Birzman Disc Brake Piston Pusher

The Birzman Disc Brake Piston Pusher is designed to make the maintenance chore of replacing disc brake pads easier by pushing the pistons back into the calliper. Unfortunately, it fails to achieve those aims in a meaningful and replicable manner.

When replacing disc brake pads, it is essential to first clean inside the calliper to remove any mud or road contamination from around the piston edge, and then push the pads fully back into the calliper ready to accept the new pads. As you use your disc brake and the pads wear, over time the pistons don't retract back as fully as they had. This is an automatic adjustment feature, which means that you can use your pads from new all the way down to replacement, without ever needing to make any adjustments yourself.

The tried and trusted way to get your pistons pushed back into the calliper is to use a 10mm (or so) ring spanner or plastic tyre lever, carefully centring the closed end of the spanner or lever on the centre of the piston and leveraging against the side of the calliper to slowly push the piston back. Another option is a large flat-bladed screwdriver inserted between the worn pads, allowing the screwdriver to push back against a large surface area that you don't care about damaging.

You can buy specific flat tools from the likes of Park Tool and others that will push back pistons in a similar, more-couth fashion. But with care, the ring spanner or tyre lever method is perfectly acceptable and will cause no harm to your calliper.

Regardless of your chosen method, it's critical to thoroughly clean around the piston, so you aren't pushing muck back inside past the seal and into the chamber with the hydraulic fluid. Best suggestions for removing baked-on build-up include using a very fine bottle brush, or a section of cotton string soaked in alcohol and sawed back and forth around the piston while clamping two £1 coins.

The Birzman Disc Brake Piston Pusher seeks to do this job in an even more couth fashion than any sort of other hand tool. By applying force evenly to both pistons at the same time, it slowly pushes them back into the calliper using a handscrew mechanism that applies pressure to both pistons evenly. This means that if one piston is slightly stuck, both will be pushed back without having to chase back and forth between the free and recalcitrant pistons.

In theory this is an excellent idea, but in practice it doesn't work in a consistent manner.

Firstly, there's the issue of clearance. On a number of bikes I found it quite challenging to get the tool inserted cleanly between the pistons in a way that allowed the tool to push back squarely against them. This could be down to either calliper design, where there is a small key to guide new pads in place, or where there is a disc brake mount in the way, particularly in the case of rear callipers bolted closely into the frame. To be fair, in the instructions Birzman notes that for bottom-loading callipers the calliper will almost certainly need to be removed in order to gain clearance. For top-loading callipers it's generally easier to find a way to get the tool in between the pistons.

Secondly, Birzman states that this tool is suitable for four-pot callipers. Again, nice idea, but there is no way that this 23mm-wide tool can push back squarely against all four pistons at once.

Recently I tested the piston release tool from R3Pro, which I have had success in using not only to release stuck pistons, but also to push back a stuck or final piston in a four-pot calliper with care, using a thin, flat-bladed screwdriver.

Finally, even if you can get the tool cleanly inserted between two pistons, the force against the pistons does not end up being applied squarely, resulting in at least one if not both pistons going in slightly askew and almost certainly binding.

I thought this might be down to user error and tried many different combinations of calliper, angle and amount of pressure. I only managed to get one calliper with known-working-well pistons to retract back cleanly.

> Everything you need to know about disc brakes

A scour of internet forums threw up a few similar comments, where purchasers found the tool didn't manage to work as promised. To be fair to Birzman, there were a number of glowing recommendations where it did work.

Conclusion

Owning a bike servicing business, piston pushing is one of the most common tasks I have to perform in the workshop when replacing customers' brake pads. So when I saw the Birzman Disc Brake Piston Pusher, I was keen to get my hands on it and see if it could make what can become a time-consuming and frustrating job much easier and quicker. Unfortunately, the reality did not deliver on the promise, and therefore I cannot recommend this tool.

• As a matter of course when a product scores below average, we put our findings to the manufacturer to give them the right to reply.

Birzman says: "All of our products have of course been carefully tested on as wide a range of bikes/frames/parts as we could get our hands on during research and development stage, and we would only state the compatibility of a product if it has proven to work over various trials. It is our responsibility as the manufacturer to ensure the effectiveness of the product after all.

"At the same time, we are aware that due to the diverse specifications of bikes available on the market, there are inevitably limitations, mentioned by the reviewer, to the product when it comes to certain frame/brake designs where the product may not perform as well."

Birzman also says it will be releasing a new Double Ended Piston Pusher, due around September: 

35 mm end for 4-piston callipers e.g. models from Shimano®/SRAM®/TRP®/Hope®

15 mm end for 2-piston callipers and callipers with unique structures e.g. Magura® MT5/7s

Verdict

Great idea that unfortunately is not delivered on by this tool in a reliable manner