Hi all,

My hope is to pull some knowledge off this experienced bunch. This problem is killing me...

I came off an autocross this pass weekend and had a few scary moments. At the end of a "straight away" when I would transition off the gas and onto the brake, the ABS would invoke immediately, which in net effect, reduces the braking power drastically. Fortuantely, I just ran wide and didn't hit anything...

My thought on this is the ABS is envoking because I am jumping on the brake abruptly on what could be on slightly uneven surface while crossed up on the throttle. The wheels sensors figure I need anti-lock, and the system starts pulsing away.

I started changing the way I applied the brake and it reduced it a bit, but it wasn't optimal. Also, it didn't completely solve the problem as the ABS still came in about 4 times in 6 runs.

I'm running 265 width MPSC tires on 19s up front and 345s on the rear. The overal diameter is larger than stock which made me start thinking about if that is messing with the PASM. Has anyone experienced this before?

For the short term, does anyone know how to disengage ABS by pulling a fuse or what not?

Thanks in advance.

 

Are you sure it was ABS and not the notorious "ice mode" ?. Overall diameter should not matter that much as long as the difference between the front and rear is not significantly different than what the stock ones are. If I remember correctly, you should be within 4%. My car goes to Icemode frequently if surface is rough/bumpy and I'm too abrupt on the brake. If I set the brake/suspension smoothly, and then squeeze hard, it rarely happens. Also, next time you go out, set the suspension to soft and see if that helps. At our local track (Sebring) it definitely helps to have soft suspension.

 

How would I know if I was in ice mode?

I've tried the softer settings and it's slower than using the other option and going easy on initial braking... Which means to me-not a viable option!

My car is bone stock so I'm under prepared for the class. I'm going to need any edge I can get!!

 

With Ice Mode you pedal gets really hard, on high/top end of the compression, and car barely brakes. You can usually eleviate this by lifting just a little and then re compressing the pedal. I avoid it by setting the suspension before I go full force on the brakes. It usually happens to me if I wait until the last one 100's of a second and am forced to "slam" on the brakes in a bumpy area.
Common causes for Ice Mode are different diameter tires, very sticky tires (Hoosier R6 or slicks), bumpy tracks, abrupt application of brakes.

 

Thanks for the explanation. I have experienced that as well. Its frightening!

Has anyone tried disabling the ABS? I would prefer to change the car before having to change the nut behind the wheel.

 

It does sound like you might be getting interference from ice-mode. Like ErikG says, the pedal becomes hard and unresponsive. It's the car taking over when it senses difference in grip level and wheel speed. A friend, (experienced and fast) had it happen to him at a very fast section of track and wrote off the car after a big rearward impact with the loss of braking.

Try adjusting your technique by braking with less initial pressure. If you're jumping hard on the pedal, especially with side load in the car you could be inducing it without realizing it. I'm not sure if there's a way to tell if ice-mode has been engaged (dash light? thrown code?) but it might help to put a camera in there next time and see if you can catch it on video. Would be helpful to see what it looks like as it happens.

Another thing you could try is a less aggressive pad compound.

 

Thanks for the comments John. I believe I'm still on stock pads which has quite a bit of intial bite. Anyone know which pad has a low initial bite characteristic and suitable for autox?

 

Pagid Blues or Blacks would be a good pad without too much bite that will last and give solid auto-x performance.