How to strip and rebuild motorbike brake callipers

Back to Basics Bike Maintenance with Bruce Dunn - Seized Brake Callipers

Binding brakes is usually a symptom of a build up of corrosion within the calliper, and often happens after you have left a bike for a week or two (or longer). When you eventually come to move the bike you'll find it difficult to push, and squeezing the brake lever can make it worse as the piston struggles to slide back into the calliper.

The combination of corrosion on the pistons, as well as the seals becoming distorted, conspire to prevent the pistons moving as they should. Coupled with this, corrosion can set in behind the seals where they locate into the calliper, and the oxidisation of the alloy destroys the working tolerances. In the case of all these scenarios, a calliper refurb is the only way to remedy things.

Step 1 - New Suzuki service parts pads and seals

A brake calliper contains moving parts and over time they need cleaning and servicing. This need is often accelerated when the bike is used in the winter and you discover that the brakes start to bind, and get worse. Typically the parts that need cleaning are the main body of the calliper, the pistons and the bore which they slide in. The serviceable parts are the dust and fluid seals, and the O-ring(s) that seal the two halves of the callipers.

When it comes to sourcing parts to refurb your brakes, for most common bikes you'll usually find the originals are readily available from your main dealer. Luckily for Project GSX-Reborn, Suzuki handily offer a complete brake rebuild kit for most of their models, old and new, including the GSX-R600 K3. Bingo!

Step 2 - Removing the brake pads and pins

Remove the calliper from the bike, undoing the hose and calliper mounting bolts. Working on one calliper at a time, loosen any brake pad retaining pins and remove the pads. If you are re-using the pads it is good practice to make a note of which side of the calliper they were fitted to. If there is an anti-rattle shim make sure you know how it fits for reassembly; taking a picture of it before you remove it can really help here.

Step 3 - Cleaning the exterior of the calliper

Prior to stripping the calliper in half, give it a clean with bike cleaner and a brush. Treat it like a pre-clean, the idea is to remove any heavy deposits of road dirt and dust. Soak it with cleaner then agitate the dirt until it yields, then rinse off with water. If you are re-using the pads don't use the cleaner on them, simply give them a light brushing over with a fine wire brush.

Step 4 - Splitting the calliper in a vice

Put the calliper in a vice and then undo the bolts that secure the two halves. Make a note of which bolts go where if they are different lengths. Just before you have the two halves split, keep an eye out for the O-ring(s) that are located in the centre of the bodies - these are going to be replaced anyway, but keep them to make sure that the new ones match.

Useful Tip: Use a heat gun to make the calliper hot, this will help loosen bolts and the pistons.

Step 5 - Using brake piston removing tool

The pistons in the callipers need to be removed for cleaning. The easy way to do this is to ease them out with the correct tool – a calliper piston tool. This tool grabs the callipers from the inside so will not damage the chrome outer at all. Don't use mole grips or pipe grips as they will almost certainly slip and damage the piston. When the pistons are out, undo the bleed nipple and give it a clean.

Useful Tip: A Calliper Piston Tool saves damaging the piston surface, £18 well spent!

Step 6 - Unpicking the seals

As the piston comes away, be prepared for residual brake fluid to spill out. Pour this fluid away and then, using a fine pick/hook or very small flat-bladed screwdriver, ease out all of the seals. The typical layout is the upper thin seal is for dust, and the second thicker seal retains the pressurised brake fluid.

Step 7 - Cleaning the stripped out calliper

You can now start to clean the inside of the calliper, look for any corrosion build up behind the seals - this can be a bit tricky to remove and the best way to tackle it is by using a fine wire brush, or a scotchbrite pad soaked in brake cleaner. Clean any area in the bore that looks like it has started to corrode in any way. Avoid cleaning the machined area where the two halves meet, this should be free of any contamination.

Step 8 - Cleaning the pistons

The brake pistons will mostly be in good condition, it's usual for the top part that is exposed in the air to get dirty and tarnish, but this can be cleaned up by using a metal cleaner like Autosol. You can also use a mop on a Dremel or drill at a low speed to help speed the process up a bit. Once the cleaner has been applied, switch to a buffing mop and finish off by polishing all over. An alternative would be to use a nylon brush attachment.

Step 9 - Fitting new rubber seals

Prior to fitting the new seals, give the calliper a thorough blast of brake cleaner and then blast with an airline. There are two seals per piston, the one at the top is the dust seal, this is usually thinner and has a double lip, and the other thicker seal is responsible for keeping the pressurised brake fluid contained in the calliper. Check the workshop manual, sometimes the brake fluid seal is subtly shaped and has an up side.

Step 10 - Replacing the Pistons and O ring

Push the cleaned pistons back into place, a very light smear of brake fluid on the lower seal is all that should be used to help them in. Push them in all the way until they have bottomed out. Then using the new O-ring(s), join the two halves together carefully and tighten up evenly. Use a torque wrench set to the spec listed in the owner's manual then tighten the bolts up. Replace the brake pads and retaining pins.

OEM rebuild kits vs. Pattern Parts

If you don't opt for the OEM parts (or can't find them), there is a ton of stuff available online, but the world of pattern parts is a bit of a lottery and you might be exposing yourself to some poor quality stuff – which you don't really want when it comes to critical braking components... Therefore, stick with a UK supplier; my go-to people for aftermarket brake bits is Powerhouse.uk brake calliper rebuild kits [this link takes you to a video of the rebuild process], including pistons, and will also rebuild your callipers for you, if you're lacking the confidence.