Avid Juicy Caliper Stuck

[AngoXC]

Woke up to a nice warm morning here in Melbourne so I decided to pull out my mountain bike which has remained dormant for most of the winter. I'd hardly reached the end of the street before I was slowed to a crawl - rear brake is almost fully locked

After taking off the back wheel, I've attempted to reset the pistons with little success - I'm guessing there may be too much fluid (or air?) in the system? May attack this later with a toothbrush in case there is a bit of rubbish in there jamming the pistons.

Any tips on how to rectify the issue? I've heard of people flicking the hose to cause any air bubbles to rise up to the reservoir, then, extracting this fluid using a syringe though the description I found was a little vague. (I'm also a little hesitant to do this as a past crash has damaged the bleed valve making its removal difficult- I'm aware this could result in a trip to the bike shop but if there are any suggestions that could prevent me making this trip, I'd love to hear them.

Brake is a Juicy Five by the way.

Cheers,
Gus

 

[T-Rex]

I reckon the most likely candidate is dirt or whatever jamming one or both pistons. Maybe start out by giving them a good clean out with BrakeKleen (Iospropyl alchhol) and a toothbrush.

You can force the pistons back by loosening the bleed valve on the lever and carefully twisting a large flat bladed screw driver between the pads (use an old set of pads as this will damage the friction material on a good set). Make sure you have a rag wrapped around the lever so you don't get brake fluid everywhere. If you are careful you can do this without needing to rebleed the system.

if you have to bleed them, you really need an Avid bleed kit, which is annoyingly expensive, but does work very well.

 

[gixer7]

I'll second T-Rex's analysis although I'd try and force the pistons back without loosening the bleed valve first - I've never had to loosen it and I always got them moving again. Less chance of letting air into the system by mistook.

I've found it easier to remove the break pads completely and insert the screwdriver and instead of twisting to force the pistons I pull on both ends of the screwdriver.

My Juicy's only have road duties but they seem to be the worst for build up of crap that blocks the pistons.

 

[AngoXC]

Cheers for the replies guys.

I had a good play around and got the pistons moving but as soon as I'd force one piston back into the caliper, the other would pop out - it's like whack a mole!

I'm thinking there is definitely too much pressure in the system but because I can't remove the bleed screw, I think it's going to remain like this for some time until I can get it down to the LBS.

 

[gixer7]

Interesting. So these brakes worked fine before?

Only thing I can think of is something has got into the system ie. moisture cause I can't think why else the pressure would increase. From memory I think Juicy's (maybe early versions only) did have problems with the seals but I could be wrong on that too.

If you feel like updating this thread if/when you get it diagnosed I'd be grateful at least to learn the cause.

 

[D_Nine]

Juicy's use DOT fluid,this is hygroscopic ie it atracts and absorbs moisture.If your bike has been idle for some time it is likely that the brakes have been slowly absorbing moisture.If you can't undo the top bleed screw you can try attacking it from the other end.Get a small container a bit of hose and a 6mm ring spaner.Attach the hose to the bleeder nipple put the other end in the container.Slowly undo the bleeder a small amount of fluid should escape into the hose.Lock of the bleeder this sholud releive some of the built up pressure.I had a brake that was'nt used fro a year and it was locked on solid! Ideally a bleed would be best but this should be a quick fix.Best of luck.

 

[AngoXC]

It's 2005 brake so a reasonably early model.

I actually had the same thing happen to me around the same time last year, though whilst trying to remove my rear wheel (which was clamped down in the caliper tight), I damaged the piston which called for a lengthy wait for some parts from the distributor.

It's funny though, as I was pushing the bike up the driveway, it was fine - 100mm down the street (flat), I couldn't coast without slowing down and at 200mm, I was having difficulty pedaling (all in the space of a minute or so).

I'm willing to bet moisture/air is the culprit, especially as it's more likely to expand with the temperature.

I'll attempt to relieve some pressure from the other end - hopefully there is still enough pressure to compress the pistons when the brake is cold!

(Like a rat deserting a sinking ship, I'm presently hunting for some Shimano brakes - an upgrade that's been a long time coming...)

 

[krisko]

Get the caliper serviced. You will need new caliper seals, refit and bleed.

If you leave it too long the caliper may seaze. The piston(s) will get permanently stuck down.

My Juicy Ultimates suffered this fate. I tried an air compressor with extremely high pressure to release the piston but it just didn't move.

Even a soak over night in WD then a re attempt didn't work!

Dirt and grit damage the seal, and or get trapped in between the piston and piston body trapping the piston.

 

[miko]

I had a similar problem recently with my girlfriends Juicys of the same vintage. I was able to use old pads and a flat screwdriver to get the pads apart. They seem OK now, although could definitely use a service. I've also had luck fixing sticky pistons by taking the pads out and squeezing the levers so a reasonable amount of the piston is exposed. Then I put a little brake fluid around the base of the exposed piston and pushed them back it. It seemed to free the piston up a bit. Careful you don't go too far though!

Nothing will beat a rebuild though. It's amazing how much crap will accumulate in the bore between the piston. It's quite a tight fit, so that isn't desirable.

 

[AngoXC]

In all honesty the piston seems fine - (I admit the thread title is now a little misleading) I think the main issue is a build up of pressure in they system. Without pads, pistons compress on the spacer (I've put in there temporarily) fine and reset with relative ease but only to a point, upon which the opposing piston starts to move. That said, I cannot dismiss any muck being trapped in there - they will see a service but in the mean time, I'm hoping relieving the pressure via the caliper may just tie me over.

It's wet/damp outside so I'm a little hesitant to start tinkering with them now (since I'm likely to introduce more moisture to the system) but when I do have a look, I'll let you all know.

Thanks for the help guys! Much appreciated!