Tirreno Tech: what are the wavy rimmed wheels Ineos used for the time trial?

Tirreno-Adriatico drew to a conclusion with an individual time trial on Monday, with Simon Yates' emphatic performance sealing the overall in this year's race. But from a tech point of view, the biggest news was Ineos Grenadier's rather unusual wheel choice, seen under Geraint Thomas, Chris Froome and stage winner Filipo Ganna.

Whilst the rear wheel of their Pinarello Bolide TT bikes - barring Ganna - look to be an on-sponsor Pro Textreme Tubular Disc wheel, the front wheel choice is anything but. With its unusual wavy rim profile and alternate spoke pattern, it's unlike anything available to Ineos from Pro. So what is it?

Well a little bit of digging and it turns out to be a wheel from a lesser known brand called Princeton CarbonWorks. As the name suggests, it's a US company founded by aerodynamic and mechanical engineering graduates from the renowned Princeton University.

A little more digging shows that the wheel is the front wheel from its Wake 6560 set. However to make things even more interesting, the wheel isn't the most recent iteration but rather an older model. So why are Ineos Grenadiers using an out of date wheel for time trialling?

It turns out that the Wake 6560's rim shape has been designed to mimic the aerodynamics of a deeper section wheel with the shape alternating between 60mm and 65mm in depth. The rim contains '24 sinusoidal oscillations' and is designed to reduce drag and diminish the effects of 'vortex shedding'. Vortex shedding can, when tuned correctly (hence the rim oscillations) potentially provide small accelerating forces that could potentially see a performance impact.

It was probably the potential gains of this rim shape combined with a desire to reduce the impacts of any crosswinds found on the coastal TT course that led to the use of the wheels.

As to the reasons for the use of the older model? It looks like the older version utilises less spokes so potentially is lighter and even less impacted by crosswinds, and any potential stiffness deficiencies are negated in a time trial.

Ganna went one further and also opted for Princeton Carbon Works Blur 633 rear disc wheel to complete the package. It must have worked as he stopped the clock with the fastest time of the day to bring a much needed stage victory for Ineos.

Curiously current ITT world champion Rohan Dennis, a rider notoriously picky with is equipment, opted to stick to using a Pro tri-spoke front wheel.