Avid Help

trail jacker

Hi All,

I have a set of Juicy 5's on my bike and they have been going strong for around 3/4 years.

However recently I have noticed that the pistons are not retracting properly so the pads are constantly touching the rotors. I am guessing that the calpiers have become full of dust etc over the 3ish years of use and it has built up and is blocking the path of the pistons (or inhibiting it).

What would be the best course of action to rectify them? I am going to take my bike to the lbs for a caliper overhaul on payday, but until then is there a quick fix?

Also... the rear brake vibrates loudly when I brake, and sends vibrations through the whole frame, any ideas what the cause could be or how I could fix it?

Sorry for the mammoth post!

Cheers!

ricardo_smooth

Check rotor/caliper bolts for the vibration. As for the calipers, take the pads out, drop a touch of brake fluid on the piston edges, push back, pump lever, ad fluid again and do this a few times and it may free the pistons off a bit more

trail jacker

something like this? http://www.chainreactioncycles.com/Mode ... elID=29900

I have checked the rotor and caliper bolts and everything is tight and in-line, thats whats confusing me as to the source of the vibration...

ricardo_smooth

Yes but car dot 4 or 5.1 brake fluid I the same and half the price so just use that.

diy

Those instructions might leave the OP with his pistons popped out..

Are you really suggesting the OP remove his pads and pulls the lever? If you don't have brake fluid already then isopropyl, brake cleaner or even some copper slip will do.

You should think about a full bleed and fluid replacement.

andrewjoseph

There is a possibility that a piston has corroded and may need replacing.

the only way to be sure is to take it all apart.

trail jacker

I think its more likely that the piston has corroded, had a look and it isn't looking too happy, and the movement of one of the pistons is very limited on both front and rear brakes.
Worth buying a new set? Or getting new pistons?

andrewjoseph

try getting new pistons, phenolic help with temperature management and also (I think) are restiant/impervious to corrosion.

Cheaper to replace pistons than get new brakes. would be worth getting new seals too.

ricardo_smooth

diy wrote:

Those instructions might leave the OP with his pistons popped out..

Are you really suggesting the OP remove his pads and pulls the lever? If you don't have brake fluid already then isopropyl, brake cleaner or even some copper slip will do.

You should think about a full bleed and fluid replacement.

They might pop out yes. A risk of servicing brakes.

Was unaware that iso alcohol could lubricate a sticky piston though so I've learned something new today 8)

trail jacker

so should I take the pads out, squeeze the lever slightly to expose some piston body, apply the iso alcohol then push back and repeat?

ricardo_smooth

yes, don't go mad with how far you push out the pistons and you should be fine

trail jacker

sweet, thanks for your help

trail jacker

could i use white spirit instead?

nicklouse

no.

andrewjoseph

I'm not sure how iso alcohol can help a stuck piston. Wouldn't it evaporate too quickly to do any good? it's not a lube and what would it do for corrosion?

trail jacker

I dont know, I dont have any so just going to spray some muc off into the calliper and move the piston around to see if that helps!

diy

Lets be clear about the advice here:

1. Need to clean the brake of all the crud. Brake cleaner (which is mostly alcohol) sprayed in to loosen all the crud and then brushed out will clean the brake. The fact that it will evaporate is a positive.

2. We don't know if these brakes have ever been bled or had the fluid replaced. Spongy brakes wont retract, so that needs checking.

3. The brake pistons might needs some lube. But 1 & 2 might do it anyway. If they do need lubing, brake fluid, copper slip, chain lube, teflon spray etc.. may all help provided they are used in very small quantities. Very much a wipe on wipe off.

Nobody should be considering replacing the brakes without doing the above

trail jacker

Sweet, it has been a while since the last bleed, so I will bleed them prior to fiddling with the pistons and see if it makes them retract better / fully. Cheers for the advice!