Bicycle Mechanics - Can a 7 speed rear derailleur handle 8 cogs?

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cycletourist
02-13-04, 07:11 PM
I am building a new road bike with an 8 speed wheel and I want to cannibalize whatever I can from my old 3x7 hybrid. Can I use the rear derailleur or will it not handle an 8 speed cassette? Indexing won't be an issue because I am using bar end shifters in friction mode.

SteveE
02-13-04, 08:39 PM
Cycletourist,

Can you measure the distance between the smallest and largest cogs on the two cassettes? If the distance is the same between the two, I wouldn't think you'd have any problems as long as you're using friction shifters
Rev.Chuck
02-13-04, 08:50 PM
If you are friction shifting, you should have no problem

dafydd
02-13-04, 09:18 PM
I gave my housemate suntour retrofriction barcons and a cyclone mkII derailleur--which he shifts over a 9-speed cassette. comes a little close to the spokes but otherwise it works fine.
sch
02-13-04, 09:30 PM
I used a '70s era five speed rear der on an STI equipped 8spd without any trouble when I retroed a PX 10 with a cast off 8spd setup. (Fr der also worked
til it broke a screw out of a casting and was replaced.) Steve
madpogue
02-13-04, 09:47 PM
I would think that even with indexed shifting, you should be okay. The detents are always in the shifter, whether it's STI/RSX, grip, crapid-firer, thumb-top or whatever. Those detents correspond with the position of each cog. As was said, if the derailleur has sufficient range, and can handle the range of cog sizes, you should be good to go.