Reviving an older thread, I change the fluid often, but i did not remove the rear caliper this year for cleaning and lube and it almost bit me this past weekend, just touch rear aggressively at speed and lock up, locked up probably 5 times running the Devil’s Triangle, not cool, very dirty, sliders working halfarse, and unsafe, scraper pin had come loose also because of road grime pushed it loose on one end and was scraping brake pads, I corrected it today and hope it never gets me again. Service the calipers guys mine hasnt been long since i did it last and it almost got me running a dangerous mountain.