Forum menu
Ok, my bike is awaiting a warranty job via ATB at the moment so a friend kindly gave me one of his bikes to use until i get mine back, however on collection it appears there is a problem with the front Avid Juicy 5 brake.
Problem.....
Lever has nothing (i mean nothing) until it is right up against the grip , the brake works at that point only.
Pistons are not moving more than a mm or 2 under braking pressure.
What i have done to sort it....
Bled the brake (full bleed) 3 times. The old fluid was filthy black colour. Some lever feel came back at about halfway but weak.
Cleaned the pistons with fluid and tried to get to come out but no luck, they do push in ok though.
Tried leaving the lever pulled overnight. No difference today. The brake is back to nothing until up against the grip virtually.
So what next?.
Cleaned the pistons with fluid and tried to get to come out but no luck, they do push in ok though.
Can you go into a little more detail with this please.
If you remove the pads and then put a spanner over one of the pistons can you push the other out?
Does this work with both pistons individually?
If above works repete 4 or 5 times clening and lubing each time on each piston or untill they both move.
One other thing to check is that the pistons are square in the caliper. I have taped up the ends of a pair of needle nose pliers to gently grip the central knob on the piston to give it a wiggle.
If none of this works it is strip the claiper time and £10 for some new pistons and seals.
Have you bled them as per the SRAM/Avid video on youtube? If not...
And, IME Juicy's are a PITA once they get old/used.
Ok, Rusty.... I kept one piston in then actuated the brake lever nothing happened. Did the same with the other piston again nothing.
I have noticed that one piston has a chip in it at the outer edge though.
BR....yes i have followed the bleeding procedure , i have done Juicy's for years and Elixirs so hopefully i have been correct.
Sounds like both pistons are a bit stuck.
If you have the bleed kit you can put some fluid in one of the seringes and attach it directly to the caliper, that may hep in pushing the pistons out. What you are looking to do is get some fluid between the piston and the o-ring to lubricate things.
If they are totally stuck you may be abel to tweese them out (taped up needel nose pliers on the piston) a little while getting someone to pull on the lever. Once you get them moving it is a case repeteing the fluid on the piston to get them properly lubedricated.
If none of that works it is splitting the claiper and replacing the pistons.
Good luck
Update....
Managed to get both pistons moving in/out seperately but it takes a fair bit of lever pumping to move them, have cleaned and lubed them approx 6 times.
Completely bled the brake again (loads of black fluid came out again?) twice, lever feel was ok (bit soft) whilst bleeding but as soon as i re-assemble and pop wheel back in the lever feels rubbish again . The brakes do apply but only when the lever is near the grip. The pistons appear to not move very much when its all set up.
Driving me nuts now, could the pads be too worn down, they dont look excessively worn , getting close but not ott.
Is it an avid bleed kit or just a pair of syringes with suitable connections?
Sounds like you are descovering why peole have a love hate relationship with avid brakes.
You are making progress although it doesn't really seem like it.
2 final pointers
1 Really go to town on the saringe on the claiper at the beginning of the bleed process, pushing and pulling while tapping on the caliper (some of the nasty black fluid could be causing an obstruction between the two halfs of the caliper)
2 With the pistons now moving try the tie the lever to the bar trick again.
I would fill the lever syringe full and flush through until its looking clean. Do this top to bottom,lever to calliper,as the calliper end will no doubt be holding more crap so there's no point in flushing more of it up through the lever seals.
Once flushed through I would then half fill the syringes and start working back and forth to try and dislodge any dirt that could be blocking any of the ports.Don't bother de-gassing. It won't help what you are aiming for so it's a waste of time at this stage. Once everything is flowing freely and you have a good bit of pressure in there.. remove the pistons with the pressure you now have by pumping them out equally to enable easy removal.Split the calliper and clean the bores and lube the pistons with silicone lube.
Refit pistons and start bleeding. This might sound like a heap of extra work but in the long run,it's not. After messing around with quick-fix bleeds you soon learn to clean things out at the calliper to enable the best possible return of the pistons. Also remember to fully fit the pistons into the bores (don't start the bleed if they are at all proud) and block them off in that position with a block and some paper layered up to keep them hard into the bores. The avid bleed block allows the pistons to move slightly,I don't use them.
Worth buying a new seal for the calliper once you split it.
I take it that you've checked the position of the bite-point adjuster?
The pistons won't move very much when you pull the lever - probably just 1mm or so. What's supposed to happen is that when you pull the lever they move, and if they don't make contact with the disc straight away, then when you release the lever they don't retract quite to their original position, so if you pull the lever repeatedly the pistons will get closer and closer to the disc. This is how they self-adjust for pad and disc wear, and is why you have to pull the lever repeatedly if you retract the pistons manually.
There's really only two ways that this can go wrong:
1. The calipers stick to the seal so that they go back to their original position and don't creep inwards with each stroke.
2. Insufficient fluid is forced into the caliper. This could be air in the hose, or a failed seal in the caliper.
A final possibility is that there's not enough fluid in the system and your pads/disc are very worn. This is why the last stage of the bleed is to force fluid into the lever reservoir.
Take the brake off the wheel, retract the pistons, pull on the lever and watch what happens. Do the pistons start moving pretty much as soon as you pull on the lever, or only once the lever gets close to the bar? When you release the lever do the go back to exactly where they were before? If you pull repeatedly, do the pistons end up closer and closer together?
Ok.....
when i fully retract the pistons and pull the lever they both move straight away. Although the lever feels a little slack.
They do not fully return back to their original position, they do seem to move back a tiny amount.
If i pull repeatedly they move closer and closer together.
When i push pistons back manually they go in easy.
Update....
Just rebled following the exact video from Avid just to be 100%. The lever feels tonnes better now and actuates the brake after just a small pull of the lever. Its not firm but smooth and is fully on about 20mm away from the grips.
Going to leave it now until the morning and see if its still ok.
Thanks to all for your info/help. Cheers.
Great stuff, glad you got it fixed.
I'm sure your mate who lent you the bike will be over the moon to get his bike back in better condition than he lent it to you too.
Rusty....dont know about that , i've not ridden it yet 😀
Well test ride successful, brake working as it should and lever feels the same at end of the ride.
Cheers all.