How do you get the rear brake caliper piston to go in?

To retract the rear brake caliper piston, you typically need to use a brake caliper tool or a C-clamp. First, remove the caliper from the bracket and ensure the brake fluid reservoir cap is loosened to prevent pressure buildup. Then, either compress the piston gently with the tool or use the C-clamp to push it back in, ensuring you do so evenly to avoid damaging the piston. Always check for any rust or debris in the caliper before reassembling.