Avid Jucy 3 piston movement issues

j_l

Just a quick one, piston movement is un even so one piston retracts ok the one on the other side only retracts a tiny amount (less than 0.5mm) and the disk chatters / rubs against it, is this normal or does it need a rebuild?

They work really well and have loads of feel and power its just the uneven piston movement causes uneven pad wear and however may times I re centre the calliper the disk always slightly rubs- both front and rear.

any pointers welcome.

thanks in advance.

Jon

maringirl

Typical Avid - best to fit new seals

mrmonkfinger

more like, typical brakes, as it happens to all of them

try cleaning the pistons first - easy 5 minute job

remove wheel
hold the working piston stationary and work the lever to extend the non-working piston a bit (like 5mm)
use a rag with a drop of brake fluid (and only brake fluid, dot 4 or dot 5.1), wipe the side of the piston clean
push piston back in
repeat for other piston, while you're there

if that fails, then its probably time for new piston seals.

joshlg103

sounds like the rotor is still not centred properly but could be sticky or dirty pistons. avid brakes come apart easy and there's no need to release any fluid. the brake should have bolts that hold the two sides together that when undone releases the brake into two halves. the pistons can then be pushed/pulled out and the seals cleaned.

Dave_P1

joshlg103 wrote:

sounds like the rotor is still not centred properly but could be sticky or dirty pistons. avid brakes come apart easy and there's no need to release any fluid. the brake should have bolts that hold the two sides together that when undone releases the brake into two halves. the pistons can then be pushed/pulled out and the seals cleaned.

I always thought the brake fluid would leak out when splitting the caliper or do they not work like that?

cooldad

Dave_P1 wrote:

joshlg103 wrote:

sounds like the rotor is still not centred properly but could be sticky or dirty pistons. avid brakes come apart easy and there's no need to release any fluid. the brake should have bolts that hold the two sides together that when undone releases the brake into two halves. the pistons can then be pushed/pulled out and the seals cleaned.

I always thought the brake fluid would leak out when splitting the caliper or do they not work like that?

It will, all over the place.

joshlg103

the fluid won't leak out if u remove the hose from the caliper first. the fluid won't run freely out the hose unless you pull the brake lever.

mrmonkfinger

You don't need to mess about pulling the calliper apart to clean the pistons.

maringirl

We see Avids with this problem all the time. In most cases if we simply clean them out then they come back a few weeks later with same problem. It is easier to split the caliper clean everything fit new seals and pistons and o-ring(all come in same kit) bleed them and they will be nice and sweet.

mrmonkfinger

Yeah but no but, cleaning takes about 5 minutes and costs nothing.

Replacing pistons & seals is about £10 in parts, plus the time to strip & reassemble & bleed, assuming you don't pay a shop to do it, and you have a bleed kit already.