Rear brakes locking up at the track

[DTFE30]

Agreed.
Any braking problems that coincided with any suspension changes should first be looked at as suspension tuning issues not really "brake" issues.

Sways should not really play into it unless you are only experiencing it under trail braking.

If you've been having the issue since moving to GC coilovers, perhaps you need to turn your rear rebound damping down.

Ok, thanks for all of the input guys. I will try that next time out and see if it helps.

[JimmyP]

Agreed.
Any braking problems that coincided with any suspension changes should first be looked at as suspension tuning issues not really "brake" issues.

Sways should not really play into it unless you are only experiencing it under trail braking.

[varg]

If you've been having the issue since moving to GC coilovers, perhaps you need to turn your rear rebound damping down.

[DTFE30]

Couple questions:

Do you have the rear bias valve in or out?
If its in,,, maybe its malfunctioning, sticking, clogged or otherwise just not doing what it supposed to.
I have had my bias reduction valve out for about 15 or more years.
When I had stock brakes on my E30 M3 I don't think I ever remember locking rears in the dry without the bias valve and thats with same pads F&R. There was enough bias built into the stock system that I never worried about rear lockup.

I don't know the friction characteristics of the pads you use so I cannot comment on that.

Do you think you are transferring too much weight under braking and unloading the rears?
Stiffer front springs needed or more compression dampening front possibly?

Do you think you may be going too aggressively to brakes?
Stomping instead of squeezing?

Biggest question -- Has anything changed on the car or did it always do this?


Just some food for thought.

Interesting. I'm trying to remember, but I think I have been having this issue since I switched to Ground Control coilovers. The spring rates are nearly the same as the brand I had before though. My sway bars are pretty small front and rear. they are eibach adjustable but I belive they are stock diameter when I measured. I run MAXXIS Victra RC-1s on it. I have never messed with the brake bias valve. I have to take a look and see if its even in there. I have had this problem in turn one of Palmer that is uphill and to the left, Turn 1 at Thompson that is flat and to the right, and now turn 5 a flat left at Pocono north. These are all high speed braking zones. Maybe I am getting on them too hard and not "squeezing on". I am definitely driving faster each time out, so maybe I have just been getting too aggressive with her.

[JimmyP]

Couple questions:

Do you have the rear bias valve in or out?
If its in,,, maybe its malfunctioning, sticking, clogged or otherwise just not doing what it supposed to.
I have had my bias reduction valve out for about 15 or more years.
When I had stock brakes on my E30 M3 I don't think I ever remember locking rears in the dry without the bias valve and thats with same pads F&R. There was enough bias built into the stock system that I never worried about rear lockup.

I don't know the friction characteristics of the pads you use so I cannot comment on that.

Do you think you are transferring too much weight under braking and unloading the rears?
Stiffer front springs needed or more compression dampening front possibly?

Do you think you may be going too aggressively to brakes?
Stomping instead of squeezing?

Biggest question -- Has anything changed on the car or did it always do this?


Just some food for thought.

[jlevie]

It could be that the 750msater cylinder isn't compatible with the rear brake bias valve, causing too aggressive rear brakes.

[DTFE30]

Hey guys. I've been having an issue with my rear brakes locking up at the track. I feel like I can't get on them they way I should. I think this might be due to the fronts fading and the rears making up for it. With quick firm application the rpms drop to abt 1800 and it feels like its not stopping, similar to sliding into a corner on a dirtbike with the rear locked up. A friend behind me at the track confirmed it was the rear locking. Right now I really have to squeeze on the brakes gently and its backing up my braking zones. Current setup:


- Stoptech Stainless lines all around
- cryo treated front blanks and regular rear
- PFC08 front and rear approx. 40%life left
- ATE calipers and brass guide pin bushings all around
- Cooling run from ducts to adaptor plates via Harrison motorsports kit
- Motul 660 fluid
- E32 booster and 750 MC


Any Idea what's causing this? Thanks in advance for any advice.