Composite Rotor Meltdown
MMC is a material that melts on higher temperatures but that is not where the problem begins. There are different manufacturing processes to make MMC rotors. I am familiar with 2, squeeze cast and spin cast. Squeeze casting can cause air pockets and spin casting eliminates the air pockets by rototing the casting/ingot and the ceramic (silica sand) goes to the outside and makes the outside edges harder.
I doubt this is your case but I believe quarterbacking on Monday from the arm chair that your calipers were not centered on the rotors. I do an alignment process and make sure my wheel spins 1 1/2 rotations before stopping by the drag of the brake pads. When your calipers are out of alignment the brake pads drag, heat up the rotor, and cracking than explosion happens. There is no recourse for the vendor to protect themselves against operator error on installs. MMC works on race bikes but there are better materials that have a higher coefficient of friction.
Melted because you ran the bike too hard = extremely doubtful, exploded because of an alignment problem, the most likely explanation. I have no dog in this fight but I do have a lot of experience with MMC.
A different manufacturer's rotors with aligned calipers lasting well over 5 years with absolutely no wear and I guarantee I run this bike much harder than 99.99% of other HD riders into the corners. Your results may vary as this is not the same manufacturer or manufacturing process. Good luck.
Makes me wonder if it was a failed wheel bearing on the rotor side or something that caused a side load maybe? I dunno.
Crazy though...
lp
I live in Colorado, we have quite the elevation and passes here. I hardly ever use my brakes unless I am slowing down for stopping traffic. I took my wife for a ride up Boulder canyon and back down Coal Creek canyon and used the brakes maybe once or twice until I came to the stop light at the end of the canyon. Need to use the engine to keep the bike at lower speeds.
I took several test rides, as I had done other work (suspension) on the bike that I was checking and each time I returned I would check the temps on the rotors they were between 38 and 42c each time. Then I went on about 20 mile ride and touched the rotors they were warm to the touch. After that is when I went to the mountains.
Since I put my stock rotors and new HD pads back on the bike, I am not having any issues with nearly 300 miles logged since.
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