Avis Elixir 5s… After about 4 years of trouble free braking I thought I had some sticky pistons so advanced them and gave them a clean and bled the brake but the pistons still aren’t returning correctly and are dragging. It seems like when the lever is released it is sucking in air rather than pulling fluid back from the caliper, is this possible/likely with perhaps a damaged seal? I might be imagining it but I think I can hear a kind of sucking as the lever is released.
Does this sound feasible? And if so any advice on correcting it?
Cheers, Matt

Most likely cause of the noise is that the bladder in the lever is leaking. Lever rebuild kit should sort it. Also worth freeing the pistons up by pumping them out as far as you dare, scrub with a tooth brush, drop a little brake fluid on them push them back in, pump them out again, drop on a little more fluid if needed them push in and pump out, wiping off any crap until they both more freely and evenly.

Yep, the pistons are nice and clean/lubed and advance out easily and evenly. Think I might need a lever service kit…

It often isn’t obvious as you don’t get fluid leaking out but you can’t get them working right if it’s leaking in there. You’ll obviously need a full, careful bleed after.

Had the same thing with mine, unfortunately I sold them both for spares and bought some deores for £65 for the pair (CRC + voucher). I figured by the time I’d spent the cost of brake fluid and lever rebuild kits I wouldn’t be short of the cost of the deores, and as mine were old thought something else was bound to go wrong soon!
I don’t like them as much as the avids, but just couldnt be bothered any more!

I found leaving them upright hanging from a door for a few days really helped with the bleed though, and spending a good amount of time degassing the dot fluid before rather than just doing it quickly made a massive difference.

If you got a bleed kit, bleed them first – might sort it, especially if there’s no evidence of leaking fluid