Brake Caliper Rebuild

If you're short on cash, here's what I've done many times with great success if your hydraulic brakes are hanging up.

Be sure to read all of this write up before starting!

As with all information found on the net, USE AT YOUR OWN RISK!'

First, find out what is causing the caliper to keep pressure on the pads when there is no pressure put on the master cylinder lever. Do this by:

1. Put bike on center stand and lift front wheel off of the ground. 2. Squeeze the brake lever and release it. 3. Rotate front wheel and confirm the caliper is putting pressure on the pads. 4. Without touching the brake lever, open the bleeder on the caliper. If fluid comes out under pressure, either your master cylinder or brake hose iscontributing to the caliper hanging up. If just a little brake fluid comes out, proceed with the following. 5. If you are lost at this point, I would suggest not working on your own brakes. Not trying to be a jerk or putting you down! Hope you understand.

If the rubber parts aren't damaged with cuts or tares or swollen, I've been able to reuse them many times. The brakes work fine with no leaks. The piston slides in with just thumb pressure. (No leaks and ease of movement are the goals here.)

This can be a guide for installing new rubber parts (kit) in a caliper too.

The stuck piston(s) were forced out of the caliper with the pressure of the master cylinder. The caliper was hanging up so bad the bike was hard to push and I could feel it while riding. The caliper tightens up because crud forms in the groove of the piston seal making the groove smaller and the rubber seal pushes harder against (squeezing) the piston. Also, the external slider pins can be frozen/corroded causing brakes to hang up.

Don't use anything but brake fluid and a CLEAN rag to clean the rubber parts. Brake cleaner will swell and deform them in short order. Don't believe me? Try it.

Be sure the piston rubber sealing ring is clean (clean with brake fluid and a clean rag) as well as the groove it sits in.

If it's not rubber, brake cleaner can be used.

After all of the rubber parts have been removed, use brake cleaner to clean the caliper body. Be sure to clean ALL of the crud out of the piston seal. I've scraped this groove clean with a small screwdriver, dental tool or what ever will fit in there. The piston only touches the rubber seal. It does not seal against the caliper cylinder wall. However, be sure the caliper cylinder and ports are free from crud.

Be sure the brake bleeder screw is not stuck and it's hole is open. I use a small dab of anti-seize on the threads. Put the anti-seize just on the threads and be careful not to get it inside the bleeder hole. I don't know what anti-seize will do mixed with brake fluid and do not want to find out.

Be sure the external slides (not the caliper piston) are clean and lubed with a high temp synthetic brake grease.

Lube the internal parts (piston seal and piston) with brake fluid during assembly.

After the piston is started into the caliper cylinder, (this can take a little wiggling) it should only require the force of a thumb or two, once it's square in the caliper cylinder, to slide all of the way in. Be sure to get your road/dust seal positioned on the grooves of the piston and caliper before you get the piston pushed all of the way in.

If you haven't tried the above, please try it before flaming me. Since I was a kid, I've played/worked with brakes and other mechanical things. You are responsible to assess your own skills.

Keep in mind that the goal, that also was mentioned above, is to have a caliper that slides easily, and is leak free.

As with all information found on the net, USE AT YOUR OWN RISK!

Credit

DanCX500