Brake Bias....
 

Ok, so at the last autocross I noticed that when I'm threashold braking the tail wanted to get a bit squirly. One possible reason for this could be the brake bias. (among other things, such as alignment ect...)

I'm thinking that I have too much brake bias on the rear, causing the rear end to want to lock up before the front, which makes the rear end unstable.
Right now I'm running Porterfield R4S pads and shoes. So I'm thinking of going to a less grippy shoe to help stabilize the car under heavy braking.

any other Ideas?

Couldn't you just toss in one of those Golden Eagle brake bias controller thingies and adjust it for track days?

^^ its not legal for the class I run in STS (Autocross)

You don't want to hear this... but put more weight in the back. Leave the spare in, fill the tank,etc..... give it some more downward push to keep the wheels spinning. That'll give the brakes some more mass to slow down, lessening the chance they'll lock on you. Another option may be taking out some air from the tires, but then that starts screwing with the handling too.
Less grippy shoes may be the best option, although I don't know what runs between porterfields and OEM. I'm still running OEMs with the Axxis pads in the front, I don't think I've ever felt squirlyness under breaking (not sure exactly what I'm looking for on that), but they seem to stop the car. I was under the impression the majority of the braking was handled by the fronts.

They do, but the problem is that the stikier the tires, the harder you can brake... which in turn forces more weight on to the nose of the car, making the rears have less traction meaning that they are more likely to lock up.

So esentially, when you get better tires, you actually want LESS braking power on the rear end...


And I'm not 100% sure it is a brake bias problem, as the ABS wasnt going off. It may have been just me causing it, by making slight course carections while under heavy braking. :shrug: