BRAKE CALIPER MAINTENANCE
The recent Covid 19 virus had certainly taken a toll that saw many of us being locked down. So with the extra time available, I was glad to receive this opportunity to share an idea on what I believe to be the best way of preventive maintenance for your disc brake calipers.
Typically, a brake caliper system maintenance would only consist of 2 chores which are; To renew brake fluid by the conventional bleeding process or to disassemble the caliper and change the seals, and o rings if present.
However, there is another proven option in between which is to reverse bleed the system frequently ( i.e. 4 to 6 months ) so that the seals can be exercised thoroughly. By doing so and with the method as herein mentioned, the deep cleansing of the caliper pistons will also delay the wear on the seals. As such, any cost to disassemble the calipers and to change the seals can be delayed, tremendously.
HOW IS IT DONE?
1) Try to obtain a service manual specific to your brake caliper as this will offer the torque values when re-installing the pads that you will remove from the caliper for this exercise. Attached with a less complicated blown up image/parts diagram of the rear caliper for your viewing pleasure and understanding.
2) After removing the pads, remove the caliper away from the disc ( remove from the bracket attached to the fork if it’s a radial caliper ). You will basically be able to hold or almost hold the caliper in your hand with the fluid line attached..Here you are also exercising the hose tip from hardening and or cracking.
3) Pump the brakes till pistons come out to a fair amount with just about enough room for the piston wise grip tool to fit between.
4) Brush the pistons with neutral soap water using a toothbrush. Rinse with water.
5) Turn the piston using the piston tool. ( do not grip from outside- a scratch to a piston will cause a leak and most probably damage the seals.). Now you will be able to brush the part that could not be accessed earlier. Rinse with water again and give it a few minutes to dry up.
6) Open up the brake fluid reservoir. Syringe out 90% to 95% of whats in the reservoir and transfer that to a separate bottle for disposing of the fluid later. The syringe cost is only about RM1 in a pharmacy
NOTE: Brake fluid is hygroscopic so please dispose of appropriately and not into the drain. Normally I would collect all changed oils and pass it to any mechanic shop. They will sell it back to the recycling guys.
7) Use the piston separator tool to separate the pistons fully but slowly. This tool will help NOT to squash the seals at a particular area as the forces are equally distributed. If you are working on a 4 piston caliper, do 2 pistons first followed by the other 2. You SHOULD insert and leave the separator tool between the 2 pistons not being worked on so that it can be opened fully again before reinstallation of the pads.
Monitor the reservoir as you do this separation because the fluid that was in the line/hose will return to the reservoir. You want to avoid the fluid in the reservoir from getting onto the bike so syringe out again leaving only about 5% in the reservoir. This is so that you won’t get an airlock while if there is a bubble in your system line, it should come out when the fluid is pushed upwards.
NOTE: Refill the reservoir before doing the other 2 pistons/pumping again and the same if it is a 4 piston caliper if you are about to work on the next caliper. You do not want to introduce an air bubble between so NEVER have an empty reservoir at any given time.
8) add in new brake fluid of the same DOT specs. Mine uses Dot 4. A 1-liter bottle of Bosch DOT 4 which is approximately RM 20 will last you 8-10 times of this exercise easily.
9) Re-assemble the caliper and pads in reverse order, tighten the sliding pin according to torque specs. Do be sure to wipe the sliding pin and apply new grease on the sliding area of the pin.
10) Refill the reservoir accordingly and tighten back the cap. Give it a few pumps and voila, you’re good to go.
By the time you repeat this process for the other caliper or twice or 3 times on a single caliper such as my rear caliper in the photos, you have already achieved the equivalent of bleeding in new fluid, removing potential air bubbles that will cause sponginess and..
- a) Without touching the bleeder nipple where you might over-tight and have a headache thereafter.
- b) You have a clean piston that can slide in and out smoothly, offering effective braking and release.
- c) Your piston will not seize whereby the brake remains applied even after you release. This has in the past caused motorcycles to skid and crash which is what you want to avoid.
- d) Lastly and most importantly, your super clean pistons will not mar the seals and thereby prolong its life. This will delay the ill effects and cost of having to disassemble your calipers to replace the seals.
Wish you well & safe riding always,
by Shamalan Jeyasingam