UKC

sorry, another workshop question.
I'm about to give my bike the tlc it needs and had some great answers on here already for BB.
quite happy to do most maintenance on my bike, but have only ever bled my brakes, and i'm not convinced i did a great job either.

anyway the situation now is the one of the rear pistons doesn't seem keen on retracting properly.
it might just be too much fluid in the system, it might be something more serious.
they are Avid Elixir R SL hydraulics (according to the review from 2010 i managed to dig up on another site)
with the pads in place there isn't room to get the rotor in so the back wheel can't fit on the bike.
is it likely that i've ...
a) wreaked it... so it's time to buy either a new caliper or (not that i can afford it it) a new brake set
b) it could be fixed by loosening up the bleed valve and letting excess fluid out before gently squeezing with a g-clamp (i know not to knock lumps out of it with a hammer) or some other magic trick
c) its probably time to order a caliper rebuild kit for it... and if so where do i get one from? probably have to order it i expect?
d) something dead obvious i haven't thought of, but one of you wonderful people can suggest.

i'm happy to have a go at it, if i can find some decent instructions, but if it's a shop job then so be it.

(i should mention i have the avid bleed kit if that makes a difference)

In reply to rallymania:

I'm not sure whether avids needs more servicing than other brands, but I've find it's quite easy to do.

Sounds like the pistons have got dirty - you've probably done what I've done a few times and left them with old pads in for too long, so the pistons are exposed. Might be worth getting new pistons as it doesnt seem possible to get them properly clean.

With elixirs it quite easy to take the calipers apart - 2 bolts holding the two halves together, and with a bit of thought you can clamp one side and push the other piston out by applying the brake. Clean it up, apply some silicone spray if you have some, push back in place and bleed. Still sticking, time for new pistons.

This place seems good for all sorts of parts http://www.singletrackbikes.co.uk/ but I think there's little saving in a new caliper than a full unit.

In reply to rallymania:

Before you spend any money at all on these avids, shimano SLX brakes, bred and ready to use are only £49.99 on CRC at the moment.
My experience of avid brakes has been universally bad, they don't work very well for a start and they require silly amounts of maintenance to keep them running at all.
Shimano on the other hand have been great, they work well and require minimal maintenance.

In reply to gethin_allen:

I've read recent reviews which basically say that after a period of unreliability, Avid have now got things cracked for their hydraulic brakes, with them being reliable and effective/user friendly now.

In reply to rallymania:

I doubt if you've wrecked it. I've had similar problems with Avid Elixirs - I replaced worn pads with new, then couldn't get the rotor in the gap. The problem is the brake fluid absorbs water over time (increases volume and fluid becomes spongy). I bought the avid bleed kit and bled the brakes. It took a few goes and a bit of wasted fluid as the avid bleed kit is really rubbish - very hard to keep air out of the system. (the 'pro' bleed kit isn't much better than the basic version either). So a quick solution would be to get a decent bike shop to do it for you (or persevere and swear a lot like I do).

In reply to Timmd:


About time too.

Unfortunately for them I have no intention of ever buying them again and I know a good few others that have similar views.

In reply to rallymania:

Every set of Avids I've had ended up with sticky pistons. Moved to Shimano and not had a problem since. Started with XT then worked my way down to Deore after realising how little difference there is/how good Deore brakes are.

In reply to rallymania:

Sounds like you didn't push the piston back in before you bled it. You also need to put a spacer in the calliper to stop it pushing out when you put pressure on and slowly let the lever out. Filling the master cylinder.

If you let them go out too far you need to push em back in and bleed again. The piston will go out so far and not go back to centre it around the disk. It looks like they are sticking but you've let them go out too far.

On the other hand they are acting like avids and the service kit you are looking for is called shimano deor.

In reply to gethin_allen:



I've read glowing reviews, but fair enough.

In reply to gethin_allen:



Not been doing much mtb of late but agree entirely , £50 for new ones is money well spent . If they go wrong shimano will sort them out or replace them . Endless dickering about with avids just a complete pita .

In reply to Timmd:

You mean that after being on the market for 12 years they've finally worked out how to keep fluid in and air out? Reviews are only ever in the short term (I used to write a lot of them), and SRAM are very good at saying 'we've fixed the issues' every single year or new product release. I sacked SRAM off years ago, which is a shame as the guys are great to deal with, but the quality of many of their products is poor. That said, for the sake of balance, while I like Shimano I've also seen some real issues in their XTR levers recently where they either come back to the bar or just lock solid. No company is infallible but SRAM really do seem to be poorer than average despite higher than average prices, bouyed no doubt by the inflated RRP and low OEM costs (so their stuff is specced on high end bikes, helping with the halo effect).

OP. Given a seal kit is going to run you at least £15, I'd sersiously consider looking at the Shimano SLX if they're only £50 a set on CRC right now. The alternative would be to pop the caliper pistons out and polish up the pistons to clear any crap off them with something like t-cut or a mildly abrasive bathroom cleaner. Wipe the pistons down with either brake fluid or IPA and re-insert the pistons. If you do this though, first bleed the brakes from the top down before going through the usual bottom up bleed. This way you're not sucking a bunch of air through the lever which can lead to air being trapped in the little nooks in the M/C.