Stick with your HCR..............those Rev Summits were lumber wagons....pretty much hadn't figured out how to work off trail and sturned like locomotives.
HCR is a great machine, pop on the mountain seat and rip it. My Oh 9 Crossfire was still one of my favorite sleds ever.
How many miles on the HCR? Coud be a bad bearing behind the disc. Really only thing that failed on my Cat at 5000 miles, with Webba, about 4 hours from the truck.