Avid Juicy piston stuck / caliper service

mr mangos

It had to happen. After all my harping on about how great my Juicy threes are, I think I have a problem.

One of the pistons on the front is not retracting fully. It's sitting maybe a couple of millimetres out. Not much but enough that when the brake is at rest, the rotor is centred between the pads but not centred in the gap between the calipers. The rotor is nearly touching the caliper casing now. I've tried pushing the piston back as hard as I dare but it won't shift. It's not causing any functional problem really, but it's bugging the hell out of me because I know it's not right. I can't be sure they weren't like this since I got them. Could it be caused by too much fluid? But then I suppose both pistons would be stuck out.

I've checked the service manual for the caliper service instructions which seem straight forward enough, and I'm guessing they'll need a bleed once it's done.

I could send them back I suppose but I'd rather learn how to do it and avoid the wait. Has anyone done the service? Are there any pitfalls to watch out for?

tmg

My front ultimate had to be sent in to Avid to have theseals replaced, took them over two weeks to do it, LBS called them a few times to be told it was on the bench and would be done that day and it wasn't, my adivce would be avoid sending it back, if you cant do it see if your LBS can. If you do end up sending it in make sure you keep on at them to get it done

mr mangos

I should clarify I'm looking for feedback on doing the caliper service myself. I don't think I'll be sending them off. If it comes down to it I'd rather drop £50 on a new brake and get it next day.

ratty2k

When I had car calipers stick out, its usually 'cause the seals have dried out. Take the pads out, and carefully put a small amount of brakefluid on the piston thats sticking out, and then just (Carefully again) work the piston in and out a few times.
Mind you, most pistons will stick a bit, and I dont really see it as anything to worry about, you'll get slightly uneven pad wear, and thats it.

mr mangos

Update on this. Turns out the piston was only stuck out because that's where it 'auto-adjusted' to. The real problem is the OTHER piston!

I pushed both pistons back flush with the caliper. When I pull the lever one piston moves more than the other, so when both pads hit the rotor they are not centred in the caliper.

I tried servicing the caliper as best I could but I don't have an air compressor which you apparently need to get the pistons out.

I got on to the shop I bought them from but they're saying that I need to pay them for a service. My view is that the brakes have only done about 350 miles and this should be covered under warranty.

Do Juicys need such frequent servicing? Nothing in the manual about it.

stumpyjon

My Juicy 7's have done about 450 miles this year and I've had no problems like you've described, only just vaguely considering new pads in the rear.

I thought bar the odd bleed Avid Juicys were supposed to be fit and forget (within reason).

RIKO

I've recently serviced my hope mini's and you don't need an air compressor to get pistons out you just need a bike pump just be careful as air is more explosive than oil when released under pressure and they do fly out at quite a rapid rate!

mr mangos

Yeah I tried my bike pump but they wouldn't budge. As I can't complete the service I've ended up sending them off so we'll see what happens.

ddraver

my LBS used GT85 on mine and they were fine (but people have said the seal expand so be careful - yes they are a good LBS!!!)

take out all the braking surfaces/pads/disks etc, soak the piston in either one and just push the piston back in (very carefully the first time, i think i cracked the caliper doing it) and then push it out with the brake lever and work it back and ofrth over and over (its boring) untill when you squeeze the lever both pistons move equally

if they re really dead you can get new pistons from CRC for naff all, and i think fitting is pretty simple tbh (not done it personally)

clean everything off really well and replace all the bits et voila...

I'm pretty sure it was just travelling home for Xmas with all the road salt spray that did mine .....

Jonr

mr mangos wrote:

Update on this. Turns out the piston was only stuck out because that's where it 'auto-adjusted' to. The real problem is the OTHER piston!

I pushed both pistons back flush with the caliper. When I pull the lever one piston moves more than the other, so when both pads hit the rotor they are not centred in the caliper.

I tried servicing the caliper as best I could but I don't have an air compressor which you apparently need to get the pistons out.

I got on to the shop I bought them from but they're saying that I need to pay them for a service. My view is that the brakes have only done about 350 miles and this should be covered under warranty.

Do Juicys need such frequent servicing? Nothing in the manual about it.

You can push the piston out using your brake lever; remove the caliper from its fixing, clamp the none seized piston in as far as you can (I used two small spanners, one of which needs to fit through the caliper, and a couple of small clamps). Then pump the brake lever several times and the piston will come out just beyond the seal. Then dismantle the caliper and pull the said piston out by hand. I would only recommend this if you are replacing the piston seal, or at least that's what I did. If you need to to remove both pistons you'll have to remove each piston separately reassembling, bleeding and then dismantling again in between which makes it a hassle to do two at once but usually only one would seize at once unless your unlucky.

Always try to get the piston moving back and forth first using the method described in a previous post first as this is easier - doesn't require dismantling or bleeding. There is a technical manual available on the net somewhere that I found:

http://www.cycleslambert.com/download.p ... Manual.pdf

My experience is that they do need a bit of maintenance if you ride mainly off road where its wet and muddy. I had one piston seize in the same way as you describe over the course of about 250 miles but I guess I could have cleaned them better/ more regularly. As a last resort I renewed the piston seal.

mr mangos

This is doing my nut in. Got the brake back today and it's the same! Both pistons move but the outboard piston only moves a fraction as much as the inboard one. Plus the beautifully bled brake I sent away is now a spongy mess.

Frustrating.

mamoo

This is not advice for the original poster as I'm sure you've sorted it now after all these years!

I had a similar problem after changing the pads and leaving it in the shed for about a year, pads wouldn't retract and were sticky, discs rubbed and pads wouldn't move equally. As others like myself search forums to cure snags I thought I'd post what I did:

I took the pads out and with a big flat blade screwdriver pushed one piston fully back in caliper, whilst holding it back, squeeze lever carefully so the other piston comes out, not too much but enough to put a smear of vaseline on it. Then push this back in with screw driver and hold the other one back again and cycle the vaselined one in and out with the lever and screw driver a few times. repeat on other piston.
Then put pads back in and I got a wooden clothes peg from the washing line, took it apart and you have 2 wedge shaped bits of wood, stick one straight down between the pads and one in from the side between the pads so they are spread equally and square and the wedge doesn't tilt the pads.
So 2 wedges in each brake, leave overnight.
Next day remove wedges, put wheels on, squeeze levers quickly 5-6 times then hold, go riding and eat cake.
Worked a treat.