Bicycle Mechanics - Grip shifter to Rapid Shifter Question

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PDA
Not the Slowest
05-22-09, 11:07 AM
I have a grip shifter 7 speed and was looking to perhaps upgrade to a rapid shifter.

Can I use a 8 speed Rapid shifter even if I have the 7 speed cassette.
Hmm maybe I can put a 8 speed on the back, not sure about the wheel.
If I don't change the back cassette will it still work?

Thanks

Rob

hernick
05-22-09, 12:24 PM
I don't think it would work - you can't put a 8-speed cassette on a hub meant for a 7-speed cassette. Some conversions are easy - like 6-speed freewheel to 7-speed freewheel. Or 8-speed cassette to 9- or 10-speed cassette. But 7-speed cassette to 8-speed cassette typically requires a rear wheel replacement, which is not worth it.

If you don't like your shifters, just replace them and stay with a 7-speed drivetrain. You can still find 7-speed shifters, like the MC40 (http://www.jensonusa.com/store/product/SL407A04-Shimano+Stxalivio+Mc40+7+Speed.aspx) if you want to keep your existing brake levers and the ST-EF50 (http://www.jensonusa.com/store/product/SL308B13-Shimano+St-Ef50+Shiftbrake+Lever+Set.aspx) if you want an integrated unit. If you get the ST-EF50, they are made in two versions, one for v-brakes and the other for cantilever and caliper brakes.

Plenty of new bikes are still sold with 7-speed cassettes, it's a perfectly sound and reliable technology. There's little point in upgrading to 8-speed.
Mr. Underbridge
05-22-09, 02:24 PM
It's doable. You can use what's called the "alternate cable routing", in which the cable is routed differently around the pinch bolt at the rear derailer. That technique is specifically to do what you want to do.

http://www.sheldonbrown.com/derailer-adjustment.html#alternate

However, hernick is correct in that 7-speed replacement shifters are available, and that's probably a better solution than adapting an 8-speed for the job. Around $25/set from, say, JensonUSA (including the models mentioned)

http://www.jensonusa.com/store/sub/146-Shifters.aspx?s=2101

AndrewP
05-22-09, 03:11 PM
It would be worth your time and money to put on and 8 sp shifter and doing the Sheldon B method, if you are considering a new rear wheel in the next year or so.