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Our deep section rims are made to the latest U section profile to cope with airflow from all wind angles and still provide aerodynamic advantage, unlike other dated and cheaper V section rims that are still widely available, that are usually very unstable in gusty conditions.
Our rims are also designed with an angled braking surface to direct the airflow from the tyre nicely to the main rim section to create an overall combined tyre/rim profile.
The new Walker Brothers Ethereal Disc wheels, coming to market in March, are lenticular in profile which suits the enviroment of the indoor Velodrome. In a series of independent aerodynamic and performance tests, the new prototype Ethereal track disc wheels have come out consistently faster than Mavic Comete wheels.
Meticulously tested by Dan Bigham from Watt Shop at Derby Veledrome against the Mavic comete and Corima wheels, the Ethereal proved significantly faster in all tests.
Aerodynamic testing of all wheelsets was performed by WattShop at Derby Velodrome. All wheelsets were fitted to a Planet-X Koichi San II bike, size 54cm. Data was collected using a Quarq Dzero crank based powermeter. Drivetrain setup was 61x16 Pyramid Design PEEKrings and cogs, with a WattShop treated KMC X101 chain, these minimised drivetrain losses as well as kept a more consistent chain tension. Chain tension was set as close as possible across all wheels, and was kept as loose as possible to minimise any variations due to chain tension. All wheels were fitted with Vittoria Pista Evo CL tyres with the exception for the Walker Brothers Ethereal front disc which had a Vittoria Pista Evo CS tyre due to tyre availability issues at the time of testing. This Crr variation was accounted for with the Crr testing. All tyre pressures were set at 220psi using a Lezyne CNC Floor Drive pump. Each wheels rolling resistance coefficient (Crr) was then calculated on rollers using the Tom Anhalt roller method (http://bikeblather.blogspot.com.es/2013/02/tire-crr-testing-on-rollers-chartand.html)
Prior to each test run, total system mass was measured on Withings WS-50 Scales. The weighted rear tyre circumference was measured prior to each run to eliminate any circumference variations affecting velocity measurements. Air density was calculated from ambient air temperature, air pressure and humidity.
Each test run was performed at 56kph for approximately 4 minutes on a clear and empty velodrome. The data was then processed in MatLab, using an energy balancing equation of motion in order to calculate the instantaneous CdA for each second of the test run. This was then averaged across the entire test run to give a CdA value for that particular setup. The data is presented below.
Test Run 1.
Test Run 2. (rear wheel only)
Walker Brothers Ethereal 0.1815m^2 CdA 453.8w @ 56kph
Mavic Comete 0.1832m^2 CdA 457.4w @ 56kph
Corima flat profile 0.1844m^2 CdA 459.9w @ 56kph
Test Run 3. (Front wheel only).
Walker Brothers Ethereal 0.18216m^2 CdA 414.6w @ 56kph
Mavic Comete 0.18411m^2 CdA 419.0w @ 56kph
Corima flat profile 0.18632m^2 424.1w @ 56kph