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I'm having a strange problem with my rear brake, when riding along at reasonable speed, if I pull the lever it will just come all the way back to the bar with seemingly little resistance. It's braking hard enough to lock up the back wheel at this point, but the lever is getting pretty close to the bar at this point. It just feels like the resistance doesn't ramp up properly.
When the bike is stationary though it bites just as sharply as the front brake. I've bled it, put new pads and rotor in, and burned it all in, and the free stroke is screwed into the lever as far as it will go. It only seems to do this on occasion, sometimes it feels fine. Really stumped here, I'm hoping someone has some good ideas.
Apologies to the STW zealots for resurrecting this thread, but I am having the exact same trouble as the OP.
Same story; Bought brakes, trimmed hoses, bled, new pads etc etc but still on fast descents I have the same soft lever feel.
I get no bubbles when bleeding the brakes so I doubt its air in the lines, also I've bled the things umpteen times now with all the official shimano gubbins so unless I'm a completely hamfisted gorilla I don't think I'm doing anything wrong. I've also stored the bike upside down in an attempt to see if there are bubbles in the caliper, but braking is just the same the next day.
The brakes work FINE on slower stuff...I just dont geddit!!!
Answers on a postcard please.
Many thanks, and OP if you found a solution please let me know.
Hi,
I had the same problem with my rear brake!
New pads, fully bled but no power. I was at the point of getting a new caliper when I noticed every time I pulled the lever there was a slight bulge in the hose next to where it enters the caliper connector! The connector was badly crimped onto hose, after a bit of web searching I found this is a fairly common problem with these brakes, some had it sorted under warranty, I had a spare braided hose so fitted that and it is now better than ever!
Hope this works for you! It was driving me nuts
Regards
Steve
Unfortunately I can't even help, it just fixed itself after I moved the lever a bit further away from the bar, and it's all been fine, even surviving a week in the alps with no problems at all.
I had saints and they were finicky to say the least, was fancying xtr but worried they will be the same
From Raisinhat's description and cure, it sounds like the master-cylinder piston may be masking the fluid return port back to the reservoir sometimes(piston not returning fully). It shouldn't be possible for this to happen unless something's taken a knock/been distorted/dirt or similar taking up clearance/free stroke screw forced past it's limit.
What pads are you using? The proper Shimano ones are a lot better than some ashima ones I fitted. Apparently the Ice Tech rotors don't like sintered pads?!? or is this just maliscious rumour?
We've had quite a few problems with these brakes in the shop, there is a defect regarding the fit of the seals in the master cylinder that causes loss of fluid pressure - this can happen out of the blue for no reason whatsoever and it can disappear for no reason whatsoever. Every brake we've sent back has been found to have this problem and whilst it doesn't seem to affect every M785 brake it has affected a number of them so the problem must lie in a manufacturing defect or incorrect assembly/pinching of the seals in the master cylinder piston assembly.