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Hello all..

i noticed my rear brake was making a nasty noise this arvo,so i took out the pads to take a look..
i noticed that one pad had worn down loads more than the other..so i fitted new pads and saw that when centring the caliper with the lever, one piston comes out first and stays out more than the other..this happens on and off the bike..im wondering if i should strip down the caliper and take a look or just leave it well alone..i have never taken 1 apart before,but im dying to attack them hex bolts..whadda recon..its a deore lx585 caliper..thanks for any advice..Z

I'd go for it.. strip it down, clean it up, maybe replace the seals, make sure the pistons move freely and job done..

Should also mention that I've never done it either, so i could be talking rubbish! I'd be itching to get it to bits though!!

You could also try to clean it up a bit while assembled by moving the piston in and out a few times.. no idea how well that will work though.

PS: If it all goes wrong, please don't take me out to a quiet spot in the woods!

The cause is usually that on one side the seal is a bit dry or gritty. However, the seals in the the shimano callipers are not serviceable/replaceable as far as I know. You're best best is to give the whole calliper a good clean up with soap and water or isoproply alcohol. Then squeeze the pistons out (no so far that they pop out of the calliper, but almost) and coat them in mineral oil. Then push them back in and see if they start to push out equally.

If that doesn't help then you'd need to get a new calliper - might be tricky as those LX ones are getting on bit although any deore or XT ones from the same year should be interchangeable.

Yep sticky piston I had this There a thread also YouTube sticky piston.

Take pads out hold in moving piston with screwdriver squeeze lever slowly to pump none moving.

Slowly so cap don't pop out as break fluid run every were.

As above clean round piston.

Thanks all..have done all u suggested and cleaned with isopropyl, but 1 piston is still slow..fear that if i take it apart and any O rings have gone that ill never be able to replace them,like phinw said..might just live with it for a while..ta..Z

It's the dousing with mineral oil (best use the proper shimano stuff) bit that is important, as its likely a dry seal that's causing the stickiness. If you've not tried that too, give it a whirl.

As a last resort you can pop the pistons right out and try cleaning the seal but that will mean the brake will need refiling and bleeding afterward.

Donor parts on ebay here: http://www.ebay.co.uk/itm/Shimano-Deore-LX-BL-M585-disc-brakes-F-R-/330794796662?pt=UK_sportsleisure_cycling_bikeparts_SR&hash=item4d04e80676#ht_2156wt_1186

Thanks mate..have just tried with the oil but to no avail..think im gonna do what u suggest and pop out the piston and clean n re-grease..will do it next wk though when its raining!!..thanks for the link..didnt think of that..Z

Thought one side was supposed to move more than the other, same with all disk brakes, they should be aligned so that one pad makes contact first slightly gentler than when the other side comes crashing into it, this allows you to feather your brakes etc rather than just having an on/off effect

In theory the calliper should be aligned centrally on the disk and both pads should hit the disc equally. If not, the disc gets deflected and potentially warped and the pads will wear unequally. (Well, that is generally the case for most opposed 2 or 4 pot designs, on mechanical discs and some odd single piston brakes only one side is actuated, so one pad hits the brake before the other but those are the exception these days).

The feathering is just a function of the pressure in the calliper. Some designs have more modulation than others. Shimano owners ride the Avid brakes and complain they are spongy and need bleeding! Conversely Avid owners on Shimano brakes say they are "wooden" and feel "on/off ". Depends what you like!