While most know the importance of changing brake pads, few perhaps understand the necessity of maintaining both your pads and the brake pistons. Keeping them clean and in good order contributes to optimal braking and in the case of seized pistons is an essential skill to get them working again.
Tools you’ll need to clean, repair and rebuilt your calipers are:
- Both 1500 and 800 wet and dry sand paper
- Wrenches and sockets
- Brake Piston removal tool
- Brake fluid
- Brake cleaner
- Specially formulated grease for brakes
Let’s begin by removing the pads from the caliper. You’ll first need to remove the pad pin or pins (1) which holds the pads (2) in place. Once you unscrew that you can remove the brake pads. There’s usually an anti-rattle shim (3) beneath the pads too – it’s probably a good idea to take a photo of the shims location as it’s not always obvious when you return everything back together.
To properly clean your calipers, you’ll need to disconnect them from the brake line. That means you’ll need to bleed your system when you reinstall the caliper. If you don’t want to do that, you won’t be able to remove the piston(s) and it will be a little more difficult to give the caliper a thorough clean.
On the basis that you are going to clean everything, loosen the banjo bolt that connects the brake line to the caliper and for the meantime, tighten it up by hand. This allows us to release pressure in the system so that we can remove the piston.
We’d recommend using a proper piston removal tool like the one we have from Bikeservice. It works by being placed inside the piston and gripping it internally and saves a lot of time and headaches for a job like this. Whatever you do, don’t grip the outside of the piston when trying to remove it – you’ll potentially score or damage the piston that way and that will lead to a leaking and ultimately useless brake piston.
An alternative is to completely disconnect the banjo bolt and spray compressed air into the hole, pushing the piston out.
Now onto cleaning. Make sure that you only use proper brake cleaner as certain cleaning fluids don’t play nicely with the seals inside the piston. We’re using a brake cleaner from Motul. You can use a metal brush on bracket and other hard parts of the caliper, but keep it well away from the piston, cylinder and the pads. To be safe, just use an old toothbrush in conjunction with the brake cleaner.
For the piston itself you can clean it and remove any dirt, rust or grit with 1500 grade wet and dry paper in conjunction with brake cleaner. For the pads, clean them with 800 grade wet and dry. Don’t forget to clean the backs but just as importantly, the sides and the whole where the pad pin goes.
Once everything is cleaned up but before we reassemble, we need to apply some grease to the backs of the pads and the pad pin. Some people decide to forgo using grease on the backs of the pads which essentially just reduces noise, but seeing as you have to use it on the pad pin(s), we don’t see any harm in it. Just make sure you use properly formulated brake grease – it needs to be able to withstand extremely high temperatures and be water proof.
Now, time to reassemble. Put some brake fluid on both the outside of the piston and in the cylinder, then push the piston in by hand. It should slip in nicely. Next, place the anti-rattle shim back to its original location and then the first pad – place the one that sits up against the piston first and/or is on the side that the pad pin first enters. Place the opposing pad and then thread through the pad pin(s). Check to make sure that the anti-rattle shim hasn’t moved while doing this. Re tighten the pins to the manufacturer’s recommended torque levels.
Now return your caliper to the bike and re-bleed your brakes. We’d recommend that for the first few kilometres, treat your brakes as if they were brand new and go easy on them. Do a few low speed emergency stops too.