I have now gotten a few track days under my belt, in my E36 M3, and I have noticed that my brakes pulse/vibrate badly once they get really hot under hard braking. At the beginning of a session, no problem, but near the end when the brakes get hot, when I brake hard into a corner I get bad brake pulsing. When I first noticed it, I just assumed I had warped rotors that needed replacing. But then I realized, that I do not have this issue AT ALL when driving on the street. And even at the beginning of a track lap session, the brakes are fine, it is only after about 15 minutes on the track that I get the brake pulsing.
Any thoughts? Do I just need to replace the rotors, or is this normal? Or somethint else is going on here? Thanks!
You don’t mention what pads you are using, but it sounds as though the pads/rotors have overheated.
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Not normal. It is odd that it takes 15 minutes. But, my BET is that it's a combination of pad type and uneven pad deposits. A few fast laps gets you a good deposit on the rotors, then some combination of slow laps and minimal braking, or pulling into pits, holding brakes on while sitting still, etc, creates 'snarf' on the rotors, which will absolutely create the problem you've described.
Warped (or out of spec) rotors are VERY rare, and would cause vibration at all times.
What pads are you using?
Change to a different pad compound or brake harder to push past the uneven deposits on the rotors.
Inspect for a crack as well
Yes, what brand and model of pad would help diagnose the problem.
It's possible if your using a street pad, it could be depositing material on the rotor when you over heat them. Only noticeable under heavy braking when hot.
Pads are EBC Yellowstuff. I have not noted any cracks on the rotors when I self tech.
Last edited by skyotee; 12-31-2017 at 12:07 AM.
Do you feel the pulsing/vibration through the steering wheel and pedal?
It sounds like pad deposits to me.
When I first started tracking my car I struggled with brake shudder that would begin halfway through sessions.
I had a set of street pads and a set of track pads (PFC 06) and would swap pads before heading to the track.
After dealing with the shudder for a few events I bought a dedicated set of rotors that I would only use with my track pads.
The shudder hasn't returned once I stopped using street and track pads on the same set of rotors.
about 5 years ago at VIR I got a brake vibration that felt exactly like a warped rotor/pad deposit but it was neither..… turned out to be a bent hub.
I would try PFC.
They have an enduro compound (Usually even numbered) that will be usable on the street and does not require bedding once you get to the track. Once you try it you will not go back. There is a reason they are expensive... They work.
I was having this exact issue with my E36 M3 as well. I recommend upgrading to a more track friendly pad. Your pads might be reaching their heat limit near the 12-15 minute mark during your sessions.
- Max
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