Testing times

Swiss Side’s testing followed a protocol intended to maintain the focus on the performance of the wheels. To this end, Ballard and his colleagues began by placing only the front wheels in the tunnel’s test section, before moving later to a complete bike, and finally to a bike ‘ridden’ by a half-dummy: a mannequin with a lower torso and legs capable of simulating a pedalling action.

“Our target was to determine at what stage the representation becomes too complicated,” Ballard explains. Over-complicate the process with, say, the introduction of a human rider, or a complete, static mannequin, and repeatability becomes an issue, he suggests. “The slightest movement you can get from the rider or the dummy can cause large differences in drag, and completely swamp the small measurement differences you’re looking for,” he says.

Ballard’s team began testing with the knowledge that Zipp’s 808 “was the wheel to beat”. The Swiss Side team had been impressed by its characteristics in side winds and its ability to delay the stalling point, an effect that in certain conditions can create thrust. “We were targeting that sort of response from the Hadron wheel,” he says.

The results of the test compared favourably with Zipp’s well-respected offering, Ballard claims. “Directly compared to the 808, we were matching the drag figures very, very closely, so within one or two per cent through the cross wind, yaw angle range,” he says. Additionally, its lower, 62mm profile incurred a lower increase in the drag typically encountered when a wheel hits its ‘stall’ angle.