2009/8/24 ternst <ternst1@cox.net>:
> Fairly obvious.
> Its a guide to keep the chain on a single chainwheel so when shifting on the
> rear derailleur the chain wouldn't pop off the top and derail.
> All of you have seen the wave in the chain in fotos taken in action on roads
> and this same action could unseat the chain on top when shifting.
> The chain angle on many bikes could also cause the chain to climb when in
> the out or inside cogs depending on shape of chainwheel tooth and chain
> interfacing.
> Crunch, crunch, "Oh S---!"!!
> Many of you have beenther even with a conventional double/triple chainring
> front derailleur cage.
> Ted Ernst
Indeed. I've always thought that having a rear derailleur without a front didn't seem like a great idea. If you are going to run a chain guide anyway (which you should) with a single ring, why not use two rings and an actual front clanger? Aside from the more useful range of ratios, you can take better care of your chainline too that way if you understand how. You'll even note some racers running TTs keeping the FD and double rings on dedicated TT bikes, although they have no intention of using the small ring, for that very reason.
Kurt Sperry
Bellingham, Washington
USA