Do chain guides such as the one pictured really work? I am building up a carbon fiber frame and I know how much damage a dropped chain can do to a CF frame. I can either try a chain guide or wrap lower parts of the frame in grip tape, or both.
'''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
I use them on all my bikes because I have triple cranks on everything. A number of Pro teams use them on their racing bikes even with double cranks and that's a pretty good endorsement. They are cheap insurance and, yes, they do work if you adjust them properly.
I'd particularly use them on carbon frames. A dropped chain will probably only scratch up a steel or Ti frame but it could destroy a carbon one. A "properly adjusted" front derailleur shouldn't drop the chain but........
I use one on both of my (aluminium) roadies. It does help, cause if the chain throws off inside on a quick drop from large to small ring, it will (in most cases) "pick" the chain up and drop it onto the small ring again. Like I say, most cases. I have had a few occasions where I've had the combination of changing down + power + a bump which causes the chain to not put itself on again. Few and far between though. They're more for the odd drop instead of full power change down.
And more than worth it for a frame you dont want to scratch.