How fast do they go down the hills? I'm north of 250 and can only hit a hair above 52mph coming down a 1-mile stretch at 8% or so (coasting only). But I can pedal my 53x11 down a hill around 42mph or more (too much more & I start bouncing). Have you tried pedaling?

(I figure since they don't take it easy on me up the hills, I make them work going down. They can draft all they want, but at some point, they can no longer keep up unless they pedal while I'm freewheelin'. )