Bicycle Mechanics - infuriating shifting problem
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Hi everyone - I have a 2003 Enduro Pro with the XTR shifter/brake lever combo. Recently this bike has begun randomly throwing the chain off of the middle chainring to the inner, or occasionally all the way off to the inside. I completely adjusted the front derailleur, cleaned and lubed, etc., to no avail. The teeth on the chainrings are straight and not badly worn, and my LBS checked the chain itself about 3 weeks ago and said it was fine. I have also checked the frame for cracks, but havent found any. This does not happen too often when the bike is in the stand, when I ride on pavement, or when I am climbing on a trail. It happens mostly in relatively smooth, flat areas, and in bumpy small terrain, like roots or baby head rocks. It does not happen when I go over something large. It does not happen much on descents, though living in Indiana maybe that is because there aren't many descents to begin with.
When this occurs I can usually get it back into the middle ring where it will ride for as little as 10 seconds or as much as 10 minutes before repeating itself. What could it be? This is killing me at races and is becoming more and more frequent!
Thanks for any help!
05-28-06, 04:50 PM
Check the teeth very closely for nicks, burrs or chips on both the inboard and outboard surfaces. It's not the front derailleur's job to keep the chain on a chainring, just to deliver it there.
Also check the chainline.
05-28-06, 06:43 PM
a friend had a similar problem...he had recently replaced his chain, a shimano 10 speed. note that he had not told me this as we stopped to adjust his front derailuer a couple of times and once his rear but it was still happening. our lbs...one of the best anywhere, took a look and said the chain was not put on correctly. shimano chains install with a special pin, everytime I've installed the thing, I always check the alignment of the pin with the other pins. I wasn't sure if the mechanic said if the pin was miss aligned or if the pin was put in from the wrong direction.
I personally perfer the chains with the quick link or power link.
That is a great starting point - I feel more hopeful already!:)
05-29-06, 03:26 PM
I had a similar problem while riding a friends bike a few years back. He told me later that the chain had some "frozen" links and had to be replaced to solve the probelm.
05-29-06, 11:58 PM
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Interesting post about the chain pin - I have never heard of that! I found a burr or two on the chainring and tried to file it down, and made sure no links were frozen on the chain itself - that's about all I can do before Saturday's race. Thanks for all the good info.
05-31-06, 02:32 PM
With a correctly adjusted low and high stop. The chain should start rubbing against the derailleur cage before slipping off on the inside of the small ring or to the outside of the big ring.
05-31-06, 04:37 PM
This doesn't address the problem of losing teh chain in the first place, but I'd recommend putting a chain watcher in place. Basically a plastic thingy that clamps below the front derailleur and snuggles up close to your small ring. I had to do a bit of filing to get one to fit on my 04 Enduro, but now that it's on I get NO dropped chains. (used to happen on really rough descents sometimes). This won't solve the problem of your chain dropping from your middle ring, but at least you won't lose it completely.
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