Intense Brake Judder…that Disappears Under Threshold Braking
 

I just wanted to post this thread to help anyone else trying to diagnose the particular brake judder issue I was having. Here were my symptoms:

1) No braking issue (judder) at the track with track pads at about 75% pad remaining.
2) As the weekend progressed I started to notice a slight judder under braking.
3) The judder got progressively worse after each subsequent track session. The judder was more pronounced under trail braking.
4) By the end of the weekend, when my pads were <25% remaining the judder got so bad the car felt dangerous and trail braking was all but impossible.

Now the key symptom.

5) If I just kept the car in a straight line and applied 100% braking force (aka threshold braking) the judder would disappear and my braking would be smooth. However, when I backed off to anything less than threshold braking the intense judder would reappear.

Rather than go into the multitude of possible fixes I will let you know what worked for me. I suspected that the issue had something to do with the pistons when they were overly extended. Maybe sticking, maybe the years of track use has slightly rounded out the caliper seats, who knows.

My fix was to take an old set of street pads and use a hammer and chisel to remove all the remaining pad material creating a backing plate. I then cleaned the caliper and pistons best I could and lubricated the pistons with plenty of brake fluid. After compressing the pistons I inserted the backing plates behind my badly worn pads and voila! The judder is completely gone!

So the problem did have something to do with the over extension of my caliper pistons. If you ever run into this problem I hope this helps.

interesting! probably not pad deposits afterall as we all thought. Makes total sense.

Wish you figured this out 4 years ago, would have saved me the $7000 I spent on the stoptechs because I didn't want to deal with it! ;)

I am glad at least someone found this helpful. Who knows, maybe this is a problem with our sport brakes.

All I know is that there is nothing worse than trying to track down a mysterious source of brake judder.

Interesting is right. From reading the above. It seems when the pads are worn down to <25%. There is not enough brake piston in the bore. Allowing the pistons to cockk in the bore? So, solution is to get longer caliper brake pistons. Next question. Who makes them?

I work on minimum pad thickness including backing plate of 12mm and with 5mm backing plates this is 7mm of pad material left which is a key heat insulation contributor

I work on around 13mm of effective pad material to use before replacing pads.