I'd also like to know about the spacer. I've currently got a 130mm wheel with an standard-range 8-speed wedged into my old Schwinn with 126mm spacing. However, today I found that I couldn't get into the two biggest cogs in the back, no matter how hard I tried or what chainring I was in on the front. Does this have anything to do with needing a spacer, or is it soemthing else entirely?
Really frustrating. Hope this is relevant to the thread.