Originally Posted by
MinnMan
If you just want a spare wheel to make swapping between outdoors and indoors earlier, there's no reason to by a whole wheel set. Rear wheels are sold separately. Just remember that you'll also have to buy a cassette that fits your derailleur. And if you don't want to adjust the derailleur each time you swap wheels, you'll want it to have the same set of cogs as your current cassette.
+1
Just a cheapo rear for the trainer is all you need.
IF you bought an "identical" wheel/cassette to what you currently have, you'd still probably have to tweak the barrel adjuster a bit.