Rohan Dennis BMC TM01 TimeMachine ATOC-feature
  • Arfy

    So 22mm’s are back, wider tyres are out. Was there a flaw in the ‘science’ of wider tyres?

    • woodsy

      i wouldn’t be suprised if it was a clearance issue with a TT rig

    • Terence the Tractor

      The tyre width is an aerodynamics based decision, the HED trispoke is still only 19mm and they advise a 21mm tyre width. Since aerodynamic drag at 50kph makes up more than 80% of the resistance it makes sense to give up a little rolling resistance for a bigger gain against drag.

      Its worth noting that even Zipp with its wide rims still only advise 23mm tyres for the best aerodynamics.

      • Arfy

        As sensible as what you say is, compare Rohan’s setup to Bookwalter’s from just two years ago with 25mm tyres:

        Something’s changed dramatically in the philosophy of aero wheels!

        • Terence the Tractor

          I think it is just the different philosophies for different wheels. The H3s are a very successful, much older design than the Shimano C75s (the H3 helping the Texan with no name not win the 2005 Tour). The C75s are 5mm wider than the H3s and have a recommended 23-25mm tyre width (around 5mm more).

          I believe it is mainly to do with providing the roundest nose profile without producing a ‘lightbulb’ effect, which increases drag noticeably, so the wider the rim, the wider the tyre, to a point. Enve curiously recommends 25mm for the SES 4.5 and 23mm for the rest of the SES range. The majority of wider modern rims recommend 23-25mm.


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