Shimano disc brake piston exposure tool

thingiverse

Shimano technical training offers a method for cleaning the pistons on disc brake calipers that relies on cutting down a bleed block, such as this design, to create a piston exposure tool. However, hacking apart a bleed block with a hacksaw seems like a workaround, so I came up with this alternative design that achieves the same effect without needing to break out a hacksaw. This design works similarly to a bleed block but specifically allows the piston to extend beyond the caliper enough for cleaning the side of the piston before pushing it back in and repeating the process with the other piston. Although this process is not documented anywhere outside of Shimano's technical education, you can understand the basic idea from the photos. Cleaning procedure: 1. Push both pads into the caliper. 2. Insert this tool. 3. Pump the brake and observe that the piston on the side of the tool with the cutout extends. 4. Stop once the piston hits the tool. 5. Remove the tool. 6. Clean the sides of the piston using rubbing alcohol and cotton swabs (Q-tips). 7. Lubricate the sides of the piston with Shimano mineral oil, the same stuff used in brakes. 8. Push the piston back into the caliper. 9. Repeat with the other piston. Park tool offers a video explaining this process without requiring a "special tool". Note: If you have Saint brakes or another Shimano 4-piston design, Mngnt has an alternative version that works for four-piston Shimano brakes.