That's funny. I was just riding my commuter bike yesterday and remarking to my wife how it was funny how much slower I am on it than on my road bike. I assumed

That's funny. I was just riding my commuter bike yesterday and remarking to my wife how it was funny how much slower I am on it than on my road bike. I assumed it had to do mostly with my aerodynamic profile and to a lesser extent what muscle groups engage when pedaling from a more upright position. The commuter is running Marathons in 32c and my road bike has Continental gp5000s :) likely a 30w difference when multiplied out for 2 tires. At a cruising effort where I'm doing perhaps 120-140w, that's huge! And it reflects where you're doing 12mph instead of 17mph.