Steering Wheel shudders under hard braking

[fastcat99]

At a recent track event, I experienced significant steering wheel shudder under hard braking after the brakes heated up. No issues at all on the street or during early laps with brakes cool. Any thoughts as to what I should investigate here? I am running stock brakes with Dali track pads and fresh Wilwood 570 fluid.

 

[Ponyboy]

Uneven pad material transfer very likely. Did you put the emergency brake on in the paddock? With a hot brake pad, putting the emergency brake on will cause that uneven material transfer. Either that or you may have used a bit of extra brake while entering the pits from a session. In addition, sometimes in the pit area, you'll want to move the car a foot, forward or rearward, to let the part of the rotor that the caliper is covering cool.

You may want to take some fine grain sandpaper and lightly sand both sides of the rotor or have a professonal turn them.

 

[nsxtasy]

The reason for the shudder is described on Stoptech's website here. As Shawn notes, it is due to uneven brake pad deposits on the surface of your rotors. It will go away if you replace the rotors. Turning the rotors will probably make it go away, too, but it could return sooner than if you replace them. You could try sanding the surface of the rotors, as Shawn suggests. Don't forget to bed your pads after you replace/turn/sand your rotors. And any time you replace your brake pads, bed them according to the procedure noted with the pad or in the Stoptech white paper.

In every case I've found that the shudder occurs with the front rotors, and has nothing to do with the rear rotors. Since the parking brake only affects the rear rotors, I can only conclude that it is unlikely that the parking brake caused this problem. Still, it is good advice not to use the parking brake at the track, and to try to let your brakes cool down when you come into the pits, either by moving the car back and forth, or by driving around the paddock for ~5 minutes without braking.

 

[fastcat99]

Thanks for the info, folks. I suspected front brake pad material transfer, but didn't know for sure. It's definitely the front brakes (steering wheel jumps around).

For the record, I knew to never use the parking brake at the track and I do religiously move the car a couple feet back & forth as the car cools down.

I'll check rotor tunout and turn them, or replace if they are too worn. I need fresh pads, anyway, so the timing is good.


Thanks again!