courtesy of Jens Lyck


Brake caliper overhaul - how-to guide.

When your bike is 10+ years old, chances are that your brake calipers need a service check. You may have noticed that the bike doesn't brake as good as it used to.

Before you spend a lot of money on fine exotic brake parts, you may want to consider to do an overhaul on the existing parts. You'll probably find one or more pistons stuck due to dirt or rust. The chrome plated iron pistons, used in some models, have a nasty habit of parting the chrome from the pistons after some years of service. This makes the pistons rust and then they get stuck in the bore.

The guide found below, tells you how to do an overhaul on the common Brembo F08 calipers. You can easily use this guide for other calipers, the difference is mostly in the number of pistons, and how the brake pads are installed.

It's not that hard, but you have to be careful when you are cleaning the parts and when you reassemble the unit.

NOTE - you'll want the brakes to function properly when you are finished. What I'm saying is that you have to be certain that the hydraulics are not leaking and without air bubbles in it before you take the bike for a ride. Having no brakes is lethal !!!!!

NOTE - The rubber seals may be destroyed if cleaned in kerosene. So if you want to see if seals are reusable, remove them before cleaning the metal parts in kerosene.

Now, let's get to it:

Apart from ordinary hand tools you'll need the follow:

  • Clean rags
  • Cotton rolls and brushes
  • Kerosene for cleaning
  • Gasket set
  • New pistons (if needed)

Start by removing the calipers from the bike and take the brake pads out. On the F08's you remove the plastic cover, activate the spring in the middle, and push out the two long pins (They may need pushing with a small hammer).

Picture below shows Caliper with plastic cover removed.

This is how pins, spring, and pads are assembled.

When the brake pads are removed, you should be able to see something like this.

The caliper housing is in two halves, held together by two large bolts, but try to make the pistons move before you take the two halves apart.

Put a spacer (two brake pads are fine) between the two pistons, and apply pressurized air to the caliper inlet. Don't put your fingers between the pistons, because they will slam together with great speed. without the spacer, one of the pistons will leave the bore, making it difficult to loosen the other.

If only one of the pistons are moving, you'll have to invent something to hold it firm in its bore. Then you can make the other piston to move the next time you put pressurized air to the caliper.

Once the pistons are freed, you can take apart the caliper housing, and remove pistons and seals.

Be careful when you are removing the seal half way down the bore. You need a small screwdriver to get is out, but take care not to scratch the bore.

Picture below shows two chromed iron pistons - ready for the dirt bin.

Cleaning time. All parts are cleaned in kerosene with the brush, to remove the dirt.

The rubber parts do not like kerosene, as mentioned above, so if you want to reuse them, they must be cleaned in water or brake fluid.

You must be very careful at this point. Use clean rags and cotton rolls. All dirt must be removed from the bore in the housing, also in the grooves for the seals. Cotton rolls are handy here.

Remember to remove all traces of kerosene. If you are not sure that the kerosene is all gone, flush the parts with tap water and dry again.

Next picture shows the cleaned and dried parts.

Left is the gasket set, right is the new aluminum pistons

..... close up on the new pistons.

At last! Now you can put everything together again.

The gasket set contains a small amount of high temperature grease. Apply a thin layer on all seals and to the piston where it meets the bore.

Note how easy the pistons move - its a whole new world.

Reinstall calipers on bike, apply brake fluid, remove air, drive. That's it!

Do remember to double check all fasteners - oh, am I repeating myself here.......

Good luck!