Having a real headache with the old Shimano Deore disc brakes on my singlespeed. I've always serviced them myself and they've been completely reliable for years but started playing up over the last couple of weeks - eventually fading completely on my ride home from work last Thursday on a long and steep road descent (V scary).
Since then I've flushed through with new mineral oil and bled them, thoroughly cleaned the rotors and swapped out the pads but they're still not behaving. They howl like a banshee - particularly when wet - and either don't engage or judder horribly.
My first thought was the seals had gone but there is no seepage that I can see and no signs of the pads being contaminated. The pads aren't glazed and I've done all the normal stuff to get them to bed in.
I fear they've just reached the end of life but the budget can't stretch to a replacement set so looking for top tips to sort them out.
Any ideas?
Cheers
you can pick up a new Deore caliper for around £30 or about £40 odd for a whole caliper/lever set.
they're not that expensive
http://www.on-one.co.uk/i/q/BCSOEDEM615/shimano_deore_br_m615_disc_brake_set_without_rotor
Am aware of it but unfortunately budget means zero bike expenditure at the moment. If I can't get them sorted I'll be rummaging through the parts bin for some V brakes.
I had a set of XTs which suddenly went a bit crap for no good reason. Bleed was good, lever feel was fine, pads replaced and rotors cleaned ~ but still a distinct lack of bite and power. The only thing that really made a difference was replacing the rotors ~ this might well help with your Deores as the supplied rotors are a bit cheesy. I've never found any concrete scientific proof, but I suspect rotors "go off" after a period of use.
Try lightly sanding the rotors with some fine sandpaper, give them a good clean after with IPA and see if that helps.
I had an older XT (M765) caliper that just didnt seem to have any power. One of the seals was letting the tiniest bit of air in, so they felt ok, but no power. This was after I replaced EVERYTHING else (lever & hose), so I knew it was the caliper.
There's no need to bleed them.
Pop the wheel out and pump the lever, maybe a few times maybe more until the pistons sit proud of where they once more. They pads may rub at first but only for a short while.
It does some stuff and makes them mint again, i have to do it a once or twice a week atm
Cheers guys. Someone also mentioned cleaning the pistons to stop them from sticking - what's the best thing to use for this, IPA again?
I have some old Shimano brakes that are about to get swapped for Hope (486 maybe? Not sure)
Rather than bin them you're welcome to them for postage (unlikely to be in Dartmoor soon).
The payoff is that you have to be nice to someone else sometime.
SprocketJockey - Member
Cheers guys. Someone also mentioned cleaning the pistons to stop them from sticking - what's the best thing to use for this, IPA again?
While it probably won't do any harm, I wouldn't be putting IPA near any of the seals. It might react with the seals.
I used to do material compatibility testing for a digital inkjet manufacter and one of the hardest things to find was seals & o-rings compatible with the myriad of chemicals that the chemists used to put into the ink. IPA was generally OK (and was mainly used as a cleaning solvent), but does react with some rubbers.
To 'clean' the pistons/seals the best thing to do is use a cotton bud (or similar) soaked in the brake fluid. Pump the levers with the pads out to get the pistons to extend (don't do this too far or they can pop out completely), clean around the piston with the brake fluid soaked cotton bud and push the pistons back in. Repeat a few times.
I've not cleaned the pistons yet. I'd do so with whatever's in the system.
If you want to clean the pistons and seals, soak the area around them with mineral brake fluid and work the pistons in and out.
Just dont let the piston come out more than 3mm or so, or you risk popping the piston out.
You should notice that the fluid around the pistons starts to turn a dirty grey colour.
Wipe clean and repeat the process a few times or until the fluid doesnt change colour much.
I tend to work on one piston at a time, holding the other one in place.
Obviously you need to do this with the pads and the wheel out and make sure you wipe the caliper clean of any fluid afterwards!
igm - that's fantastically generous. You're a gent. Will drop you an email with my details.
I was wondering why people were cleaning pistons with India Pale Ale.
Low alcohol content usually.