I put the 18 on my Speedmaster about 4000 miles ago (2 months) and I've never been happier. I haven't noticed any significant loss on the low end and I don't think I'll ever go back to the 16. I was shifting all the time with the 16. The range on the 18 is so much better for my style of riding (quick take-offs and highway cruising around 85-90).
