Brake caliper rebuild

For more information and pictures, see How do I replace the brake pads?.

Supplies

For a deep cleaning

• DOT3 or DOT4 brake fluid DOT4 preferred
• Permatex ultra disc brake caliper lube or similar brake lubricant - Comes in brush-top cans, tubes, or small packets
• Disposable nitrile gloves (don't skimp on this one)
• Brake cleaner
• Plenty of paper towels
• Dentist's-type pick or tiny flat head screwdriver
• Heavy duty large zip ties
• Copper banjo bolt washers (optional) part #43067-001 WASHER, 10.5X15X1.5 - If you decide to go the recommended route below and take the caliper off the bike, you'll need two of these for each banjo bolt you remove.

Additional parts for a rebuild

If you're going to go to the trouble of taking your caliper all apart, you might as well replace the rubber seals. They're wear parts and are designed to be replaced every 20,000 miles or so, depending. It's $20-30 per caliper for the seals, but that's a worthwhile expense vs. having the brake fail at some inopportune point in the future.

Keep in mind that there are four seals per caliper and each has a different part number. Also note that the front and rear calipers are not the same and use different seals as well.

Notes

Throughout this process, use copious amounts of brake cleaner on every dirty part, then wipe and dry thoroughly. Not on the pads, though. The best practice is to keep every fluid possible off the pads. Air and water are okay, but anything else can lead to pads that get slick, get hard (providing less friction) or even get crumbly and wear away in just a couple of uses. It all depends on how the glue that's binding the particles (metal or organic) together reacts to whatever chemical hits it.

Procedure

Remove the two 12mm bolts attaching the caliper to the fork.

Gently remove the little brake pad and set it aside.

Pull back (compress) the caliper bracket, thus pushing the caliper guide pins in as far as possible.

Shift and tilt the big brake pad so it looks like this.

Push one edge of the brake pad over the caliper pin, allowing you to easily remove the other side shortly thereafter.

Your caliper should now look like this.

Remove the anti-vibration bracket (take note of its orientation).

Remove the ceramic (plastic) inserts inside the caliper pistons.

Pump the brake lever carefully and gently and work both pistons with your thumbs so that both pistons slowly pop out together. About 150ml of brake fluid will spill out, so be prepared with a catch container below your working area.

At this point you should consider unhooking the brake line so you can relocate the caliper to a convenient flat surface, such as a workbench. This will necessitate replacing the copper banjo bolt washers, but it makes the cleaning and rebuilding process much easier.

Remove all four (4) seals inside the caliper. Inspect them carefully; if they don't look perfect, replace them. Remember that all 4 are different and the front and rear calipers are also different from each other.

If you are reusing the old seals, clean them carefully and very thoroughly. There was a lot of dirt and unknown yucky stuff inside and behind these seals. This is why you should rebuild your caliper from time to time.

Reassemble all seals. Put one side of the seal in first, then work both ways around the rubber rings until they seat completely.

Pull out the caliper bracket assembly (the rubber boots should be worked off the bracket gently). One side of the caliper has a rubber boot which cannot be removed. Do not even try or you will destroy it. Clean it in place.

Clean and then lubricate the pins generously.

Spray tons of brake cleaner into the two caliper pin guide holes and make sure you get all of the old crud out. Then, insert a bunch of grease with your finger. The aftermath should look like so.

Lubricate and insert the clean pistons. Some people say to use brake fluid as lube; others use brake lube, as shown.

Push the pistons in with your thumbs until they are flush with the adjacent metal surface.

Insert the plastic (ceramic) inserts.

Install the anti-vibration pad.

Install the big brake pad.

Install the small brake pad. You must push down slightly against the anti-vibration spring to slide the pad into position. The corners of the pad fit into cut-outs in the caliper which are the same shape (rear caliper shown).

Reinstall the caliper, then bleed the brakes. Torque for the mounting bolts is 24 ft-lbs front and 18 ft-lbs rear.

Test the brakes while walking before going for a ride. It's more pleasant to realize something's not working when you're walking next to it than when you're approaching a stop at a busy intersection.