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      11-17-2020, 12:02 PM   #1
richard in NC
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Brake Shudder

Does anyone else experience what feels like brake shudder when threshold braking on track? Seems to happen when slowing from triple digit speeds. It's been the same since my first track day with the car through my latest.
It may not be the rear brakes but its felt in the seat of the pants, not the steering wheel or elsewhere. If I ease into the brake or brake a little lighter it doesn't occur.

A friend said he felt it in his M2C.

Some have suggested its the rear toe changes as the rear gets lighter, others the rear brake bias.

Thoughts?
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      11-17-2020, 12:26 PM   #2
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I’ve never gotten it in my OG M2. I know it doesn’t help. As for thoughts, first thing that came to mind was #neverlift

Last edited by 5.M0NSTER; 11-17-2020 at 12:31 PM..
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      11-17-2020, 12:37 PM   #3
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Quote:
Originally Posted by 5.M0NSTER View Post
I’ve never gotten it in my OG M2. I know it doesn’t help. As for thoughts, first thing that came to mind was #neverlift
We actually had an exercise, trying not to use the brakes the entire session. I got up to good speeds allowing downshifts and tire scrubbing to slow me down. No brake shudder then

We also had a session in the rain. Less brake effort meant no shudder. The last 2 sessions I learned to ease into the brake, reducing the feel of it.

Check out exactly 1:00 into this video, you can hear the GoPro mount vibrate from the shudder. https://vimeo.com/476870974
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      11-17-2020, 01:21 PM   #4
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Quote:
Originally Posted by richard in NC View Post
Does anyone else experience what feels like brake shudder when threshold braking on track? Seems to happen when slowing from triple digit speeds. It's been the same since my first track day with the car through my latest.
It may not be the rear brakes but its felt in the seat of the pants, not the steering wheel or elsewhere. If I ease into the brake or brake a little lighter it doesn't occur.

A friend said he felt it in his M2C.

Some have suggested its the rear toe changes as the rear gets lighter, others the rear brake bias.

Thoughts?
How new/old are the pads and rotors? Brake shudder is very common, at least in my and fellow TD junkie's experience, and can be caused by an assortment of things. If you feel it in the steering wheel, it's the fronts, which are anyways the most likely culprit.

1. Being on the brakes while sitting in the paddock after coming off from a hot session and burning brake pad material onto the rotor
2. Bad bearings (not likely)
3. Cracked pads
4. Not properly bedding in new pads with different material than previous pads
5. Changing pads, using old rotors. In my experience, I could comfortably get through a second set of front pads on old rotors, but by the time I get to the third set, the surfaces are just too different and the effect is severe judder

I've experienced all of the above with the exception of 1, because I know better, and 2.

My suggestions would be to first take a look at the pads and make sure you have more than a backing plate's worth of material and that there are no cracks. A cracked pad would be obvious. If all good, then likely the problem will eventually work itself out given enough time. I've had judder so severe on new pads before that it felt like the wheel was going to fall off. I actually had to check to make sure I didn't put them in with the backing plates facing the rotor. Just really hammer on the brakes for every corner, every session. I know you say you are threshold breaking, and I don't mean to question whether you are, but really get on them to where there is a slight lookup. Do this for a couple of track days and it should go away.

Also, if you run with any of the nannies on, not sure how this can affects the brake feel.
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      11-17-2020, 01:58 PM   #5
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Quote:
Originally Posted by richard in NC View Post
We actually had an exercise, trying not to use the brakes the entire session. I got up to good speeds allowing downshifts and tire scrubbing to slow me down. No brake shudder then

We also had a session in the rain. Less brake effort meant no shudder. The last 2 sessions I learned to ease into the brake, reducing the feel of it.

Check out exactly 1:00 into this video, you can hear the GoPro mount vibrate from the shudder. https://vimeo.com/476870974
I did watch the video now, it notice it, but it doesn't seem too bad. The camera shakes even when you're accelerating down the straights.

It does feel like brake shudder. What pads are you using?

I got a steering wheel shudder with Carbotech/GLock pads before on my Mustang. Felt like a low frequency vibration, but I mostly felt it in my steering wheel.
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      11-17-2020, 02:16 PM   #6
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Thanks for the replies so far.
It's stock pads and sufficient depth per the track inspections. Last fall they were near new with < 6k miles. I recall doing a light bedding in drive after returning from track last fall but each track day has felt the same, no better no worse although a good bedding in exercise wouldn't hurt.

It will probably be spring before my next event so I may look into fresh track pads before then.....

PS: Yes I've gotten on the brakes hard enough to activate ABS at times on track, mostly when miss judging the braking point for a given speed.

PS: Even though I termed it brake shudder, I've had that before and this doesn't feel the same. More like the car is hopping on bad pavement but it's consistent in any high speed braking zone. I have few places to experience it on the street... maybe a nearby off ramp. But officer, I was only doing 100 mph to test the brakes.
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      11-19-2020, 12:45 AM   #7
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Had a massive issue due to warped stock rotors which feels like doesnt handle heat as well as some aftermarket rotors. Went to the exquis kit and never had the issue again.

This was for m2c with the original blue brakes not the new one.
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Last edited by kvnchu; 11-19-2020 at 12:51 AM.. Reason: added information
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      11-19-2020, 05:33 AM   #8
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Quote:
Originally Posted by richard in NC View Post
It's stock pads and sufficient depth per the track inspections.
There is your problem. The OEM pads are known to leave deposits on the discs when used on track which cause brake judder.

Its happened to two of my friends with F80 and F82s. Search the forums and u will find tons of posts on it.

Solution: Buy trackpads, bed them in, scrub the deposits, get vibration free brakes
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      11-22-2020, 06:57 PM   #9
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Quote:
Originally Posted by Megator View Post
Quote:
Originally Posted by richard in NC View Post
It's stock pads and sufficient depth per the track inspections.
There is your problem. The OEM pads are known to leave deposits on the discs when used on track which cause brake judder.

Its happened to two of my friends with F80 and F82s. Search the forums and u will find tons of posts on it.

Solution: Buy trackpads, bed them in, scrub the deposits, get vibration free brakes
What he said ^

Street pads especially OEM aren't ideal for the track even at novice level. The brake shudder is real and super frustrating...
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      11-23-2020, 03:19 AM   #10
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Quote:
Originally Posted by DRLane View Post
What he said ^

Street pads especially OEM aren't ideal for the track even at novice level. The brake shudder is real and super frustrating...
I had track pads for the M2C months before I even got it lol.
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      11-23-2020, 08:51 AM   #11
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Quote:
Originally Posted by Megator View Post
Quote:
Originally Posted by DRLane View Post
What he said ^

Street pads especially OEM aren't ideal for the track even at novice level. The brake shudder is real and super frustrating...
I had track pads for the M2C months before I even got it lol.
Well that sucks... 🙃

Ever tried a flex hone brush? Might be worth running over your rotors.
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      11-23-2020, 02:11 PM   #12
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I do need to get the car out and do a bedding in procedure. I've had good success cleaning rotors in the past.

However I don't think that is the problem. With pad deposits before, I've had low speed pulsing in the brake pedal with light pressure and a more chatter/out of balance feel at interstate speeds and moderate pressure. And can feel it in the brake pedal.

What I'm experiencing is only from high speeds and threshold braking effort that feels more like wheel hop, or possibly rapid uneven braking side to side in the back. But I don't feel it in the pedal. It's not ABS as that is a different feel and sound all together.
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