Brake Calipers...

Hello, Both of my front brake calipers seem to be sticking on but not enough to lock the wheel. Should this just be a simple matter of disassembling and replacing the piston seals? The brake fluid seems ok, the pads are not abnormally worn and the lever seems ok... Any help would be appreciated. Thank you.

 

...Wondering if I can do the same as the similar topic reply (Brake Calipers Stuck On...) and use a c-clamp to compress the pistons back. I previously locked the front brakes on moving it off a trailer from storage...

 

Nope. In your case it sounds like the square seals may be overly dirty or worn. The seals that prevent the brake fluid from escaping the caliper are square (hense the name) and are intricate in the function of the brake calipers. When you apply the brake, the square seals deform as the piston moves towards the pads and at a point slip some to accomodate pad wear. When you release the lever, the square seals pull the pad(s) back away from the rotors so they don't drag. I suspect that yours may not be effective any longer (they are 20+ years old).

Brake fluid over time does evaporate some and turn into a gel so that may be some of your troubles. Brake fluid really should be changed at least every-other year due to its hydrophillic properties (loves water).

On another note, if they "seem" to be sticking when you rotate the wheel by hand, it may be the wheel bearings being set too tight or worn. Just another area to check out.

 

I had the exact same problem when I let my bike sit too long. Just disassemble the calipers and clean all the parts. You are basically performing an overhaul, but you shouldn't need new parts unless you rip or break the seals when you are taking them out.

The C-Clamp won't do you any good, because your brakes are actually sticking. In the other thread, the person had simply pumped the brakes so the pads were touching face to face with no rotor in between. The goal was simply to get a gap back between the brake pads, so he could re-install his front tire.

 

Thank you very much.

 

Re: Brake Caliper Question...

...I have removed both calipers and inspected them briefly and noticed there are no rubber seals on either piston at the brake pad side, should there be? Also the pistons seem to face the brake pads hollow side out? Hopefully not a stupid question but can't make sense sometimes of the Haynes manual. I want to rebuild the calipers due to hanging up... Thanks.

TD

 

No gasket between piston and pad, this is normal. Hollow side out aye, no worries there.

 

The hollow side out reduces the amount of brake fluid exposed to the high temperatures of the friction material during braking which is typical design theory. The square seals are on the inside the calipers which seal the piston in the bore and there should be two of them for each piston. You have to pull out the pistons to get to the seals.

 

Thank you both very much. Weekend project... Anyone have any "easy" solutions for bleeding the caliper/anti-dive? Looks like 2 bleeder valves on the anti-dive units, can I get away with just using that anti-dive to bleed the system?

 

The upper caliper bleeders are to allow removal of air trapped in the high points of the caliper. You should bleed them as well as the anti-dive units any time you crack open the system.

 

Thanks Robert I will.

 

I have a similar problem with front brake calipers on my '83 750 seca. One piston appears stuck in the caliper body. Is it appropriate to remove the one caliper from the fork and use the brake hydraulic pressure to force the piston out? It expect it to make a mess, so I plan to wrap the caliper in a plastic bag before applying the pressure. I believe that once the piston is out, I can clean the piston, caliper and seals to remove any smoot. Does this seem reasonable or is there a better way to get the piston out?

 

That's perfectly fine - works everytime for me with a minimum of fuss.

 

Thanks,
I'll try it tonight.

 

Xtown, you are using a very good method to remove the piston. Just be sure to place a block of wood in the pad harp to catch the ejecting piston or it could pop right through your plastic bag and hurt you!

 

Holy! I got the pistons out with air pressure, good thing I used the wood technique Robert... They are like bullets!!! It worked fine and now I can properly rebuild. Not looking forward to bleeding so may be back with some q&a later...

TD

 

This should be the ideal time for me to take care of my brakes, but the po stripped one of the screw heads on the reservoir.

 

Hmmm I am having a similar issue with one of the bleeder screws; must extract and replace shoudn't be too bad though...

 

Paul, you can get a nifty screw extractor from Sears. They work like a screwdriver tip and really dig those stripped screws out. Not too expensive either.

 

The Brake caliper piston was really stuck in the housing and required squeezing the brake lever with both hands (maybe I'm a wimp) but when it started moving it eased slowly out of the caliper. Now that it's out and after removing the rubber seals, I have all this amber colored yuk stuck to the inside of the piston housing. Anyone got an easy way of cleaning that stuff out? It feels like the housing is aluminum so I hate to use a steel wire brush/Dremel tool on it. Maybe a brass wire brush?