Having a hard time going full throttle with braking. I'm really easing on the brakes to a 3/4th position, not fully depressed. When braking hard card seems to get very loose.

I'm also not certain that I'm feeling ABS come on. I have had the Ebrake light lit up on dash for a while but thought that was tied to Ebrake wire being disconnected or something.

Someone suggested it could have to do with toe (I think he said rear toe)

I'm running a front BBK with vents Ferrado pads front and back stock rear calipers..

 

I thought the brake light was directly related to the ebrake and master cylinder fluid level...

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I've had similar issues with a bad alignment. Under braking the car felt extremely unstable and the rear felt like it wanted to come around

 

I know what you are saying here, but they way it's worded it sounds like you are trying to brake and go wide open throttle simultaneously Maybe reword to "full braked pedal pressure"?

You are running an AP1 correct? If you haven't put on a rear bumpsteer kit on yet, I recommend it to tame the effect a bit. Either way, you are feeling an effect of the rear suspension geometry toe-out under extension. If you have been tracking the car for a while and pushing the brakes hard, but this issue has only developed recently, than I would definitely look at your rear alignment to make sure you have a sufficient amount of toe-in.

Once this is done, you might try adding some rear rebound. Under braking, this will slow weight transfer to the front of the car, but also, reduce the rate at which the rear wheels extend and toe out, stabilizing the car more (in theory anyway.)

RE: warning light, definitely check master cylinder fluid level to ensure filled to MAX line. If you have been eating through pads on track, it's easy for the fluid level to drop quickly.

 

...Or add some more spring rate and or compression damping up front to remove dive, keeping the rear of the car weighted. I would do this before adding rebound in the rear, that would be band aiding a side effect of the problem rather then possibly eliminating the problem to begin with.

 

I'd add: check front and rear bushings.

 

Run lesser compound in the rear pad.

 

What are your alignment specs?

What dampers and spring rates are you running?

What type of tire and what size(s)?

And we are all assuming this is occurring on a race track?

We need more info for us to help you

 

I'll second bushings as a likely culprit. When they start to get tired you'll get a lot of deflection under threshold braking. New bushings fixed this for me.

 

More rear toe and wing?