DonF

I ran at TMS this last week end and a brake problem that I have never had before came up.
First the only change that I did since the last auto x was to put Perfect Brakes EBC Bluestuff pads on the front. I have Hawk Hps on the back. I wanted to try the Perfect Brakes pads & they seemed to work great. These are on my 96 lT4
The prob I had on and off, not every time, is when I have to brake hard the ABS kicks in I can hear it and feel it but the power brake went away and I did have some manual brake, not good. This would happen on and off so I really didn't know what to expect on any run.
I change my fluid pretty often during the racing season so it is very clean.
I was told that the two diff. pads are confusing the computer???
Any in put out there? Thanks

naschmitz

If it was a C6 I'd say it was ICE MODE. If the ABS kicks in initially and then the computer decides you are on ice, it stops pulsing the front brakes and uses only the rear brakes to stop the car. The pedal goes hard and stops pulsing in ice mode. You either need to change pads or squeeze the brakes more gently rather than stabbing them.

Don't know if C5s had ice mode or not.

DonF

The 96 is a C4 & it doesn't have an Ice mode that I am aware of.

beerkat

You might have more brake grip than tire grip. It will make the ABS act up

Solofast

WRONG ANSWER...

C4's have had ice mode since the second gen abs systems were introduced (I think) in 1988 or 1989..

Could very well be ice mode if it happens when a wheel is unloaded you can get it easily in a C4. Worse if you have light weight wheels.

There's a funny story about disabling ice mode at the Cincinnati Pro Solo back in 1990, but you do what you have to do..

jaa1992

Brake pad torque is not balanced for your car.

On my 92 I run Carbotech XP12 on the front and XP10 on the rear.
I have a bias spring in the master.
If I run street compound its easy to get the ABS to kick on because the brakes overcome the grip of the tires real easy. Have to modulate the brakes a lot. With Hoosier R6 I can brake later and harder and still have to modulate the pedal a little.

I've never had the feeling of "shoot I lost the booster" hard manual brakes. I did replace master, booster and all 4 calipers last winter.

kimmer

Since changing my pads to Hawks, my brakes actually lock up when autoxing, It happens when I stand on them.

66IISS

Ha. have fun with it. We've been battling brake issues on our 96 LT4 for a whiile now.

The answer? Be gentle and brake in a straight line. The '96 ABS gets really upset when you try braking with the wheel turned a little bit. This problem is amplified when you "stab" the pedal. We haven't played around with different compounds on the rear, but I'm sure it's not happy with the compound you've currently got in the rear vs. the EBC in front. I know C5's got cranky with different brake compound combinations.

DonF

I had Hawks all around & couldn't really lock the brakes up unless I was running in a low speed auto x. A lot of drivers rave about Hawk pads though. I am trying EBC to see if I can get more stopping power at higher speeds.
Even when running stickey tires I didn't have this probplem though. I am wondering if I should take it to a dealer to power bleed, I am told that is the only way to insure that there is no air in the ABS.

DonF

Any other suggestions I'm all

Adam@Amp'dAutosport.com

I think you have a pad issue with 2 diffrent pad materials. Im not trying to sell you a new pad, but we see this issue all the time when you mix diffrent pad mfg's. Run againg put your old pads back on the front see what happens. If not we offer 7% discount forum on our products. Carbotech has all the high speed stoping power you need.

Solofast

I've just always used the stock pads with the stock braking system. On our BSP car we used pads that needed to be hot to work and always dragged the brakes to the line for the first runs. There was always some shift in bias as it got hotter and we had a protocol of how much we cranked the bake bias valve based on the surface and the number of runs we did. More work that it was worth and the car never really stopped any better than a stock class car.

Bottom line is that if you have J55 brakes on a C4 the stock pads work very well in autocross. Since you can overpower the brakes and get to lockup, the most important thing is getting the front to rear balance right, and the stock pads do that just fine. You can open a can of worms by messing with different pad friction coefficents, and while for track work it makes a big difference, for autocross, a pad more like a stock pad works just fine.

I know we all think we want more "bite" but if it activates the ice mode it didn't really help, did it? More important to autocross being able to get on the brakes hard, and then modulate the brakes near lockup and be able to apply them quickly without overdoing it and locking up as they are applied, as well as work well both cold and moderately hot. This is what stock pads are better at doing than high performance pads that are engineered to work at higher temperatures.

DonF

What kind of speeds do run at SCCA Auto X's? We get pretty fast in our Texas Low Speed Auto X's & stock breaks don't work well. I guess that I will wait for the back pads & see if that is my problem. Thanks

1991Z07

I use Performance Friction Carbon-Metallic pads on my '91...never had any issues like you are having.

I have to agree that there is some differences between the two compounds causing issues with your ABS. Cheapest thing to try first is buy a full set of STOCK pads and drive the car hard to see if it still does the same thing.

If it does, your issues lie elsewhere than the pads. If it still does behave like that, then there is something amiss in your ABS controller or the ABS pump behind the drivers seat.

Solofast

I've run the C4 stock pads at a lot of NCCC high speed events and never had any issues and I won NCCC convention (and took the Group II win also) in 94 at MIS on stock pads. One lap on a track isn't enough to fade the stock pads, in my experience. Maybe an issue if you run a bunch of runs back to back, but unless the brakes are hot to start with one lap isn't enough to heat them to the point where they stop working, assuming that you are using the GM stock pads, if you're using aftermarket no name replacement pads that's another thing....