MAKING SENSE OFTHE RESULTS

► REAL-WORLD TESTING can produce some messy data, but it beats making assumptions. Plus, we had Josh Portner at our disposal as an expert resource. Josh is a true tyre nerd and the former technical director at Zipp. He currently owns the premium accessory brand Silca and runs a company called Aeromind,

which offers various consulting and testing services in the areas of aerodynamics, tyres and tyre pressure for pro cycling teams.

We shared our testing and data with Josh, and he spent some time walking us through making sense of it. The first thing that surprised us was that in both tests, the fastest set-ups used what we considered to be relatively high pressure, 90F/95R.

Josh said, "On some level, that doesn't surprise me. We've spent 10 years convincing people to lower their tyre pressure. Now with a company like Zipp only allowing a max pressure of 72.5 psi (5 bar) in their wheels, it feels like the pendulum has swung a bit too far in that direction. We have people come to us and say things like 'Your tyre pressure calculator recommended 90', and they think that's too high. But the reality is that it's all about the surface you're riding on.

" The long-held belief that the higher your tyre pressure, the faster you go is true only to a point. Josh refers to that point as the 'breaking point'. Up to that breaking point, your rolling resistance will decrease if you increase tyre pressure, and that relationship is linear. But once your tyre pressure reaches the breaking point for a given scenario, the relationship becomes exponential in the other direction.