7sp Cassette on 9sp drivetrain

[Cycle Fan]

Hi Guys,

 

I have an OLD rear wheel (MTB) that I want to use for the indoor trainer. The problem is, it has a 7sp cassette and my MTB is a 9sp. Will I damage the drivetrain by using it as is and only using the 7 gears?

 

Alternatively, will a 9sp cassette fit on the freebody that currently has a 7sp cassette?

 

Thanks for the help.

[Tiny K]

Yes you will damage the casette by matching the two.

 

(AFAIK) the 7 speed difference is a shorter hub. measure the shaft that the skewer goes through and compare to your 9spd wheel. If the same, then 9spd cassette will work.

[Cycle Fan]

Thanks, it's an old cassette so not too worried about damaging it - will I damage the derailleur or chain as well?

[David Marshall]

You won't damage the derailer or the chain. The derailer will do what the shifters tell it to. Your problem may come in with the difference of cable pull between the 9 speed and 7 speed shifters (the spaces between the gears on the 7 speed hub and the 9 speed are not the same). If they were the same - no problem as you would just have to set the derailer Hi/Lo limit screws. Furthermore I doubt if you can replace the 7 speed cluster(??) with a 9 speed casette. I don't think it will be worth the hassel anyway because every time you change wheels you will have to reset the limit screws and possibly have to adjust the gears.

[Cycle Fan]

OK thanks - so basically not advisable

 

Damn - thought I was onto something there...