If my worn XT brake pads …
This is rear, 160mm rotor, IS frame mount, post mount calliper.
With a little more thought – this is plainly not right. Because a) it’s hard to tell visually from above how much the pad is worn b) on my night ride last night the rear brake more or less ceased to function without notice (possibly because the top unworn parts of the pads finally made contact over the rotor, which was then running more or less freely between the lower worn parts of the pads), rather than the slower degradation and clunking that usually happens with worn out pads.
(Second hand bike).
Posted 4 years ago
Agreed, I put new pads in but I’ll get proper Shimano adapters, until then that bikes’s off the dirt. There’s a similar wear patten on the front (post to post, 180mm) so that’s probably a wrong adapter too.
My rear brake failed (well maybe there was 10% left) as I was JRA last night, rolling back home on the flat. Had this happened at other times of the ride the outcome may have been a little less pleasant.Posted 4 years agossboggySubscriber
My XT rear does that on my singlespeed but only leaves a arc of around 1mm and that’s with a 160mm shimano rotor and shimano adapter so I can only assume that the disc mount on the frame is very slightly out. Also used to have similar problem on some old Pace sus forks, I used to remove the pads when they were half worn and file the ridge off so the brakes continued working to the end of the pad lifePosted 4 years ago
@hainman there aren’t any spacers pushing the calliper further from the axle/frame than it could be, so that’s not it
it’s either (in order of most to least likely IMO):
* incompatible adapter for the rotor, or the calliper, or both
* compatible adapter mounted wrongly (backwards mostly)
* incompatible rotor, for the calliper
* frame issue
anyhow now I understand why my rear brake stopped working last night, I’m gonna buy a Shimano adapter and try that.
@greeble for surePosted 4 years ago
Update: I took off the installed rear adapter, it says on it “185 F ->” with the arrow and F presumably indicating the orientation. There are no other branding or marking on it at all.
I put on a Hope mount F (Post to IS 160mm) for the interim (a Shimano is en route), pad to rotor overlap is perfect as far as I can see.
Oddly the removed mount arms are only a few mm longer than the Hope mount arms, that matches up with the pad wear pattern too … but if the mount is intended for a 185mm rotor I’d expect to see a 12.5mm difference with the 160mm rotor mount.
Presumably the difference must be made up in calliper designs, and the fact this adapter almost works with XT callipers on a 160mm rotor explains why the previous owner thought it was an acceptable setup.Posted 4 years ago
Yeah the removed adapter is Avid, like this, http://www.chainreactioncycles.com/Models.aspx?ModelID=13721 “Post to Front IS 185mm”Posted 4 years ago
Don’t know to be honest, I suspect he put the bike together from bits but didn’t ride it much. At a cursory glance it looked like it was ‘OK’, it’s not until it comes to a pad change/(brake failure!) the issue becomes obvious.
The setup’s pretty dangerous actually, the rear went from 100% to 10% instantaneously, without any warning or feedback you’d usually get from wearing pads (because they weren’t worn out). So these things are worth checking on second hand bikes!
And from now on I’ll always match calliper and mount brands.Posted 4 years agosharkbaitMember
Just changed from old IS mount hopes to post mount Hayes on my bike and bought a used shimano mount for the rear. Fitted the rear calliper loosely and all good, did the final tighten and the calliper was touching the edge of the Hayes rotor and the pads were fractionally too far ‘into’ the rotor.. Used a pair of IS mount shims in between the adapter and the calliper and its now spot on.Posted 4 years ago
The shimano mount must have been out by less than 1mm butt it made all the difference.
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