Clunk under hard braking

[SSJTrunks523]

So after melting my stock pads on my 2nd session of my first track day at LRP, I just had a ST60/40 F/R kit installed. During the bedding process, I have noticed that I get a substantial clunk from the rear. Unfortunately these cars make a lot of noise and searching "E9x rear clunk" isn't really helping. Any thoughts on what it might be? Coming from the rear, sounds like diff area. Hard braking (bit of lock), 60-80 down to 10, probably around 30-10mph in the decel generally.

I'm also finding that not a lot of people seem to do Front and Rears, so that's not really helping me find info.

I am going to play with settings and try to turn off DSC completely. Trunk is empty, incl all factory included items.

E92 ZCP DCT

PFA - Don't mind the dirt haha

[R3dliner]

How was the track session? I missed out. Was suppose to go that day.

Do you hear a clunk when you ease off the throttle or just when you brake?
I would inspect your driveshaft where the U-joints are and the guibo disc.
Most clunks seems to driveshaft related. Look to see if your diff bolts are well intact. I've heard people snapping bolts.

[SSJTrunks523]

It was great! I was there June 9th-10th for HOD. My brake pads melted and my RE71Rs were greased garbage after a couple laps, but I really got a much better feeling on the car. Purchasing dedicated track wheels and tires right now. I learned a lot about conservation haha. Once I got better at limiting brake use (since I was wobbling hard under braking from rotor deposits) and tire management (since they greased so bad), I ended up needing to keep engine temps down (have do88 water rad only).

The noise is only under hard braking. Not at time of release. I'll have my local put it in the air and take a look. I only have about 100mi on the new brakes. It's a sunny sunday, Autox and Track only car.

[R3dliner]

Last time I was there I always would mess up on the dip in the last apex. Never been there with the M yet and I wonder how it will play out.

Good to know your heating issues.
hmmm if that's the case it doesn't seem driveshaft related. Have you retorqued the caliper brackets? I'm not too keen on the ST60 kit.

[SSJTrunks523]

I didn't install. I'll take a look and ask them to re-check. I got the kit VERY cheap. The ST40 would be the part making the clunk as it is in the rear.

I hit ~150mph on the main straight (saw 147/148 a couple times), ~120mph on No Name even with that damn lip lol Didn't time a lap, but I got asked by a few people what I had done to the car. That last apex before the big straight is monumental to your speed. Had a guy in a C5 Z06 with a C6 BBK ask me how I was faster. His line was horrible on the last apex and he entered 15-25mph slower than I did.

It was mid-80s and the track was hot to give you an idea. Lots of people complaining on the second day that tires were grease, esp in the afternoon.

[SSJTrunks523]

So.....i believe this is just hard/bad wheel hop and lock. Warmed after multiple hard stops and with edc set to the hardest setting, it did not replicate (though I was only coming down from ~40ish). When one tire locks, I can hear it squeal a bit and it's really rough, but this must be what it sounds like when both rears at the same in a hop situation. I've only ever experience rear lock on my R6 (no abs) and my Camaro (without abs and shit tires). Neither hop, just a nice controlled rear slide. I'm slightly concerned as to how this will feel on track. Doesn't give me confidence.

[R3dliner]

Maybe it's time to upgrade to coilovers?