front brake caliper

pcloudy · Posted: Fri Apr 24, 2009 12:25 pm Post subject: front brake caliper

So I had a stuck front brake caliper and got a used one off ebay that is apparently also stuck, is there anything you can do to unlock them or are they done once they have locked up. And is there anywhere to pick up a substitute other than ebay? thanks

fasterspider · Posted: Fri Apr 24, 2009 1:55 pm Post subject:

Use high pressure air or a grease gun to get the piston out, it will come out.

pcloudy · Posted: Fri Apr 24, 2009 1:59 pm Post subject: ...

Will that be worth it or will it never work the same after it locks up, I read that it will never seal properly after it locks up.

MR.CHocko · Posted: Fri Apr 24, 2009 2:13 pm Post subject:

IF you tell us the bike make and model I am sure someone would have one. You could try any of the links here for parts, also check out some of the salvage yards. A lot of us have a huge network of parts suppliers that we turn to before we even look at ebay.

KirkN · Posted: Fri Apr 24, 2009 2:15 pm Post subject:

Naaah, you've been misinformed. Smile

Any caliper can be rebuilt unless they're so corrosion-pitted in the bore that you don't bother. But, most of the time, a good cleaning and new seal, and yer good to go!

As for disassembly - what Ray said!

fasterspider · Posted: Fri Apr 24, 2009 2:51 pm Post subject: Re: ...

pcloudy · Posted: Fri Apr 24, 2009 2:59 pm Post subject: ...

I dont have it right in front of me but just for clarification how do I hook up high pressure air to it, will i need a specific adapter of some sort? thanks

KirkN · Posted: Fri Apr 24, 2009 4:04 pm Post subject:

Oh, you're in for a treat!

Use an air blower attachment with a rubber tip. GENTLY apply air at the removed bleeder screw port.

What will almost certainly happen is that it won't move won't move won't move BAM!! it'll blow out, spraying cruddy brake fluid all over your bench, and startling the beejeezus out of you.

Once your pulse settles back down, clean & refurbish as Ray describes.

Modify your own technique as you see fit... Very Happy

Bikegeezer · Posted: Fri Apr 24, 2009 4:25 pm Post subject:

And when you remove the seal from the bore, clean ALL of the crud out of the seal groove. If you leave any filth in there, the seal won't seat completely, and it'll apply too much pressure on the piston. That's likely what locked it up in the first place.

Stu

pcloudy · Posted: Fri Apr 24, 2009 8:25 pm Post subject:

Blue · Posted: Fri Apr 24, 2009 8:50 pm Post subject: air nozzles

Yeah, farm and fleet, lowes, harbor freight, do-it best hardware, etc. all should have them. Question is do you have enough compressor for the job, if not grease gun time, messy but effective. Blue

KirkN · Posted: Sat Apr 25, 2009 6:34 am Post subject:

What Blue said, as far as availability... Home Depot, too. Anyplace that sell air compressors and accessories.

As for compressor, it doesn't really need much 'guts' at all for it. Anything that will develop 80 or 90 psi will do. No real volume needed, since you're just pressurizing a tiny little space.

My favorite technique is to just barely crack open the valve, so that air just barely flows. Eventually, of course, in a dead-headed chamber (like a brake caliper) full pressure will develop, but it does it v e r r r y s l o w w w l y y, which gives you a better feel for when the piston is about to pop out.

Also, put a rag between the piston and the caliper to cushion the pop. And by all means, keep your fingers out of the line of fire! Smile

Others have advocated the grease gun method as being less traumatic - pump it up and out slides the caliper - no bother. I've just never done it, myself.

Have fun! Smile

pcloudy · Posted: Sat Apr 25, 2009 7:07 am Post subject: ...

I have access to a grease gun but have never used one, how should that hook up to the caliper?

Bikegeezer · Posted: Sat Apr 25, 2009 7:08 am Post subject:

pcloudy · Posted: Sun Apr 26, 2009 4:13 pm Post subject: ...

So I talked to the guy who has been working on the bike and he said he put 150psi into it and nothing, its locked up for good according to him.

Does anyone know if a 78 cb750 caliper assembly is compatible?