casette question

[weely]

Can I replace the 7 speed casette from my old bike and replace it with a 8 speed?

This would give me the option to use my old wheels on my new bike with different tires

 

[HLaB]

It not as simple as that unfortunately, at the very least you'll need to buy a 8sp derailleur and a 8 sp shifter.

 

[weely]

No... My new bike is 8 speed and my old one is 7 speed. I would like to use my old wheels on my new bike.

 

[HLaB]

I think there's a spacer on the 7 speed to make it the same spacing as a 8spd, you just remove that. I've never done it before somebody more experience will confirm or not.

 

[mickle]

When we moved from 7spd to 8spd the width of the free-hub body was increased to accommodate the extra width of the 8th sprocket and its spacer. You might be able to fit an 8spd free-hub body (and correspondingly longer axle) to your old 7spd wheel to allow the fitting of an 8spd cassette. I wouldn't bother, by the time you've tracked down an eight speed body which is compatible with your 7spd hub (if it exists), fitted an axle and extra spacers you might as well have bought a new 8spd wheel.

However, seven and eight use the same spacing so everything is semi compatible inasmuch as the clicks on the shifter correspond to the sprockets, the mechs are intercompatible and the chains are the same width so in theory, if your seven speed wheel fits in the frame and the distance between the smallest sprocket and the frame is the same as your 8spd wheel it'll work. Just don't shift to the bottom gear!!