Rear 10.75 Goodwin v4 disc failure (now with PIC)
 

So what happened here?
Too much heat in rear?

https://www.miataturbo.net/attachmen...ine=1369589268

I want pictures of failure!

hmm... thats odd.... i cant imagine THAT much heat building up in the rear, especially being big and slotted, and... in the REAR... maybe a manufacturers defect????
how old are they?

Dunno what happened. Rotor fairly new (2 days) and torqued to spec.
Or I missed a minor crack and this developped?!

:eek:Should dissipate heat better-LOL

2 days, or 2 track days?

The only time I've cracked a rotor (a front) was after a tranny failure at Laguna where I pulled off track and wound up sitting there with my foot on the brake for 5 minutes (so it didn't roll downhill back onto the track) waiting for the tow truck. The lack of a cooldown lap really does make a big difference.

--Ian

I had an identical crack (2-3mm gap at the rim) in a OEM rear rotor (251mm) that I noticed first when I was preparing for the next race. I have no idea if it developed during the race or sometime afterward (small elves killing rotors). That crack was clearly noticeable so I don't think I could have missed it at the track.

Wet race meaning sudden cool down?

I've done no wet on this rotor. The only thing I can think of would be no-cool-down-lap-pit-in-handbrake-on-crack.

My vote is on a sticking caliper/caliper sliders. I see other thermal cracks as well. Rears should last 20 days, not 2.

If that includes overtightened parking brake adjust, you could have a point... switching to M-tuned kit with sport rotors soon so I can at least source replacement parts locally.

Sometimes you just get a bad rotor.

Switching to M-Tuned and sport rotors in rear: cheaper and easier replacement.