buckstoy

Hello, I've been having a problem with my Jamis XLT3 mountain bike. The problem is my chain is falling off the front middle ring usually when I am climbing up something but not always. I have replaced the middle ring, the chain, the cassette, and the front and rear cables. Just riding around everything works fine and shifts great but every once in a while it falls off. I looked at it today when it happened and the chain was off the bottom of the ring and still across the top

powers2b

Are you trying to shift the front DR while climbing?
That is a big no-no.

Enjoy

buckstoy

No, I don't try to shift it while climbing, I'm staying in the same gear and trying to power up stuff and I'll here the chain start popping! It truly is maddening! Thanks for the reply!

diff_lock2

lol yeah dont even think about it lol, i hate that sound of a bad gear shift, OUCH.. also when you have probs with the DR's that sound just kills...

buckstoy

Yeah ouch is right! I think I would rather have brake problems than shifting problems.

KevinF

A friend of mine had this problem for a while; in her case, it turned out to be a mis-aligned frame. Sheldon has an article on how to check here: https://sheldonbrown.com/frame-spacing.html (scroll down a ways). Any shop should have the fancy tool that will diagnose mis-alignment issues as well.

He also has another interesting article on auto-shifting here that might be interesting.

buckstoy

I was starting to think along these lines, the frame is basically a four bar design so I was wondering if there was excessive slop in the pivots? It seems that this could cause the chain to fall of the front, but I tried grabbing the back tire in one hand and the seat tube in the other (with the fork clamped down) and didn't see much lateral movement. Thanks for the link to the articles though, I'm going to try the string method.

ebbett

Is it a uni-directional type of chain? 99% of chains aren't, but the new Dura-Ace chains, for example have a connecting link that needs to go on in a certain direction. If you reverse it then you'll have problems w/ the chain falling off.

buckstoy

I've never heard of such a thing! Does the DA chain have a directional arrow? I don't think mine is, it's a SRAM 9 spd chain I don't think there's anything like that going on with it, thanks for your help.

NoRacer

Is the chain the correct length? Too much length and you could have 'slippage', especially on the rings and cogs that get the most use.

Al f R

I think you have the bull by the horns! The chains strength is enhanced by placing the pin through the outer plate first, in the direction of travel. It has nothing to do with the chain falling off the rings as described by buckstoy.