Having issues with some of your brake pistons not moving properly? If so, you could be leaving significant brake performance on the table. Luckily, it’s a fairly simple thing to fix if you’ve got the right tool.

Here's a tool that can be used on a variety of 2 and 4 piston brakes. The tool constrains all but 1 of the pistons so you can get the stuck piston moving with ease. Just drop the tool into your brake, pull the brake lever and hey presto, the stuck piston will move. Clean the piston with a cotton bud and gently press the piston back into the brake caliper with your tyre lever. If you want to clean them all, push them all back with your tyre lever and do them one at a time.

Put simply, this tool makes it easy to advance a brake piston as far as possible without popping it completely out of the caliper. This allows for as much of the piston to be cleaned as possible, which helps you maximise your braking performance.

The tool looks a bit odd, but between rotating and flipping the tool you can extend any brake piston. It also has a chamfer on the leading edges which makes it easier to insert in your brake caliper.

We promise that the tool doesn't look nearly as bad as the product image, we just have been without photography resources recently and wanted to list it anyway.

Cleaning procedure:

1. Carefully push all pistons back into the caliper using a tyre lever
2. Insert this tool. Put the retaining pin through the tool and caliper to keep it in place
3. Pump the brake and watch that the piston on the side of the tool with the cutout extends
4. Stop once the piston hits the tool - feel free to grab the brake lever a few times
5. Remove the tool
6. Clean the sides of the piston - we use isopropyl alcohol and cotton swabs
7. Push the piston back into the caliper with your tyre lever
8. Repeat with other pistons
9. Optional - apply a droplet of brake oil to the piston surface before pushing it back in. Only do this if you are going to douse the caliper with alcohol to clean it after the procedure, you don't want any rogue fluid hanging around!

While it is possible to perform this job on 2 piston brakes by carefully constraining 1 piston with a plastic tyre lever and pulling the brake lever, this tool makes it a whole lot easier and ensures you don’t pop the piston right out of the caliper.

Compatibility:

• Shimano 4 Piston - This tool works on all Shimano 4 piston calipers and will probably work on any other brake that can accept this brake pad type
• Sram Guide - Works for all Sram Guide brakes except for Guide RE - they use the Sram Code tool. The brake pad type looks like this.
• Sram Code - Works on Sram code and Sram Guide RE brake calipers. The brake pad type looks like this.
• Shimano 2 Piston (not road) - Works on all non-road/gravel shimano 2 piston mountain bike brake calipers as well as other brakes using either this pad type or this pad type
• Shimano Road - works on Shimano road and gravel brake calipers - or any brake using this pad type
• Sram Level and Elixer - Works on any brake using this style of pad, as long as the brake pads can be inserted from the top.

Here's roughly what the tool will look like when being used

Park tool has this video available which explains the process without using this tool on 2 piston brakes. It's the same procedure for 4 piston brakes, just use this tool.