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Just went to sell my Avid brakes, was fitting pads and realised that one of the pistons won't retract fully.
A quick google search reveals lots of threads about how to unseize them, but none appear to end with a positive fix.
So have any of the experts on here actually had success fixing theirs, or are they now only fit for the bin?
I fixed plenty of recurrent Avid brake problems on customers bikes by throwing them in the bin and fitting hopes, on a more serious note they can be unseized quite easily but if the've stuck in the first place then deformation of the seal or piston is more likely and will need to be replaced, then thrown in the bin.
A full calliper service kit is as cheap as chips and includes replacement pistons and seals. A little creativity with a track pump to pop the pistons out and it's easy peasey.
I love my Avid Elixir R's and I own Hope brakes too.
I find that letting a bit of fluid out of the caliper whilst pushing the piston solves this easy peasy. You might want to bleed after, but I have not found this neccesary.
its not fully seized. It just won't retract far enough to get the pads in.
Not sure I trust myself with rebuild kits to be honest, especially given I was only looking to sell then on anyway.
edit - toys will give that a go. ta
Yup I only reccommended that cos you said it would only retract so far. The alternative is to use a big rubber band to hold the lever closed, I think this allows the fluid back up into the reservoir.
In reality I do not think this is a piston seizure issue, just a user failure to understand issue (not aimed at you OP, but at all the avid siezed piston chatter on the net). I think there is a gate on the avid lever that will not let fluid back in when the lever is closed. It makes sense, as the pad wears, the lever adds a bit more fluid to the system to take up pad wear, otherwise a ruddy great gap would open up between the pad and disc and then where would we be.
If you push the piston hard does the other piston move out a bit? If so, there's simply too much fluid in the system and you need to let a bit out.
The bleed procedure tells you to push as much fluid in as possible at the end, but if the pistons aren't fully retracted when you bleed it, you'll end up with too much fluid in the system, and you won't be able to retract them when you change pads.
Like all open systems, the lever closes off the reservoir when you pull on it, so the rubber band trick won't help here. That can help if the caliper seals are sticking and not allowing the pistons to "self-adjust" closer to the discs.
Had this last week. easy fix, cable tie the lever to the bar to put system under pressure, c
Slowly undo the bleed screw on the lever with an old rag to catch the fluid. Let a small bit out at a time until its enough to make the pistons retract.
Clean calliper n pistons thoroughly before fitting the new pads.
Hope this works for you