What wheel size, how many teeth on the rear sprocket, how many rpm's is the engine running?
My bike has a 26x1.75 tire, 44 tooth rear, and runs about 23mph at 5500rpm. Sure, it can rev a bit higher but the vibes start to get excessive. The speed is as read by a Schwinn computer and the revs are as read by an ENM PT16e2 rev & hour meter. I know it could go faster with fewer teeth on the rear sprocket, but we have big hills here and I don't want to give up the hill climbing ability. I'm not sold on any of the existing gear change products but eventually someone will crack that problem with a compact, reliable and fairly priced product. That's the holy grail.