Ah - yes - I meant wheels. Both sets of Wheels are 700c. They have different width rims though which is why I want to swap.

So - I'm looking to take a wheel that has an 11-speed cassette and put a 7-speed cassette on it. Can I do that or do hubs have specific speed cassettes they are compatible with?

I was thinking about just putting the wheel with the 11-speed on, but another poster said I would run into trouble with my rear derailleur...

After all of this - I have to buy a new chain anyway. So I'm looking for advice from all of you so I can get a good set-up, then buy the appropriate chain!