Brake Caliper Rebuild
Continuous brake issues could mean internal issues.
What's Needed:
This is largely dependent on the type of brake system you have, but this should cover most modern systems.
- Wrench to disconnect brake line from caliper (13mm in our instance)
- Small plastic bag to catch brake fluid
- Allen to loosen and remove the caliper from the chassis. (6mm t-handle allen in our instance)
- Pliers to remove clips from our brake pad pins in the caliper OR screw driver to remove screws that hold the brake pads
- Compressed air to help break loose brake pistons
- Piece of cardboard or similar to deaden the blow from the pistons breaking loose
- O-ring pick tool
- Grease
If you're facing continuous brake issues and you've changed your brake pads, you've tried scuffing up your rotor to get friction, or you've bled your brakes by following our brake bleed video, then it may be time for a brake caliper rebuild. This is not something you do when you're pinched for time as we'll be removing the caliper from the chassis and cleaning it out.
Rebuilding your brake caliper
To begin, start to disconnect the brake line(s) from the caliper. For us, this is a banjo fitting that we can disconnect using a 13mm wrench. Before completely removing the line, get a small plastic bag ready. Now completely remove the line from the caliper, putting the bag around the line and sealing it up as much as you can to catch the brake fluid, washers, and banjo fitting.
The next step is to remove the caliper from the chassis so we can work on it in a clean, open space. Our setup needs a 6mm t-handle allen wrench to disconnect it from the chassis. Please note, in our video we have the axle removed, but you can disconnect the caliper with the axle in.
With the caliper in hand and you've moved to a clean, open space to rebuild the caliper, we need to get the brake pads out. Our setup has the pads held in with pins so we remove the clips that hold the pins; then the pins slide right out. Some brake caliper systems use screws and tension springs to hold in the brake pads. Remove those screws and the pads will fall right out.
The brake pads are now removed and we now need to break loose the brake pistons. To do this, you need to shoot some compressed air into the inlet where the brake line was connected. This compressed air will force the pistons loose and out of their pockets. Before you start on this, however, get a piece of cardboard or similar so that when the pistons do break loose, you have something to deaden the blow that's not your hand. Keep your fingers clear of the pistons so they do not get smashed! Inspect your pistons for any dents, cuts, or burrs.
The only items left are the o-ring seals that were behind the pistons. Some may have come out with the compressed air, but most likely some are still in the caliper. Fish those out with an o-ring pick tool and line them up on your table. Inspect them as well for any tearing to insure they're still able to seal properly. You should also check the pockets where the pistons were sitting to insure there are no rub marks. This could be a sign of the piston coming in direct contact with the caliper body which it should not be.
After everything checks out, it's time to put it back together. You may need some light lithium grease to lightly grease the o-rings and pistons so that nothing binds up when you're putting everything back in. Because you were organized, your o-rings and pistons are in order on your table and you can begin putting those back in in the reverse order you took them out. O-rings first followed by the pistons. Some o-rings only fit a certain position, so make sure you have yours in the proper position of the caliper. Reconnect the brake pads, pins, and clips as well.
To finish it all up, reconnect the caliper to the chassis, the brake line to the caliper, and bleed your brakes. Hand tighten the brake line fitting initially before putting a wrench to it. This will insure nothing gets stripped as these can be a sensitive area. Do not over tighten the brake line fitting. This could over crimp your washer or cause small fractures in your fitting. Only tighten until you feel good resistance. Finally, do not forget to bleed your brakes! We have a video on that as well if you are unfamiliar with the process.
TL;DR
- Disconnect brake line from the caliper and remove the caliper from the chassis.
- Remove the brake pads from the caliper.
- Brake loose the brake pistons by using compressed air into the brake line inlet.
- Remove the o-ring seals from behind the pistons and check for any tearing.
- If everything checks out, put the seals and pistons back in. Use some light lithium grease if needed.
- Reattach your brake pads to the caliper.
- Reattach your caliper to the chassis and brake line to the caliper
- Bleed your brakes
