Putting new seals on the brake piston

What's the best way to get the outer seal onto the brake piston and caliper body? Should I put it in the body and slide the piston in around it or should I put the piston in and jam the seal in over it.

I think I'll be good for the inner seal

What's the best way to pull the piston out of the caliper?

I install the piston and then put the dust boot on.
The seal is inside and goes in while the piston is out.

-Duck

Ok. I have the inner seal done, and the piston back in but I can't seem to get the lower lip of the dustboot settled down into the caliper.

The seal is easy. The dust boot was not. I ended up putting the inner piston seal in the caliber, then putting the piston PARTway in to where it gets past that seal, then putting the boot rings in the caliber slot and piston slot, then sliding the piston in all the way. I figured this out after running into the same problem you're having. It helps to lube the piston just a bit with a film of brake fluid.

Post edited by: bluegill, at: 2006/02/01 22:01

Is there a good way to get the piston back out? It sort of slid out the first time for me, mainly I'm guessing because my inner seal was nonexistant

I still can't get the piston back out or the bottom lip of the dust boot in. Can I use WD-40 to pop it back in the groove? I know that lubricant near brakes is bad but I'll still be spraying down the disc and pads with brake cleaner when I get it all mounted back on.

I don't have long finger nails and I don't want to use a screw driver to push it down for fear of putting a hole in it. Any other ideas to push it into the groove?

push piston out with brake fluid and master cylinder

you can work boot in by rubbing/stretching it's not particularly delicate but don't nick it.

it's winter, this will be much easier by a warm stove in the kitchen with nice warm parts the boot will be easier to work

you can use some brake fluid for lube. anything else will end up behind the boot and work it's way out onto the pads when the brakes get hot. With spirited riding they will get very hot.

you might try getting the boot seated in the piston groove, rolling it over so the other lip is inside out and then rolling it over and into the groove on the caliper

again, it'sd not particularly delicate so long as you don't nick it.

-Duck

The best way to get the piston out is too use air pressure. Here's how I have done it:

1. Use an old brake line that you have first cut off the round head part of the banjo fitting at the far end. That will leave you with a metal tube that you can hook a clamp-on air pump nozzle onto, just like you do when inflating your tires.

2. Mount the uncut end of your modified brake line onto the caliper.

3. Place some folded over rags into the caliper where the piston end is located. (This will keep your piston from shooting across the room and wounding the cat, or your kids. It will also catch some of the brake fluid mess.)

4. Hook up the air pump (I use a small portable electric air pump/tire inflator that I bought at Walmart for about $15), and turn it on. The piston will push right out once the pressure builds up behind it.

I have used this method with consistently successful results.

AS FOR THE DUST BOOT, here is what I have done:

A. place the piston in the dust boot, with the outer surface facing the correct direction.

B. Stretch and slide the outer openning of the boot down over the piston (brake fluid as lube is good). This will result in the piston looking like it is wearing a rubber skirt.

C. Mount the inner edge of the dust boot into the caliper.

D. Push the piston into the caliper, smoothly gliding in past the inner edge of the dust boot seal, and the caliper seal ring.

E. As you do D, above, let the outer openning of the dust boot seal slide up the piston and into the groove on the piston.

For all of this, it is important to keep the parts clean, dust and grit free, and away from any contaminants.

Good luck. Let us know how you make out.

I pushed the piston in all the way then walked the seal in with two screw drivers. Push down on one, move the next right next to it and push down, move the first next to the second and so on.

Worked great.