C4, six speed with ABS. I upgraded to C5 front calipers and rotors, Hawk HPS pads and a DRM bias spring. We took it out to the track and had a racing instructor friend of mine take it out. The track we ran on is known for being quite hard on brakes. Well, it lasted 3 laps and the brakes were gone (big time fade).

I have ordered a set of Hawk Blue racing pads for it and am looking at adding an adjustable proportioning valve. After adding the DRM bias spring, I did not notice any appreciable braking shift to the rear of the car.

My question? Will an adjustable proportioning valve work with the factory master cylinder and ABS? Anyone that has done this, where did you plumb it in for the best results. If I'm barking up the wrong tree, I am certainly open to other ideas.

Thanks

MarkBychowski

I have a Wilwood bias valve on my '96, but it's not on the stock master cylinder. I have a modified MC from DRM with no internal bias spring (so the front and rear ports from the MC have the same pressure). The bias valve goes in-line on the rear brake line out of the MC.

The problem with putting one on the stock MC is that it already has an internal bias spring. I don't know how that would affect the operation of the external valve. There may be a way of running the stock one without the internal bias spring and just running the external valve.

My ABS functions perfectly with the valve.

Just curious: are you running the same pads all-around?

stubby

Hi Mark....

Thanks for the infomation.

I am running Hawk HP Plus on the front and HPS's on the rear. The guys I play with run a driving school and run full size stock cars. The pads I have now were a lets try to see how they worked for street and track. Street, fine. Track, not so fine. The car spends most of it's time on the street, but I want to use it for track days and driving school. I think I may have confused the car as well by going to 18 inch tires and wheels. The ABS doesn't seem to be working all that well. First full brake application with the C5 calipers and tire and wheel swap ended in a pair of brand new front tires being flat spotted. Also, after any hard brake applications, most of the lights on the drivers information center light up. (ABS, ASR, etc.)

What was involved with the change over on your master cylinder?

0Randy@DRM

Stubby,
I sent you a e-mail before I left work.

But in a nut shell. Fade? Pedal to the floor or hard pedal no stop???

Our spring alone or any other type of valve will not ever fix the 3 lap fade issue. Other things are causing your issue. Playing with rear bias can make the issue better, but no way going to keep the car stopping for more then 10 laps with your current setup.

Randy
PS Why the HPS on the rear anyways???

Tintin

I suspect that you need to use some cooling ducts for the heat problem you are dealing with. Brake systems convert kinetic energy into heat in a scientific sense and you are overwhelming the ability for the system to take on more work. Pushing brake bias to the rear will not increase the stopping power or the time that you go without fade because most of your stopping is in the front brakes at speed in any case.

Take the pads out and check for glazing. They will be shiny and smooth or perhaps pitted in the extreme.

Did you bed the pads before you went to the track? I'll guess that you did but if not - with new pads do 6 moderate stops in a row from about 50 mph. Let the car sit for 30 minutes. Do 6 progressively harder stops from 65 mph and let the car sit for two hours or so. The brakes will last longer and the pads will not easily glaze...

You might try the parts bin at GM and get a brake fluid cooler from the 9C1 Camaro - the cop car.. The rear drive Impalas had them too, but I think the same master in the C4 is in the 93-97 police pkg Z28.. Others will know better than I about fitment to your car. The cooler works, I used it in the Deathmobile, my ORR car...

Ducts are easy to make or install the pre made kit

ZR1 MK

You dont want the stock internal prop valve and an external adjustable too. You would reduce rear braking even further, and that not what you want. The external adjustable valve mounted in-car is highly recommended. You just need a master without an internal prop valve.
FYI, I took the stock master apart to eliminate the internal valve, but wasnt successful. I was told the old world challenge cars did this, but after much work, I think the info was wrong. I would like to hear from any c4 wc owners regarding that mod.

Slalom4me

Can you provide a little more information about the GM OEM (9C1)
brake fluid cooler?

I am familiar with brake fluid recirculators like the unit mfr'd by Dan
Press Industries (DPI). However, these need suitable calipers with
cross-over passages that can be plumbed to provide the return side
of the circulaion circuit, such as those made by Wilwood. I don't
know of a way to recirculate fluid with unmodified Camaro/Impala/Corvette
OEM calipers.

Is the BFC you have mentioned some form of heat shield to provide
insulation from the exhaust manifold?

Is there any possibility you are speaking about the Hydroboost-style of
brake booster, used in place of vacuum boosters on certain OEM truck
applications and also available from the aftermarket for non-stock apps?

While I think it is unlikely that the HB is what you mean, it is driven
by the power steering pump and there is typically a p/s cooler included
in the circuit.

I have a Hydratech unit for my C4.



Here is a photo of a Vanco unit for a Jeep application from Stu Olson's
Jeep Site



.
.

MarkBychowski

I got the M/C from HRocks when he was selling his car. He bought it from DRM and had it as a spare. I believe it's a modified Tahoe unit. It bolted right up in place of the stock unit.
With the lines, you'll need to fab up briaded stainless lines (-3 or -4) to connect the rear port to the external bias valve and back to the hard steel line. You'll also need to fab a line to connect the front. On mine, the ports were on the opposite side from the stock one. Fabbing the lines is pretty easy once you figure out which ends to get and route them properly. The biggest pain was connecting the braided stainless lines to the stock hard steel lines. You can either get the tools to re-flare them and get adaptors, or you can just get adaptors that convert the metric inverted flare ends to -an male fittings. I did the latter. Got the adaptors from Classic Tube. They were the only place on the planet where I could find them!

I ended up putting my bias valve in the engine compartment, but I'd strongly recommend doing what ZR1MK did and putting it within reach of the driver so you can adjust it without parking the car.

If you're interested in all the details, I'd be happy to send you pics and the specific parts.

Tintin

http://www.pfyc.com/store/merchant.m...ct_Code=GN4021

I can't find the original stuff I used, but these babies should do the same thing.. combined with cooling flow from ducts you will see a positive result

Slalom4me

Thanks,

Ken R.

.

stubby

ZR1 MK....

Thanks for the information. You answered the next question I was going to ask with respect to modifying the stock master. Which master did you use with your set up?

Randy.....

Also, thank you very much for your information. The car came with cooling ducts when I bought it, but I don't think they are of any quality. I am in the process of collecting the required pieces to rectify this issue. The rear pads are HPS's and the fronts are HP Plus. This is the suggested pairing I was given by the stock car guys. No one was really sure if it was going to be what I needed. I just spoke with the guy I had try the car on the track. There was a combination of hard pedal and then no pedal. Again, this track is known for being notoriously hard on brakes. Even the stock cars we run up here with Wilwood, Brembo and fancy recirculating master cylinder set ups blow off the track in corners because of the no brake issue. If I want to go to the adjustable bias valve in my car, what do you have to facilitate this change over. Apparently you have a modified master cylinder with no internal bias valve. As far as brake pads, we are getting a set of Hawk Blues that I will put in for track use only. Any suggestions.

Mark.....

If you could, I would greatly appreciate pictures and parts lists of your master and adjustable bias install. Thank you very much for the information you've already provided to me. Fortunately for me, you guys on the Forum are willing to provide this information to us Newbies. Saves us a pile of time and money. Again, thank you very much.

TinTin......

I appreciate your input as well. I am in the process of rectifying the ducting issue. I will keep the cooler set up in mind should I not be able to solve this problem with the other suggestions.

ZR1 MK

stubby
I use the DRM master supplied by DRM. Its a camaro unit, but I dont recall the bore size. Randy should know.
I just came back from vacation and got a ride in Mark Babbitts car at VIR. He hammered his brake quite a bit and I was impressed that he doesnt use a prop valve. He has the 1.25 bore truck master. Im still baffled about the absense of a prop valve. He posted a pic of his cylinder in another section a few weeks ago.

94ZR1#444

Stubby,

This is coming from my experience of 50 HPDE track events (no auto-x) over 3 years. I kick myself again and again for not doing this earlier. I kept detailed records of how much I spent on pads and rotors and this new setup from Randy will pay for itself after a year and I won't be changing pads after every event. Buy a Wilwood GNIII/ST setup (and move or mount new J55 calipers in the rear) from Randy. I'm using PFC01 pads. Install a 3/4 ton MC for $27 at NAPA. I already had the braided lines so the brake lines, which I thought were going to be the hardest part, were actually some of the easiest of the install. I have to thank ZR1 MK and Corvette55 for all of their help getting my car to where it is now. I was able to finally test my setup at VIR Mon/Tues with the NCM event. ZR1 MK was riding along. No proportioning valve was used. The brake pedal was high and very firm all during the session. I wasn't driving my car as hard as the new Z06 that I was driving, but the Rippie setup works GREAT.

Mark

stubby

94ZR1#444 and ZR1 MK

Thank you guys very much for the information you have provided. I am still working on this issue, and every bit of information helps. Thanks again, I really appreciated all the help you guys have been giving me.

Laszlo