Bike Chain Problem

[email hidden] (Scott) wrote in :"]news:[email hidden]:

Quoted message said:

I have a novice question for you on bike repair. I've got a Trek 4300 mountain bike that I've only
had for a few weeks, and the chain managed to fall off the front sprocket. Being completely
ignorant about bikes, I put the chain back on to the small sprocket. It will now work properly if
the left shifter is on one, but not if it is on two or three.

Most bike shops give you a free tune up after a month. During that time, cables will stretch, so you
need the tune up to keep it shifting (and braking) smoothly.

I had the same problem with my new bike last year. I think it's an indexing problem, i.e. the number
on the gear-shift no longer corresponds correctly with the setting of the chains. You have Monday's
in Tuesday's, so to speak.

I took my bike back to the shop and they fixed it in a trice. By the way, I'm not sure the bike
wasn't badly indexed when I bought it. As I discovered in another thread, spanking new for a bike
does not necessarily mean ready to roll. A bike with a badly set derailleur will be more subject to
the chain popping off at odd and dangerous moments, as you described. When you put it back on, you
get it round the smallest sprocket because that's easiest, but if it was set in third gear and
you're manually intervening to force it into first, your indexing will be wonky.

Elisa Roselli Paris, France

Scott said:

It will now work properly if the left shifter is on one, but not if it is on two or three. Any
suggestions?