16. REAR BRAKE/REAR FORK/REAR WHEEL/REAR SHOCK ABSORBER DOWNTOWN 125 i 15 Compressed Air Remove the piston from the brake caliper. If necessary, use compressed air to squeeze out the piston through the brake fluid inlet opening and place a towel under the caliper to avoid contamination caused by the removed piston. Check the piston cylinder for scratches or wear and replace if necessary. Check the caliper cylinder for scratches or wear and measure the cylinder bore. 16-4