I'd say Calfee fat tubes, + Spinergy wheelset they are not a fast wheelset with those fat spokes would probably add up to 4/5 mph, having had the Spinergy's for less than a year & switching to WI M15 hubs with DT Aero lite bladed spokes & Hed C2 rim, results of at least 5/6mph faster on big drops in the 40/50mph range ,plus more power transfer.