7speed to 8speed conversion

The Rookie

We're building a commuter bike for my daughter, predominantly using bits from a Giant, we have a good rear wheel with 7speed cassette, can it be converted to 8speed by using a 9speed cassette and dropping 8th or 9th gear? (yes I know that each gear is a little narrower on a 9speed cassette)

Obviously have to use a 9speed rear mech and shifter and accept we won't have the 'end' gear on the shifter.

Simon

gbsahne001

silly question but if you're putting a 9 speed cassette on it plus 9 speed shifter, why wont you be able to use all 9 gears?

The Rookie

I was under the impression that the 8-9 speed freewheel was wider than the 7 speed - iknow 8 and 9 are the same (5-8 speed having the same gear pitch, 9 speed having a smaller spacing between gears) thus a 9 speed cassette won't fit unless it's narrowed, hence my suggestion to leave out one of the gears (so it wouldn't be 9 speed anymore would it!)

Simon

gbsahne001

ok, with you now; you'll assemble the 9 speed block onto the 7 speed freewheel until you can't get any more of the end gears on it.

Seems an expensive way just to get one more gear.

nicklouse

yes to what you plan but also you could go 9 if it is a hub and body and suitable frame. Also check that the body really is 7spd as often 8/9s are used with a 4,5mm spacer and a 7spd cassette.

have read http://sheldonbrown.com/k7.html



a freewheel will not do what you want see http://www.sheldonbrown.com/free-k7.html

The Rookie

OK, thans Nick, I was pretty sure you would know the answer, first thing I'll check for is a spacer, as the wheel is off a circa 2004/5 it is possible it has an 8sp width mounting I guess, frame is a 135mm wide 09 Claud Butler so pretty sure that would be fine.

Simon