I changed from 17 to 18 on my America about 1500 miles ago. I like the highway and solo, but don't like riding 2-up near as much. The gears start getting a bit tall. I plan to go back to the 17 next month. I think there is a BIG difference each front sprocket tooth you go up. If you're running a stock 16/42 SM, you might find the 17/42 combo like the Americas have stock, just what you're looking for.