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I am trying to sort out the brakes on my wife's hardtail but have exhausted my knowledge. She hadn't used the bike for a while (a good few months) and the brakes were not performing as they should. The front was ok, not as good as it used to be; but the back had no power (won't even lock the wheel) and squeals badly.
Firstly I tried changing the pads and cleaning the rotors, then bedding the pads in. The brakes still felt the same. So I got a rotor I know is good and put it on the rear wheel, still no power. I then got the bleed kit out and bled the brakes (I last bled them in about August last year). The colour of the fluid was slightly grey but not as grey as I have seen it in the past. Brakes bled, pads and rotor's cleaned again and I took the bike out and tried to bed the pads in again. It felt exactly the same, no power on the rear, the front feeling ok but noticeably weaker than my XT brakes (same sized rotor).
Any other idea's of what I cant try? Or does it sound like the brakes have gone (bought them new when we got the bike just over 2 years ago).
No power & squeals = contaminated pads, either from leaking seals in which case new caliper is required or from some other contamination in which case cleaning of pads & disc plus heating pads is needed to burn off residual contamination - or replace with new pads
Sounds like leak from the seal. I tried everything but in the end stumped up the £25 ish for a new calliper (which also comes with pads which are £20 anyway)
What tools do you need and how difficult is changing the caliper?
Any good YouTube videos?
Thanks.
If I recall It's just a nut to undo and pull out the hose from the calliper, reattach and rebleed. You may have to stick in a new olive and insert too at the hose end if it leaks around the nut but I got away with that. Plenty of on line instructions for that (see shortening brake hose) and using a vice and shimano yellow block thing makes tapping in the insert easier.
Cheers for the suggestions, I will take a closer look at the calipers. Didn't immediately notice anything yesterday, but the bike was muddy and I didn't have much light when bleeding.
Which Deore model is it?
I might have a new caliper if you need one.
No power & squeals = contaminated pads
This. Go and find a big hill and repeatedly get up to speed and then brake almost to a stop. It may take a while, but you'll probably find that the power suddenly comes back once they get hot enough, but if the caliper is leaking, the problem will come back.
Which Deore model is it?
I might have a new caliper if you need one.
It's a M615. I've not managed to have a look, might get to tomorrow when I can get the bike out in the day light.
Model does not really matter as you can mix and match. I run deore calipers with xt levers, slx with alivio calipers (cheap as chips and basically the same as lower level deore).
Only difference is some use a banjo bolt (newer slx, xt and saint) so just make sure whatever you get has a threaded straight hose to mate with existing hose.
Infact I have just installed a £12.99 alivio caliper on my cx hydro rs685 levers and they are just as powerful as the m785s the bike originally came with (at a third the price).
A lot of shimano stuff is interchangeable through the various levels (the higher you get, the lighter things get with an exponential rise in cost and corresponding decrease in reliability IMHO) - that's why I tend to stick with the lower groupsets now.
doncorleoni, where did you get your Alivio calliper for 12.99 please? At that price I’d give changing one a try.
I got it from bikster.... But they only seem to have it now for £15.99 (site was offering free postage at the time mind you).
Single track bikes have it for about £20
https://www.singletrackbikes.co.uk/m7b225s397p38589/Shimano_Alivio_BR-M4050_Alivio_Calliper/RS_GB
Evans about 22 squid. Still good value.
I am running one on my cx and one on the commuter (done 500 miles ish through swinley pretty much daily with no issues). Really don't notice any difference over the more expensive slx / xt calipers.
They back bleed really easily.
Think I've got a couple of new 486 calipers with pads in the spares box.
I did manage to look at the brakes at the weekend, just forgot to post. The caliper looked dry and clean when I took the brake pads off. So I walked the bike up a big hill and sharply braked all the way down the hill. The front felt back to normal and the rear while it felt better was a bit inconsistent. So the next day I did the same and the rear squealed again at the start but came good as I went down and now feels fine. So I guess even though the pads were new, after sitting around for months gathering dust they needed a proper bed in again.
timmy - thats not how bedding in works. what you re doing is burning of slight surface contamination.
Bedding in is 3 things. curing the pads with heat and pressure, conforming the pad to the disc and smearing a thin layer of pad material on the disc. NOne of these things will magically disappear over time when not used
Over the years, I think I have replaced calipers on about 90% of every shimano brakeset I have owned. Unfortunately it's a given, but that is offset against their lower initial cost compared to Hopes or Maguras. Also over the lifetime of a brake, including the cost of all the pads you will use, a bit more for another caliper isn't the end of the world. But it is another bit of faff.
And for a reason I don't know, they are more likely to fail if they have been sitting around for a bit. OP - sounds like you just need a new caliper.
Edit - looking at the caliper won't help much. It's only a very fine spray if it's leaking. A tell-tail (on a dry day) will be if it looks unusually dusty as the dust is attracted to the oil spray.