Road cyclists have long taken as a given that, if you want to go fast, you need relatively narrow tires and high inflation pressures.

That convention is being turned on its head, however, with a growing trend toward wider casings and lower pressures, even among top professional racers — and it’s all being backed by some very sound science.

How wide and low should we be going, though, and what’s the reasoning behind the shift? To help shed some light on the subject, U.S. technical editor James Huang invited two of the industry’s top luminaries to this week’s CyclingTips Podcast.

On one end of this week’s roundtable discussion is Josh Poertner, owner of Silca and former technical director at Zipp. Armed with years of experience helping the world’s most elite teams and racers go faster over a wide range of terrain,Poertner has learned far more about wheel-and-tire setups than any of us knew was possible. Sitting opposite Poertner is Jan Heine, publisher of Bicycle Quarterly and head of Compass Bicycles, and the man who is largely credited for singlehandedly popularizing the grassroots wide-and-low road tire movement five years ago.

Can’t quite allow yourself to believe that a 30mm tire at 70psi might be faster than a 23mm one at 100psi? Okay, but do yourself a favor and have a listen to what Poertner and Heine say about it — and keep an open mind, because what you feel, and what the numbers tell you, don’t always go hand in hand.

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Episode 9 Direct Download