I was pretty impressed by this simple video which de-mythifies at least for me rear gear adjustments.Before watching this video I thought most adjustment was done on the front handle bar but truth is very overpowering at least for me.Watch it here
http://www.youtube.com/watch?v=SkzvfCaIbyQ&mode=related&search=
http://www.youtube.com/watch?v=SkzvfCaIbyQ&mode=related&search=
