Brake question

[JerseyJon]

Hey fellas. So I'm rebuilding my front calipers. The information on this site has been just exceptional. I have one quick question. I am replacing the four sided O ring back into the groove in the caliper. And it kind of looks like the O ring is not symmetrical. That is, it looks like it is slightly chamfered in One Direction. Could it be that there is a top and a bottom to this O-ring? Are my eyes deceiving me? Has this 37-year-old piece of rubber change shape from years of getting pulled in one direction? Again, I remain ever so grateful for the wisdom here, and the way it is shared.

[JerseyJon]

And while I'm at it,

And while I'm at it, how important is it to remove the spring clip that is wedged into the body of the caliper? It Doesn't look like a critical element in the rebuild process. But if you guys say it is, I'll do it right after I ask you how to do it.

[jetmechmarty]

Are you using new parts, or putting the old seal back in? The snap ring holds the dust boot in place. Do you have a dust boot?

A rebuild kit looks like this. Is this what you're doing?

I have always known the seal to be cut square. A rebuild means new parts. You should replace the seal and dust boot with new.

[JerseyJon]

Thanks Marty. No, I am using the old dust boot, and the old square ring. The piston looks really good, the dust booth in the ring both look good, and the caliper was not leaking. It was just dragging a little.

Another issue is the trickiness of getting the square o-ring back into the groove. Seems easy enough, but, frankly, getting the piston out with the grease gun method was a lot easier than trying to get that elusive rubbery O ring back into that groove. if anyone has any brilliant ideas on how to accomplish that, I'm all ears.

[DiverRay]

First off, you DID clean the grove REALLY WELL, correct? If so, then on to the install.
1. Put some NEW brake fluid on your fingers and work it all over the square seal.
2. Start with one side of the seal, pushed into the caliper in an oval shape.
3. start with the part that is nearest the grove, and use two fingers to push it in.
4. using the same two fingers, work the o ring into the grove, going the opposite directions around the inside of the caliper.
5. When it's almost all the way in, push the last bit in with one or two fingers, keeping the o ring square in the grove as you work it in.
Hope this helps!
Oh, IF you used brake clean on the rubber, its done! you will need to buy a new seal.

[donebysunday]

Thanks Marty. No, I am using the old dust boot, and the old square ring. The piston looks really good, the dust booth in the ring both look good, and the caliper was not leaking. It was just dragging a little.

Another issue is the trickiness of getting the square o-ring back into the groove. Seems easy enough, but, frankly, getting the piston out with the grease gun method was a lot easier than trying to get that elusive rubbery O ring back into that groove. if anyone has any brilliant ideas on how to accomplish that, I'm all ears.

I've never done this this way but I think I heard of using a radiator hose clamp to compress the O-ring just a bit, with brake fluid as a lubricant to push it back into the caliper, anyone done this ?

[JerseyJon]

Hey Ray

Thanks for that nicely described o-ring insertion procedure. Yes, I used PJ1 super cleaner on all of the parts. Rubber and metal.

[JerseyJon]

Sooo....

Following Ray's procedure, I was able to get the ring back in the groove. Thanks again, Ray. But getting the piston back in is a difficult matter. Compress it in with a C clamp?

[HalfCentury]

I used a drill press

Chuck a ratchet extension. Use round end of the extension to push the piston into the caliper. Make sure to lube everything with brake fluid.

You have to tilt the caliper to make the piston want to go straight down.

[JerseyJon]

Thank you HC. I ended up using an old Jorgensen clip it push the piston back into the caliber a half a turn at a time. Doing the second caliber now. Will report tomorrow is to leaks and stopping. Thank you all again.

[DiverRay]

If it's that hard to push in with no hose on it, you probably do not have the grove cleaned as well as you should. It's aluminum and when that oxidizes the results are used for sand paper! I've bent a cheap flat blade screw driver that has been ground to match the grove to clean them out. Even with that, it takes me about 20 minutes on one that's not too bad, and 40 minutes for a really bad caliper.

[JerseyJon]

I woke up thinking the same thing, Ray. Something is amiss.

The reason I rebuilt the calipers in the first place is because one of them was sticking. I started with the left one. I re-used the old square o-ring and dust cover, but I cleaned all the rubber parts with brake cleaner spray. That may have been a mistake. When I put it back together, I struggled to get the o-ring seated in the groove. I got it though, and then REALLY struggled to get the piston back in the bore. In the end, I used a Jorgensen Clamp to push it back in, by tightening it a quarter turn at a time. This is foreshadowing.

The right side caliper went much more smoothly. First, I didn't us brake parts cleaner spray on the rubber parts, including the o-ring. Then, when I got it all back together, I was able to push the piston into the bore by hand.

Now, why would I think that that left side caliper, the one that I had to use so much force to push the piston back into the bore, would not stick when I put it back on the bike? I'm going to remount the calipers and see what happens, but I'm not hopeful.

I ordered a rebuild kit from mikesxs, and will put in a new o-ring and dust cover when it arrives.