TheJ Posted August 17, 2016 Posted August 17, 2016 Got bike back yesterday after a quick checkup from the bikeshop. Then, rode a night race last night and noticed the back brakes (XT) aren't releasing lekker. You had to use the brakes like a scissor... use the brakes and when done, push them away from the bars again otherwise the rotor drags. Every time. Took bike back to the bike shop this morning. They let me know now they bled the brakes again but that the brakes weren't compatible with the rotors. WTF? I would have thought a 160mm steel rotor... is a 160mm steel rotor? I get the different between a 6 bolt and center lock rotors but really? The calipers mount and have adjustment built into the bolt holes, so what does the rotor matter? All the reading I've done online says its no problems.
Riaan373 Posted August 17, 2016 Posted August 17, 2016 Previous 785 xt levers are known to get sticky....
Captain Fastbastard Mayhem Posted August 17, 2016 Posted August 17, 2016 Got bike back yesterday after a quick checkup from the bikeshop. Then, rode a night race last night and noticed the back brakes (XT) aren't releasing lekker. You had to use the brakes like a scissor... use the brakes and when done, push them away from the bars again otherwise the rotor drags. Every time. Took bike back to the bike shop this morning. They let me know now they bled the brakes again but that the brakes weren't compatible with the rotors. WTF? I would have thought a 160mm steel rotor... is a 160mm steel rotor? I get the different between a 6 bolt and center lock rotors but really? The calipers mount and have adjustment built into the bolt holes, so what does the rotor matter? All the reading I've done online says its no problems.some avid rotors, from what I remember, are marginally thicker than the shimano counterparts. Ignore me. I are stupid.
Surprize Posted August 17, 2016 Posted August 17, 2016 Previous 785 xt levers are known to get sticky....I also found that out this week... Took my bike to the lbs because of a sticky rear brake and was told that the brake lever was completely seized up. Also XT 785 which is a little more than a year old.
Meezo Posted August 17, 2016 Posted August 17, 2016 Got bike back yesterday after a quick checkup from the bikeshop. Then, rode a night race last night and noticed the back brakes (XT) aren't releasing lekker. You had to use the brakes like a scissor... use the brakes and when done, push them away from the bars again otherwise the rotor drags. Every time. Took bike back to the bike shop this morning. They let me know now they bled the brakes again but that the brakes weren't compatible with the rotors. WTF? I would have thought a 160mm steel rotor... is a 160mm steel rotor? I get the different between a 6 bolt and center lock rotors but really? The calipers mount and have adjustment built into the bolt holes, so what does the rotor matter? All the reading I've done online says its no problems. https://community.bikehub.co.za/topic/155987-fixworkaround-shimano-xt-m785-brake-lever/ this to fix the problem, they can bleed the brakes a billion times, it wont fix the issue... This works above, tested and running on close to 5-6 sets i know(worked) of
Captain Fastbastard Mayhem Posted August 17, 2016 Posted August 17, 2016 https://community.bikehub.co.za/topic/155987-fixworkaround-shimano-xt-m785-brake-lever/ this to fix the problem, they can bleed the brakes a billion times, it wont fix the issue... This works above, tested and running on close to 5-6 sets i know(worked) ofah yes, I remember this.
TheJ Posted August 17, 2016 Author Posted August 17, 2016 just run the OEM Shimano disks.... Never came with rotors.
TheJ Posted August 17, 2016 Author Posted August 17, 2016 Let me maar rather keep quiet until I have more information.
JXV Posted August 17, 2016 Posted August 17, 2016 There are two return springs in the system. One between the pads and one inside the piston at the lever. Both help to push the lever back and retract the pads. Some possibilities : - If there is air in the system the pads might drag but the lever would not because the air compressed under braking would expand on release and assist the lever return spring. I doubt it is an air issue. -If the LBS neglected to clean the exposed portion of the pistons before pushing them back to accept the new pads they may have dragged some gunk in between the cylinder bore and pistons in the caliper. This could cause friction and delay pad retraction. However normally when this happens only the one piston seizes and the other does all the moving. It would only cause slow retraction if both caliper pistons got stuck or contaminated. -If the master piston/seal in the lever has deteriorated it can also cause drag. Your levers only a year old so this should not happen. However if someone used DOT fluid in your mineral oil brakeset this could cause the seals to deteriorate and get sticky. Caliper seals can also be affected by DOT fluid. Even if they bled it with equipment that was previously esposed to DOT fluid it is enough to contaminate the mineral oil and will eventually deteriorate the rubber seals. - I very much doubt it has anything to do with the brake disc. -another possibility is that the return spring at the caliper could have been left out or got mangled on installation. This is the metal spring that is sandwiched between the pads when you insert them. Make sure no bits of the old spring were left behind in the caliper and the new one is correctly installed. Sent from my SM-G900F using Tapatalk
Meezo Posted August 18, 2016 Posted August 18, 2016 Let me maar rather keep quiet until I have more information.Ny just wait for tomorrow
Skinnyone Posted August 18, 2016 Posted August 18, 2016 I have run Avid rotors on Shimano systems and vice a versa many a time (as well as Formula/Magura/Hope combo's) the piston in the caliper (any system) is self adjusting to the disc/pad thickness - otherwise one would have to keep adjusting the system to accommodate wear on the pads and discs. I have found that the 785 series of Shimano levers have had similar issues as the 2011/12 Avids where the lever internals became sticky and hence prevented the fluid from returning to the master cylinder/lever and letting the pistons retract properly. I have a feeling this is the case...If you purchased the brakes new then perhaps try putting in a warranty claim, if you purchased used brakes then get your LBS to try new levers to see if that makes any difference. JXV has a point about the return spring between the pads, however, this spring only pushes the pads apart and keeps them against the face of the piston away from the disc, they have very little effect on the retraction of the pistons in the caliper.
Halfdoesyn Posted August 18, 2016 Posted August 18, 2016 I have run Avid rotors on Shimano systems and vice a versa many a time (as well as Formula/Magura/Hope combo's) the piston in the caliper (any system) is self adjusting to the disc/pad thickness - otherwise one would have to keep adjusting the system to accommodate wear on the pads and discs. I have found that the 785 series of Shimano levers have had similar issues as the 2011/12 Avids where the lever internals became sticky and hence prevented the fluid from returning to the master cylinder/lever and letting the pistons retract properly. I have a feeling this is the case...If you purchased the brakes new then perhaps try putting in a warranty claim, if you purchased used brakes then get your LBS to try new levers to see if that makes any difference. JXV has a point about the return spring between the pads, however, this spring only pushes the pads apart and keeps them against the face of the piston away from the disc, they have very little effect on the retraction of the pistons in the caliper.Doubt very much that it's the rotor. If it runs freely it'll work. As others have said, look at your lever mechanism.
droo Posted August 19, 2016 Posted August 19, 2016 Lever not returning because of rotors eh? Did he need toilet paper to clean his mouth after he said that? 3 options here: 1. Wrong fluid used2. Lever seal is sticking3. Piston seal is sticking As mentioned earlier, the lever is the most likely culprit. JXV, the spring between the pads doesn't help the pads return, it's not nearly strong enough. All it does is keep the pads against the pistons. Maguras attach to the pistons with a magnet and have no centre spring, and on some Hayes designs the pads attach to the piston, and again no spring.
Bobbo_SA Posted August 19, 2016 Posted August 19, 2016 I have a new in box right hand side M-785 (Black lever with Silver res cover) lever, PM me if you're interested.
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