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[Craig]

Sticking Disk Brake..

Right My RE disk Brake on my 2005 Model (in Daily use) Keeps sticking on due to the Crud/Salt?, or??, I have tried every thing, Cleaned pistons with brake fluid and next time with brake cleaner..Lubed with Brake fluid .Tried Silicon lube etc. New Pads, etc, etc, Even tried a Different caliper on it..

So every thing works fine just like new, but with in a day or Two it starts locking on again in use etc..(Tap it Free fine, but worse next time). Any one got any idea’s ..

Next step is to re-furb my old caliper with new piston and seals but it is not cheap if it locks up again :0(… SO:
Q: How do you get and keep a Free Moving Sweet Disk Brake. …Cheers. All.

[Haggis]

Are you still using the original rubber brake pipe? They can start to delaminate internally and cause a similar fault.

[papasmurf]

Have you put a light smear of copper slip, on the non brake material part of the pads. Where the pads slide in the caliper. A smear on the bit of the pistons exposed to the air does not hurt either.

[Craig]

Replaced all & greased all,,,but that pipe..New hose then?/ Thank;s Haggis

[AndyMc]

If you replace the pipe go for braided hose it makes a huge difference and change all the fluid in the master cylinder and caliper.

[stinkwheel]

The seals have been in there for 12 years now. There is probably a load of alloy corrosion in the grooves the seals sit in forcing the seal against the piston. Sometimes a seal gets twisted in its seat too.



You probably need to pump the pistons out, pry the old seals out, scrape/brush/wiggle the corrosion out of the seal lands, fit new seals and reassemble. You can put a tiny smear of red rubber grease behind and on the seals to facilitate reassembly and help prevent recurrance. WHile you're in there, give the pistons a clean and polish. If there's any significant pitting, replace it/them.



They can also get corrosion on the sliding pins making them stick. Particularly on the alloy between the calliper body and rubber seal on the side that's drilled all the way through. So much so as you often destroy the boot removing it. Again, pull the calliper off the pins, remove the boot (WD40 can help here)
and scrape/sand/wire wool the corrosion off the alloy. Re-fit with a new boot, again, use red rubber grease.



That's you spent about £15 on two seals, two dust seals, a rubber boot and a small container of red rubber grease off ebay.



While it's all apart, give the master cylinder a good clean out, particularly with reference to the tiny return pinhole which can prevent the piston depressurising after it is applied.



It's not a big or hard job. I've done it very recently.

[stinkwheel]

Hang on. I just saw you tried a new calliper. Teach me to read more carefully.



Almost certainly the master cylinder return hole's blocked. Unless both callipers are binding.



I'd strip the MC and see how it looks. You'll probably destroy the rubber boot over the plunger (if it's not already shot) and may land up wrecking the circlip so I'd have both on hand before you start. The piston assembly can be inspected (replaced if necessary) and the holes (feed and return) can be cleaned out with brake cleaner then compressed air or bunged through an ultrasonic then blown through. Doesn't take much to block them.



As above, refurbing a calliper isn't all that expensive. My prior estimate was a bit off. Pretty much bang on £20 delivered from our hosts for seals and boot.

[ric]

Had similar problem due to riding the bike in winter on salty roads. Salted water found its way beneath the piston seal and the resulting corrosion forced the seal hard against the piston. Only cure was to remove the piston and polish it clean and clear the seal groove completely. A dentists mirror comes in handy to check the front of the groove which you are unable to see. I used cocktail ticks and matchsticks to clean the groove without causing damage. A tooth brush and washing up liquid to clean the internals.

I cannot recall if the piston seal is lipped or not to confirm whether it's directional or not.

[Rattlebattle]

As you’ve already substituted a (presumably) known good caliper with the same results logic would suggest it’s something else. My money is on a partially collapsed rubber hose; this can definitely cause a blockage by tiny bits of rubber breaking away that leads to the pads appearing to stick. I always swap mine for braided, which apart from producing a more solid feel at the lever because it doesn’t expand also doesn’t degrade as quickly. The other possibility is that the master cylinder needs attention. Possibly the recovery port is partially blocked, leading to the same problem because the fluid cannot properly return when the lever is released. Good luck.

[Robin]

Hi Craig. I used to run into the same problem on my commuter Electra X every winter when the council started gritting. It's many years ago now, but I seem to recall that the front brake locked up on average about twice every winter. A partial disassemble and clean always got the stuck pistons sliding in and out again - for a while at least. On one occasion I even replaced the old pistons and seals, but don't recall that this actually helped in the long run. The fact that the front brake was trouble free for most of the year, and only started locking up once the gritting started, might point to a weakness in the design or manufacture of these brakes. Mine was manufactured by an Indian company from Kerala, if I remember correctly. Perhaps you have the same brake. I don't think I ever did replace the rubber hose with the braided version, but if you do, it may allow you to exert more pressure on the pistons, and keep them moving for longer before they..lock up. Good luck.