try a less agressive pad in the rear....


maby during the weight tranfer of the initial hit of the brakes... your rear is getting a lil lock up... abs kiking on one side then the other... makign it squirm

 

It also could be a slight caliper sticking on one side. Take your rear wheels off and see if both left and right pads have the same amount of wear. If one side is sticking slightly, it will have a lot more wear...simple check in the box there.

 

I run 40psi hot at all four corners but with the advans I don't notice much difference between 50, 40, or 30.

 

Carbotech XP10 in the front
OEM pads in the rear
Hankook RS-2 or Advan A046
OEM alignment
OEM suspension
NO SQUIRM

Carbotech XP10 in the front
Endless Vita Nuova? in the rear
Hankook RS-2
0 toe front
1/10 deg toe-in rear
OEM suspension
NO SQUIRM

-Jon

 

Jeff,

You might want to consider a bit of a bias in tire pressures, too. I have run 44 F and 41 R hot pressures, or there about, but maintinaing about a 3 psi split between F and R. The softer rear tires will give a bit more bite when compared to the fronts.

I have run other cars that have a cockpit adjustable brake bias control. It allows you to adjust F to R brake bias on the fly. If the tires and brakes are fully warmed up, and you were to get the "wiggles " from the rear end under braking, you would adjust some of the bias from the rears and move it to the fronts with that adjuster. Your plan of using the Porterfield R4S pads (or another pad with less torque) on the Rear will accomplish the same thing, but without the need for an adjuster. With the right combination of pads fitted to the car, the stock brakes are very well set up in my opinion.

'Rat

 

Thanks for the tips fellas.

 

Well just got back from the lapping day at Grattan.... (Great Track - www.grattanraceway.com) .... and I managed to evade the brake squirm issue.

I ran 8 - 20 minute sessions and was hitting speeds of 125mph on the straight. Cold the smoking hot I didn't have any wiggle at all.

For the lapping day I ran XP12 fronts and Porterfield R4S pads in the rear. The car felt perfectly balanced all day nice and straight with plenty of stopping power.

I didn't try the XP10 rear pads at all. Maybe when I go to another track that isn't as much fun as Grattan then I will do a little more testing but yesterday I simply didn't want to waste kick **** track time on brake tuning especially since the car felt the best it ever had.

I'll keep this thread updated.