I seem to be having a run of nasty mink on my disc brakes and I think it might be due to some leakage round the pistons on my XT disc brakes.
I had the same problem last year on one brake and replaced the caliper, which seemed to sort it but I don't want to have to be buy new calipers again.
If everyone reckons they do leak, any recommendations for alternatives (are XTRs better)?
Shouldn't be leaking - unless you've damaged the seals? I have XTs that are 4 years old and they're still perfect.
My recommendation is avoiding stuff with mineral oil 
Get hope or formula. I can't see any other brakes on the market getting close in terms of quality.
I got some new XT brakes about four years ago; this year I have replaced both calipers due to leaking seals. I think they were killed by living in a shed the last few very cold winters. I don't know if other brakes would have been better, but while the brakes are excellent I don't think the caliper seals are (or were) particularly hardy...
I had some SLXs that lasted only 7 months. I got them refunded under warranty and replaced them with elixirs. More because now all my brakes match so I have less pads to buy.
People think they are unreliable and hard to service but I've found them to be good. New seals can be bought so they are much cheaper to service.
I think I'd go with hopes if I had the money because of ability to fully service them.
had 775's on mine for 2 years & no issues
I've had a Deore caliper leak on me and had to replace it and a fella I know had similar...........so it does happen.
Juan
In theory mineral oil is better because it lubricates better...I think I also heard that it absorbs water less.
They leak no more than any other brake for a given number of units.
All mass produced products will have some problems on a percentage of the run.
it's the customer service when things do go wrong that makes the difference for me.
Hope and Shimano offer the best aftermarket service IME.
The dry boiling point of DOT fluids is higher, but the wet boiling point of mineral fluid is closer to the dry boiling point. So you see fewer complaints of brake fade on mineral systems.
A thought just occurred to me aswell. Some mineral systems are not so tolerant of high performance fluids such as LHM. If your brake has been bled with LHM in the past, it could have hardened the seals and causedthe leaks.
Just a thought, but may have some relevance.
I've had 3 callipers leak (all XT) as they have no serviceable parts you have to buy new callipers. They seem to go on the seals and leak both on the inside and outside (on the silver Boar/Piston housing)
JuanIn theory mineral oil is better because it lubricates better...I think I also heard that it absorbs water less.
To be honest, the only persons who use shimano brakes around here are the ones whos bike was fitted with them. Formula is the favourite choice. Then comes hope. Then avid and shimano are both hopeless. At the trans provence, no formula ever required a bleeding. I can't say the same about the avids...
Maybe true, but DOT fluid does not "disappear" magically like shimano brake fluid.
I have no idea what this means. 
It's those damn froggies. I think they use it for cooking and are always stealing it out of parked-up bikes.
It's means my GF brakes need regular top up of fluid. I have check them for leaks, but there is none, and the LBS have told me similar, fluid in shimano brakes just disappear. Where I don't know, but it disappear.
Oh and most of French cooking oil production is exported to the northen part of the UK apparently to fry chocolate bars...
I have check them for leaks, but there is none, and the LBS have told me similar, fluid in shimano brakes just disappear.
Not very, err, scientific, is it?
juan - MemberJuan - your LBS is talking bolloks. For instance, I have one set of Deores that have never been bled in 5 years and still work perfectly. I'd find someone that knew a bit more what they were talking about.
It's means my GF brakes need regular top up of fluid. I have check them for leaks, but there is none, and the LBS have told me similar, fluid in shimano brakes just disappear. Where I don't know, but it disappear.
Not very, err, scientific, is it?
Druidh - they will have small leaks past the seals - thats where the fluid goes- as many folk are now finding there seems to be a real issue with this with shimano brakes
The xt's on my s-works suffer from phantom disappearing fluid. No evidence if where it's gone, must be past the seals. Otherwise it's all good.
Yes. Mine (m760 XT) were fine until last winter, rode around a fair bit in the snow etc and noticed they felt wooden, no retardation and the noise was like a banshee.
Would seem cold weather did it for them. Crazy. As already mentioned you cant get new seals to service them either.
Out of 7 shimano calipers ive had, 4 were new. The only one that leaked was a second hand xt one. I've never experienced fluid disappearance, but this could be down to the fluid in use. I've used lhm since day one.
Ive experienced the wierd "feel" in cold weather, but they were fine once it warmed up again.
I rate shimanos very highly from my original Deore M555s to my current M775s. Wouldn't have avids or Hayes though. If shimano made spare seals available they'd never sell any new brakes!
I've been maintaining a fleet of over 20 'Haro flightline expert' mtb's over the last two years.
They are all fitted with shimano deore hydraulic disc brakes.
At the beginning, at least half the brakesets were replaced under warranty for contaminated pads.
And slowy since then the others and some replacement brakes have all become leakers.
It is impossible to actually see them leak, but the munute amount of fluid that makes it past the 'piston seals' renders the pads useless.
Squeeeeeellllll on!
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