For a update I took the rear wheels off, brake pads are good.
It looks like the caliper is rattling on the slide pins.
When you apply the brakes the noise is gone.
OK just cuz i do all the work on my buds rzr i saw this , we put a lift and 27s on it went to the big horn for a weekend and he had brake fade bad the 1st day out and blew all the fluid out on the trial , so he had a white knuckle ride back . Filled the fluid up , all good , so far . Other than that , ???? good luck .