Chainset loose or bent?

Doc Daneeka

Hey folks,

Bought a new bike recently and have a query in relation to tuning the gears as there is a little rubbing on the front derailleur in the highest gear. Haven't really gone doing so myself yet as LBS said to bring bike back for a tune up after a few weeks.

One thing I am unsure of is when I look down on the chain when cycling it shifts slightly from side to side over the course of a pedal turn when judged against the derailleur. Now my question is does this indicate a potential problem or is it simply due to the sprockets shifting the chain for even wear.... assuming they do this! I would guess there is maybe a couple of mm in it from side to side.

Doc

A small amount of movement of the chain/chainring relative to the front mech on each pedal stroke is normal and is due to the frame flexing slightly on each pedal stroke. If it is excessive it could be due to a bent chainring or a loose bottom bracket. Grab each crank and try to move them perpendicular to the bike, to check for play in the bottom bracket, although that's unlikely if the bike is fairly new. To see if it's a bent chainring spin the cranks with the bike in a workstand (or upside down) and look for lateral movement of the chainring relative to the FD. If there's no chain rub on the FD I wouldn't worry too much.

IM0

Doc Daneeka wrote: »

LBS said to bring bike back for a tune up after a few weeks.

Doc

this^