Continental Aero 111 wind tunnel & rolling resistance data
The goal of this test was to evaluate the rolling resistance performance as well as the aerodynamic drag of Continental's new tyre, the Aero 111 against the Continental GP5000 TT. We also tested against a market leader in Crr/performance - a Vittoria Corsa Pro Speed.
We selected three tyres for this test - the Continental Aero 111 in 26mm, GP5000 TT in 25mm, and a Vittoria Corsa Pro Speed in 26mm.
Rolling resistance testing
For the rolling resistance test, all the tyres were mounted on a shallow section aluminium rim, with an external width of 24.7mm and internal width of 19.6mm.
The protocol was the same as our standard rolling resistance tests: we swapped between the tyres as a rider rode a bike on rollers, measuring power output and speed, as well as atmospheric conditions and bike/rider weight, repeated over a number of days testing. Crr was then calculated from this data to give a comparison value between tyres.
Wind tunnel testing
For the wind tunnel test, we mounted all the tyres on an AeroCoach Zephyr wheel, which is 78mm deep and has a 19.6mm internal width, and 26.7mm external width at the brake track, extending out wider further down the rim.
The Zephyr wheel was mounted in a Cervélo P5 disc brake time trial bike, with an AEOX Orbit disc in the rear and the wheels set to spin with no rider.
WIND TUNNEL
When interpreting wind tunnel results it is important to understand yaw angle weighting.
Real world cycling is affected by changes in wind speed and direction.
The angle of attack of the wind on the cyclist is referred to as “yaw angle”, and this is affected by four components - rider speed/direction as well as the wind speed/direction.
While cycling on the road, you will experience a range of yaw angles. Very high yaw angles are much less common than lower yaw angles, and this can be expressed as a weighting function - for example at 45kph you spend ~80% of your time at 7.5deg yaw or less. At <40kph this extends out to 10deg, and at >50kph you will typically see 5deg or less.
We tested the aerodynamics of the tyres at our typical test speed of 45kph. This allows us to get good clean data (compared with testing at lower speeds, where the resolution isn't as good) which can then be applied to lower speed calculations later. As an example, a 10w aerodynamic drag saving at 45kph is equivalent to 4.7w at 35kph.
WIND TUNNEL
The results from the wind tunnel testing are shown in a chart below. Only the front tyre was changed in this test.
At lower yaws (0-10deg) all the tyres are very similar in terms of aerodynamic drag. At 10deg there is a sharp increase (referred to as a "stall") in aero drag for the Vittoria Corsa Pro Speed 26mm tyre, making it less aerodynamic than the other two tyres.
The Continental GP5000 TT followed a similar drag pattern to the Aero 111, with a decrease in drag at the higher yaw angles, but the Aero 111 had the lowest drag of the test.
Using the yaw weighting function, at 45kph the Aero 111 was the most aerodynamic tyre, by 0.2w over the GP5000 TT, and 0.9w over the Corsa Pro Speed.
It should be noted that although the Continental GP5000 TT is labelled as 25mm and the Aero 111 as 26mm, the GP5000 TT measured up as ~1mm wider than the Aero 111 when inflated and installed.
ROLLING RESISTANCE
The Corsa Pro Speed was the lowest rolling resistance (fastest) tyre on test, requiring 2.6w less power output for a pair of wheels to travel at 45kph (1.3w for one wheel), 20.5w for the Vittoria Corsa Pro Speed 26mm vs 23.1w for the Continental GP5000 TT 25mm. The Continental Aero 111 had a higher rolling resistance, requiring 30.9w for a pair of wheels at 45kph (5.3w for one wheel compared with the Corsa Pro Speed).
In this test we explored combined aero & Crr performance for 3 tyres commonly used on time trial/triathlon bikes for best performance.
We found that when combined Crr along with aero, a Corsa Pro Speed was the best option, followed closely by a Continental GP5000 TT, and then by a Continental Aero 111, which was let down by higher rolling resistance than the other two tyres, even though the aerodynamic performance was marginally better.
We tested all these tyres on an AEOX Zephyr front wheel - this wheel was specifically designed to accommodate a range of tyre widths, makes and models, which may be why the performance is so close aerodynamically between these tyres of different constructions.
