Fitting an 8speed cassette to a 7 speed axle.

[Donut65]

Would it be possible to fit a 8speed cassette to a wheel that has a 7 speed cassette. The bike in question is a 92 raleigh peak, the 7 speed gear shifters are knackered but I have a new set of 8 speed shifters so was wondering if I could fit a new 8 speed cassette to the rear wheel/axle and use the new 8 speed shifters. Hoping it can be done as I can pick up a 8 speed cassette for a few quid but to buy a new set of 7 speed shifters could be quite pricey!.

 

[Rampage]

No, unless it has an 8 speed freehub.

 

[JoeG]

The cog spacing is the same for both 7 and 8 speed. 8 speed uses a wider freehub body to make this possible. You should be able to use the derailleur limit screws to prevent the rear derailleur from moving to where the 8th cog would be. It would be just like never using your biggest (8th) cog on an 8 speed cassette.

 

[cce]

The cog spacing is close enough for both 7 and 8 speed. 8 speed uses a wider freehub body to make this possible. You should be able to use the derailleur limit screws to prevent the rear derailleur from moving to where the 8th cog would be. It would be just like never using your biggest (8th) cog on an 8 speed cassette.

FTFY

 

[Donut65]

Thanks guys, makes sense.

 

[THE ARS]

You could dish the big cog.

You know, if you get really bored.

http://sheldonbrown.com/chainline-multi.html#spoke

 

[hamster]

No, you can't simply dish the largest cog - the stack of cogs and spacers will still be the same length! :facepalm:

You can fit an 8 speed freehub, but then you have to redish the wheel. It's simpler to buy the correct shifter. You might get away with running the 8 speed shifter on the 7 speed cassette but it's tetchy and needs new cable outers and everything kept clean. It's best to set up indexing from the 3rd smallest cog rather than the smallest, so that the error of 0.2mm per click averages out more.