Originally Posted by
cny-bikeman
There's no logical reason for the chain length to affect rubbing on the chainwheel, which is affected only by the angle between chain and chainwheel. The only functional reason a chain needs to be shorter is to keep the pulleys nder tension and in better position
If the chain was originally sized to allow a 53/34 big-big combination it could indeed go completely slack in a 34/11 or 34/12 combination.