blackrat

Was going to post this in brakes and suspension but figured I was more likely to find out if this was somewhat normal here.

Had a track event yesterday, my car has Hawk track pads front and rear with changed fluid and was stopping really well. Came into one turn hot and had to really get on the brakes, gradually went into full pedal in a straight line. ABS started pulsating like normal until I started getting some heavy chattering from the rear. Stayed on the brakes until the back end started sliding to the left at which point I released the brakes, corrected, and went into the turn with no drama.

Low Trac light went on immediately followed about a half minute later by the ABS inop and the BRAKE light. Continued my session going easier on the brakes and called it a day. The lights were gone when I next started the car but I'm wondering what the hell happened? I know after having my car dynoed the low trac and ABS inop light will come on if the front and rear wheel speed sensors are way out of sync but I don't think this is comparable. Could the fact the rear end went sideways while braking in a straight line mean something is up with my ABS? I've braked harder in far worse situations (heavily crowned roads, not in a straight line) and never had the rear slide out on me like that. I'm aware of how hard braking makes the rear light and prone to coming around but this didn't feel like that, it was more like something mechanical going wrong and all the warning lights coming on has me wondering.

athornt2

iTrader: (18)

Sounds like you had some wheel hop under braking. Our cars are some what notorious for that. I've had the exact same thing happen in my car... the lights stayed on until I turned the car off and re-fired it.

Mitch and some others here have a lot more experience with setups than I have, so I'll let them chime in and offer more accurate advice.

blackrat

Yes, it was definitely wheel hop. So all the lights started showing up for you as well, weird how it shuts down the ABS. I don't understand why it's set up like that.

As you said I'll wait for the others to hopefully explain why it happened. Like I mentioned it was a pretty straightforward manuever, I've braked much harder and more abruptly and in under worse circumstances and never had it act up like that. I'm running the stock full length torque arm as well, no shorty drag style.

pitbull14218

iTrader: (3)

Was traction control on? My car wheel hopped from launching on the street with nittos last night, it didn't wheel hop until 10mph when tires started to catch... but i don't think i got a low traction light. I used to get the light all the time on a 1-2 shift w/ street tires, like i said i have traction control turned off everytime i start my car now though.

blackrat

It was off. The low trac light comes on if the ABS starts working regardless of whether you have tracion control off or on though.

Arctic2002ss

Been there, done that. I was running(HPDE) at Texas World Speedway maybe 2 years ago and there is a big bump in 1 braking zone that I will brake heavy, back off over the bump, and then give it a little more brake before the corner. Apparently the ABS did not like one of my trips over that bump. I didn't think anything about it until the next big braking zone coming off the banking at 130+ and the rear kept wanting to step out under braking. WTH? This is new. Then I saw those same lights. I finished the session, which was a little more interesting without ABS. Once I got back to the pits and restarted the car, everything was fine and has been fine ever since. I think the sensors get all confused at some point and just stop working until they are reset.

athornt2

iTrader: (18)

Mine happened after really heavy breaking over a bump too. The bump is what caused the serious wheel hop for me and then the abs inop light came on... and stayed on.

blackrat

that's weird, I wonder why the rear end is so lively without ABS, or perhaps maybe only the rear ABS is disabled while the front are still modulating. I'm not sure how the ABS logic is set up. Having driven several cars without ABS I've rarely had the back end step out under braking without some action up front first unless the car was in a turn or you agitated it with a harsh downshift at the same time.

driver91

My 1999 Camaro without traction control will wheel hop when there is a reduction in grip either caused by grit on pavement or braking in a less than flat situation. Can be a pain as the car will swap ends if you do not lift off the brake.
Sometimes it helps rotate the car but it is hard to predict.

My setup is single adjustable Koni's, FeyII Watts Link, Heim joint adjustable LCA'S with lowering bracket, Hawk pads, slotted rotors, Adjustable tubular torque arm, 200 lb. springs, Strano sway bar

Koni tells me that they can revalve the shocks to help dampen the wheel hop.

I have not done it since I am selling the car.

I have a tendency to brake late and very hard. I am trying to overcome the tendency since my co-driver brakes sooner and softer and is faster than me.

I have no wheel hop issues accelerating. 400RWHP/400RWT, 3:73, TorsenT2R

I was able to reduce the braking wheel hop by going to 800 lb. front springs which reduced the tendency to unload the rear end. 200 lb. rear springs also helped.

The bad thing about wheel hop is it is not predictable.

I would talk to your shock supplier about valving.

Hope this helps.

waxenate

iTrader: (5)

help! Traction light stays on after key is removed! WTF? lol just swapped a 2000 ls1 into a 95 z-s8 without trac control.....any ideas?

2000Z28M6

iTrader: (13)

I've been having constant issues with the ABS system under harsh conditions mentioned. It seems to reset with a simple restart, but it really blows that it will happen in the middle of a session.

Anyone know of a fix? Or is it just time to bypass it and go NO ABS?

I didn't realize how sensitive my pedal is now and it's hard to re learn how to brake with so much stopping power...ie lock up the fronts too easily.

SIK02SS

iTrader: (11)

edit- didn't read the thread

SIK02SS

iTrader: (11)

Brake bias plays a huge role in why the rear end snaps around under braking. If bias is too far rear, under hard braking the rear end wants to come around. Even without a modulation on bias, you can adjust your brake bias via pad compound.

SIK02SS

iTrader: (11)

what suspension mods?

BenZ28

I'm having the same issues as described above for a couple of years. The ABS is deactivated and can only be reactivated by shutting down and restarting the car. Having no ABS wouldn't be a problem for me but unfortunately the rear brakes just lock too soon to continue the session and brake later as usual...

2000Z28M6

iTrader: (13)

You should check the BCM it can go bad and it controls ABS.

It fixed my issue!

BenZ28

What exactly did you do? Did you get a new BCM?

2000Z28M6

iTrader: (13)

Search ls1tech there was a thread that mentioned replacing it or you take it apart and resolder the pins on the board.

It just gets old and the solder cracks and causes all sorts of electrical gremlins..this damn thing controls your radio, windows, abs and a few other things.

Joseph Freda

Real drivers don't need ABS

wrencher

iTrader: (2)

Most that HPDE F-bodies just run a decent stock rear pad to keep wheel hop tendencies down.
The ABS is controlled by the EBCM or EBTCM ( electronic brake/traction control module)

There is no tuning or adjustments you can make to the EBCM.

As mentioned above the module will get to a point where it thinks it cannot trust the wheel speed sensor signals.
It's a plausability judgement in the EBCM's programming.
Definately set up for street driving, not performance.