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I've got M785 XT brakes on my bike, had them for around a year. All that time they have never seemed right, in that they deteriorate very quickly. I've bled them at least 5 times and I'm very thorough with it, using every trick that's been on any STW thread, the epic method, the Shimano instructions - everything. After bleeding with the bleed block in they are rock solid. After putting the pads and wheels back in, but before riding anywhere, they are rock solid. Then I ride it and after not long at all they are spongy as **** again, and remain that way. I've tried at least half a dozen different pads, sintered, organic and mixed, and it makes no difference.
What's going on with them? Can they leak in use and do this? I cant think what else it could be?
Sounds like a leak somewhere. Have you had a look at the hoses + connectors for fluid?
Yes, and it is present under those rubber covers. I have previously assumed this was just leftover after bleeding because I couldn't see it pumping out when I pulled the levers, but perhaps in hindsight that was an incorrect assumption?
Do the brakes make a horrible juddering squawk just as the bike rolls to a stop? That's a sure sign of oil or brake fluid contamination.
I've not noticed that ever. You mean pad contamination?
Yes, it only takes a small amount of brake fluid to get onto the pads and it spreads out and destroys the friction. Take the pads out and stick them in the dishwasher and clean the discs with alcohol or glass cleaner.
I've cleaned the discs everytime I change pads, never bleed them with the pads in, and clean the calipers very thoroughly with IPA before putting the pads back in. If its that then I've managed to do it to at least 10 pairs of pads (5 varieties front and rear), which I doubt.
I bought these brakes recently. Not been as impressed with them as the reviews led me to believe i would be. Too much lever throw for my liking. The little screws to adjust this seem to be next to useless. I'm sure they can be improved with a bit more tinkering; I'll give it a whirl when I'm free.
Yes, and it is present under those rubber covers
could be that the that the nut has been over tightened and crushed the olive to the point where you are no longer getting a good seal? not that likely, but if you are finding oil under the cable sleeve, and for the sake of a couple of quid, it would be worth replacing the barb and olive and see if that makes a difference.
also check the seal at the calipre end
Ok thanks.
If it was leaking at the caliper, i'd have thought it would have contaminated the pads by now and they'd be squealing. Are you getting a spongy lever on both brakes?
I bought some Deores that did this, they had weeping olives at the calliper end on each one, new olives and a bleed sorted em out..
You have to be careful when fitting the hose with the olive into the caliper that the olive doesn't fall off the end of the hose and go into the caliper wonky because it won't properly seal and weeps over time and contaminates the caliper and pads..
I bought these brakes recently. Not been as impressed with them as the reviews led me to believe i would be. Too much lever throw for my liking. The little screws to adjust this seem to be next to useless. I'm sure they can be improved with a bit more tinkering; I'll give it a whirl when I'm free.
Remove wheel; pump lever once, maybe twice; re-insert wheel. Lever throw = significantly reduced.
Also see Hope video on centralising calipers & balancing pistons, which is fairly straightforward with the use of a small flat-head screwdriver if you're not using finned pads.
What's going on with them? Can they leak in use and do this? I cant think what else it could be?
I had similar problems when I changed to Goodridge hoses. Re-cut the hoses & re-installed steel fittings & the problem went away, so air must've been getting drawn in somewhere. Did you shorten the hoses when you got them? Sure the olive & insert aren't mangled?
Are you getting a spongy lever on both brakes?
Yes, both brakes.
I've never had the hoses put of either the caliper or lever since I got the bike (new). Seems a logical possibility though.
defintitly worth doing if you've been bleeding correctly, there shouldn't be any fluid under the rubber cap and this could be the sign the olives and inserts were never installed correctly, and thus leaking and drawing in air. As the bike was new with those brakes, someone may have shortened the hoses in a cack-handed way before you bought it..?
Maybe. I'll see what they say and then maybe have a look at that. Good job I have a litre of brake fluid!
I'd guess the seals in the levers will have died. 2 year warranty on Shimano brakes and I've just had a set of 1 year old xt's replaced with new under warrnaty for it.
got xta 15 months old solid pull on leaver after bleed, first since I bought them. I think you have a leak/seals problem. You used right oil - not flaming but ...
I've emailed the company to see what they say, I guess they'll know if it is a regular occurrence
No, fair question? Pink Shimano mineral oil is all they've ever seen.
Then I'd agree with the OP and get the hoses and olives refitted. There a cracking brake
That's what I read, repeatedly, yet have never found them so, so there must be something not quite right.