Aerodynamics have become the integral factor in bike and component design over the last three decades as manufacturers chase drag-reducing credentials that leave the end user with more propulsion from their power output.
Until recently, tyres had been overlooked in this constant pursuit of free watts. But as one of the surfaces that creates translational (front-on) drag, it was ripe for optimisation.
Last year’s launch of the Continental Aero 111 realised the potential of rubber. A front-only tyre developed in collaboration with aerodynamic expert Swiss Side and wheel specialist DT Swiss, the tread includes 48 small square cavities that generate vortices. The result is a managed airflow turbulence over the front wheel that maximises the sailing effect of the wheel’s rims, lowers drag at a wide range of speeds and improves handling in crosswinds.
While DT Swiss were integral in the tyre’s development, and optimised the whole system based on their second generation ARC range’s rims, they knew that there was even greater potential. Rather than resting on their laurels, they reinvented the wheel – literally – to create the ultimate aerodynamic system.
The shift in preference amongst amateurs and professionals towards wider tyres meant that a 20mm inner rim was no longer enough. DT Swiss say that increasing the width to 22mm works hand in hand with the aerodynamics of a 29mm AERO 111 tyre, but it will have several other benefits for the end user. A wider inner rim equals an increase in the tyre’s inflated width and surface area, allowing for lower tyre pressures – boosting rolling resistance, grip and comfort on a smorgasbord of road surfaces.
Increasing the inner width set in motion a chain of events that saw the whole rim’s structure redesigned. While a 22mm inner width was good for the tyre’s aerodynamics, it was bad for the rest of the wheel, increasing the drag of the older, U-shaped profile. To negate the impact on the frontal area, the U was swapped for a V, which DT Swiss claim compensates for the increased base drag, while also improving handling and a smooth steering sensation.
However, an aero rim and tyre that work together in tandem will only get you so far. To truly maximise their benefits, the whole wheelset needs to be considered in pursuit of the wind-cheating goal.
To that end, DT Swiss lace each rim with aero-optimised spokes, while the front wheel has been reduced to 20 count – decreasing rotational drag and saving weight. Slightly higher rim profiles (55mm, 65mm and 85mm) across the three-strong range have decreased the length of the spokes, reducing drag even further. The results speak for themselves, with in-house wind tunnel testing of the third generation ARC 1100 Dicut DB 55 showing a reduction in rotational drag of 5.5 per cent at zero degrees yaw and 12 per cent at 10 degrees yaw when riding at 45 kilometres per hour compared to the second generation ARC 1100 Dicut DB 50.
The launch of the Continental AERO 111 also heralded the arrival of DT Swiss’s Wheel Tire System (WTS) – where a rim would be paired with a particular width of the AERO 111 tyre (26 mm for the new ARC 85 front wheel; 29 mm for ARC 55 & 65 as well as the Endurance Aero range) to take the wheel’s aero-optimisation to the next level. Any wheel featuring WTS would also arrive as a complete wheelset with mounted tyres, reducing assembly and prep time for riders.
Rather than settling for a new tyre on an older rim, the third generation ARC wheels are the first that have been developed with WTS in mind. In addition to the lower base drag from the V-shaped profile, there is a stronger sailing effect when used with the AERO 111 tyre. Steering predictability has also been improved with an even increase (and no jolts) in crosswind conditions. And when combined, the result is increased confidence to stay aero – and fast – at all times.
