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Aerodynamics - disc wheel

As part of the 2018 rim redesign, we wanted to bring tubeless technology to the Parcours Disc.  In order to do so, we have reworked the entire wheel profile, to also allow the use of a wider, 25mm tyre.  With an internal width of 19mm, the new Disc allows riders to choose to run a lower tyre pressure, giving a smoother, more comfortable ride whilst also reducing rolling resistance.

We took a production prototype to the wind tunnel to compare the new tubeless-ready Disc to the older model.

Drag chart - Disc comparison

Learn more about how to interpret a drag chart here

Our results show that, when a weighted average taken across the yaw angles tested, there is no material difference between a 23mm and 25mm tyre (<1s/40km).  However, the tubeless-ready Disc was 4s/40km faster than the older model.

When scaled up to a full-Ironman distance (180km) ride, the comparison in time savings (when paired with a Chrono front wheel) is:

  • Prior generation Chrono/Disc raceday setup: 5min 37s
  • Tubeless-ready Chrono/Disc raceday setup: 6min 21s 

Note that these time savings are shown before accounting for the benefit of running a wider and/or tubeless tyre.  The reduction in rolling resistance has been widely-accepted.  Additionally, a wider tyre allows for a lower tyre pressure, increasing ride comfort.

Test protocol

  • Individual wheels only were tested
  • Each wheel was tested from 0-20 degrees of yaw, at 2.5 degree increments
  • Positive yaw angles cover non-drive side
  • Each test sweep was conducted twice, with results averaged
  • Test wind velocity at 30mph
  • Two Schwalbe One tyres were tested: 23mm and 25mm, both inflated to 100psi (consistent with previous testing)

Note: we did not remove tare (i.e. subtract the drag from the wheel clamp) for two reasons:

  1. In real-world riding, the wheel will have the frame supporting it
  2. As the wheel is rotated into the wind at higher yaw angles, one of the clamp posts will become increasingly “hidden” from the wind. Subtracting a simple tare value could therefore be misleading at higher yaw angles

The wheels we tested were:

  • Rim brake
    • Parcours Disc solid rear wheel (2017 model)
    • Parcours Disc solid rear wheel (2018 tubeless-ready model)

    Note: the same Shimano RS11 wheel was used as a benchmark for time savings rather than the commonly-used Mavic Open Pro box rim with a 32 spoke count. We believe this is more representative of the real-world benefits you will see from an upgrade.