Bicycle Mechanics - How much play is normal in Cantilevers?
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02-09-09, 07:17 PM
I would hope none would be normal, but of course it's not a perfect world. I just acquired a 1990esque Trek 990 that looks great. The paint looks wet, and most of the components are in great shape. The canti's seem to have so much play in the pivots that the pads move about 1/16"+/- from front to back. I'm thinking I should just find a new set and get it over with. Those Avids on sale right now would look sweet and probably perform way better anyway.
98% of this bike is in stellar shape, so a brake swap wouldn't be too much of a hassle. I also have a set of Manitou forks with Deore XT brakes in very good shape. The fork has new elastomers. The DS2 fork on the bike is good however, so I'd rather keep it for now. It would involve switching to a threadless headset, a new stem, etc...
Should I ask this on the MTB forum? Me thinks they would ignore me because my bike would seem ancient to them, lol.,,,,BD
That is a lot of play. I have never used one with that much play, but I think it might make for a pretty noticeable shudder under heavy braking force.
It could be the post itself if worn down? I doubt it though. If so (and unless they are replaceable posts) you might be stuck. More likely the brass bushing that rides on the post is worn, and so new canti's would solve it.
Have you tried tearing them down and making sure everything is tight? Sometimes cleaning out all the grit and greasing the post threads will allow you to cinch them down a smidge tighter.
A 990 was a nice bike, I hope a solution presents itself.
02-09-09, 08:13 PM
Probably not the posts, at least I hope it isn't. Looking at the bike you'd never believe it spent more than a week or two in actual use. I will have to check my stash which has really grown in the last few months. I'm not certain that I don't have a set to match the brakes on the Manitou. I do know for sure that I have an NOS Deore XT FD:D.,,,,BD
02-10-09, 12:34 AM
I just love the cantis... In fact I prefer them to V's. Sadly in this part of the world one cannot but new catibrakesets anymore ( I am from Malaysia). everyone seems to be going for discbrake on new bikes. I am still assembling bikes using old Shimano 7-speed freehubs and have to resort to old cantis I salvage from junks...
That is a lot of play. ..I think it might make for a pretty noticeable shudder under heavy braking force.
Don't know about shudder, but I had a bike with near-terminal brake squeal that didn't go away until I did something cruel & unusual to cure the brake play.
It could be the post itself if worn down?
I've never seen a canti that pivoted against the post itself. Of all the ones I've pulled apart, or seen pulled apart there's always been a bushing (or two) in the brake arm. The bushing gets clamped firmly to the post, and then the brake arm pivots against the unmoving bushing.
There might be another bushing or sleeve thingy pressed in the brake arm as well to act as a bearing surface between the bushing clamped to the post and the brake arm.
More likely the brass bushing that rides on the post is worn, and so new canti's would solve it.
My bet is that these brakes have always been sloppy, even from assembly. Considering the surface areas, type of movement and forces involved, 1/16 is a huge amount of material to wear down.
02-10-09, 04:54 AM
Most of the bushing wear I've seen on cantilevers is in the bushing. Not so much wear all the way around, but a little from each side of the bushing. 1/32" or so from the front and back makes for some big slop once it's all said and done. It does shudder a bit under heavy braking. How could the brake arms be that loose since new? It seems hard to believe anyone would have accepted that amount of
slop in a new bike, especially one that costs as much as this one did..,,,,BD
..1/32" or so from the front and back makes for some big slop once it's all said and done...,,,,
But there's really no mechanical incentive for there to be any wear from the back,(unless there's some really weird fretting going on) so all that slop should come from the front.
..It seems hard to believe anyone would have accepted that amount of
slop in a new bike, especially one that costs as much as this one did..,,,,
Well, I've seen people quite happily ride on MTBs with the forks reversed, sus forks hopelessly seized and whatnot. I wouldn't hold it as impossible. You said yourself that the bike 's overall condition was very good - what simpler explanation to that is there than that the bike hasn't gotten ridden much?
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