I went from 48x16 to a 48x17 (for more skid patches) and for the longest time I thought I was going a lot slower. Well, I was going a lot slower. It felt very spinny to me for a long time. I would say my average speed went up, though, because I could stop faster and was less wary of getting up to speed. Anyway, the last couple weeks I've been getting really fast on that gear. I was always thinking about my pedal stroke and forgot how to really power the cranks. I could spin em no problem, but it seemed I would just spin out. I've been riding with a friend who is much stronger than me and it forces me to pedal harder and I'm going a lot faster now that I can try to mix good pedal rotation and power. There is a speed limit sign that has a radar thing that tells you how fast you are going and I used to top out around 24 (going downhill) because the lower gear felt so spinny but lately it's no problem for me to get into the mid 30mph range. I think I have hit 30 on a flat a few times too.