Ron G

After running my 6th autocross this weekend, I think I have discovered what my problems are with my brakes (which get very hard to push - different than ABS) going into a turn-around after being on full throttle.

We think that being at full throttle, and then braking hard immediately does not allow the brake vacuum boost time to build up, causing a loss of brake power. Does this sound reasonable to anybody?

I'm guessing the only thing to do is to slow down the reaction - definitely makes left foot braking harder to do.

I didn't notice this on my 180FWD, but the 225Q is experiencing it every weekend.

nicetts

it up by left footing to get the boost up off the corner. Bastards! These systems just make the car slower most of the time. I can't stand the throttle games it plays either, but I guess I have to live with it for now. Something to be said for a NA, cable throttle engine w/ light components.

juliem

even if you do drive harder

How do we explain Joe's car NOT doing that on the same course? More polite driving since you weren't driving your own car?

Mine doesn't do it every time either... and I started really standing on it and was able, after that, to get the ABS to trigger. Guess my point is that I don't think it has anything to do with the calipers...

GWR

I have had that problem since my first autocross in my car, a 2001 225hp quattro. I have tried multiple things to try to overcome this problem: multiple check valves, bigger vacuum hose, a second canister, and finially a electric vacuum pump in series with the engine.

I brought this problem up on this forum last April, and is deteriorated to a driving style debate. The problem is very real, and if you drive the car at 10/10ths at an autocross, I can pretty much guarantee that you will have the brake pedal go rock hard on you. It typcially happens after a full throttle, slight brake, full throttle, heavy brake section. In the heavy brake section, the pedal will be hard and you won't have very little braking power.

I have done a lot of research on this problem, and with the electric pump, I have pretty much eliminated it, though the pedal feel is still inconsistent. If you want more details, send me an e-mail.

-Gary

GWR

unplugging the brake control switch at the top of the brake pedal. You won't have brake lights, but on an autocross course that shouldn't matter.

-Gary

Ron G

from accel to brake pedals, but of course, that will slow down the times (part of the reason I was off the other BStock guys by more than 1 second).

juliem

slow is no fun