Hello,

I don't know if this the correct section for this so please move if necessary.

Anyways, I noticed last weekend during a track lap day on my MINI S that when your foot is on the accelerator and you are trying to brake at the same time (trailbraking) that the brake fades very quick. It only happens after you press the brakes (while your foot is on the accelerator) a couple of times. It almost seems like the master cylinder is briefly disabled while you have your foot on the pedal. As soon as I took my foot off the accelerator, the brakes worked with full force again. Anyone ever encounter this? It seems to me that it was desinged this way but I have no idea why. I know it is a rare situation to ever encounter on the public road but I think it can become a safety issue if you gas pedal becomes stuck for whatever reason. Any input is appreciated.. If you don't know what I mean go try it on a street going at 30 mph. Have your foot on the gas pedal and pump the brakes a few times and you'll notice what I'm describing.

I have an 06' MINI COOPER S 6-speed with 6K miles.

 

yeh, it only made it look like i suck at driving manuals.

 

Probably a dumb point but.....you did have the DSC and stuff all turned off right? (sorry I don't know the correct terms, we don't have our MINI yet)

But seeing as how we plan to autocross it and I left foot brake quite a bit....this has me a little concerned.

 

Trailbraking is actually something different than what you are describing. It means entering a corner while carrying the brakes past the brake zone into the corner. This helps to rotate "some" cars toward the apex.

In what situation would you be applying both brake and throttle? Mid turn to kill understeer is all I can think of.

Since the booster is a vacuum booster, it may be seeing more vacuum than it would when you have your foot off the accelerator causing more boost to be generated. I have felt something similar in my old Camaro, it has a lumpy cam which does not provide much vacuum to the brakes. When idling, it has a hard pedal, but give it some gas and the brake pedal is easier to push. This is just an inference on my part, but it seems logical to me.