Race tech: Rabobank's time trial wheels at the Giro d'Italia

Shimano hubs laced to HED rims for races against the clock

Rabobank riders arrived at the Giro d'Italia time trial kick-off with three different types of carbon aero wheels – 50mm and 70mm deep aero options, plus a new time trial disc built with internal spokes - all conspicuously badged with giant "PROtotype" decals. Upon closer inspection, though, it turns out that the team was instead using wide-format Stinger carbon tubular rims from US company HED laced to Shimano hubs, all in the aim of reducing drag for more of a competitive edge.

The key feature of all three new wheels is their rims: all sport wide tire beds and brake tracks, which offer more support to the tire along with improved aerodynamics (because of better tire interface and blunt trailing rim edge). Rabobank mechanic Joost Hoetelmans estimated the new rims’ width at 25mm – in reality they're more like 28mm at their widest point.

Right now the team are primarily using the specially built wheels for time trials. All of the Rabobank riders started the first road stage on Shimano-branded 50mm and 35mm wheels. The two new road wheels sport straightforward builds, with 18 front spokes and, presumably, 24 rear spokes – rear wheels weren't available for our inspection.

The spokes are bladed and connect to the rim via standard external nipples. Both wheels rely on standard flanged Dura-Ace hubs. The wheels are Shimano-built and came to the team assembled. While seemingly pedestrian, the hubs sport Shimano’s much-loved angular contact bearings and ‘digital’ detented adjustment system, as well as a titanium cassette body.

The 70mm model looks deep and fast but also very wide

The most interesting of the new trio is the disc, again based on HED's Stinger model. It’s built using the 70mm rim laced via standard spokes to the same, standard Dura-Ace rear hub as the road wheels. However, it’s then finished with a carbon cover that runs from the hub up to the rim, where it’s connected to roughly 1cm of the inner surface. This is done on both sides.

Hoetekmans said the design makes for an extremely light and stiff wheel. He didn’t have information on the build process or what rebuilding the wheel entails, although it clearly requires tire removal to access the rear of the nipples.

We weren’t able to weigh any of the new wheels on our scales, but swapping in the Shimano Dura-Ace hubs should only add a few grams to the stock HED versions, which weigh 1,339g for the 50mm wheels, 1,506g for the 70mm set, and 1,130 for the rear disc.

The rear disc is based on HED's Stinger model

New rubber for Rabo’s prototype wheels

Along with the new wheels, Rabobank were seen on an entirely new Vittoria Corsa Evo SC tire, with SC standing for Servizio Course or service course. Hoetekmans said the tire uses a tread similar to the storied Clement Criterium, but made from a new ISO dual (center and side) compound. This is said to offer the best grip in the line, as well as roll extremely fast. However, Vittoria admit it also wears fast.

The tread is hand glued to Vittoria’s natural colored CoreSpun 320tpi casing, in a 23mm width rather than the 21mm traditionally used for all-round road race stages. The CoreSpun casing threads have a poly core that’s wound in cotton to remain suppler than a solely synthetic casing. The tire is currently only available in a 23mm width. Claimed weight is 250g.

The team were using the new tire in a larger width on the rear disc wheels for the opening time trial, as it fits the wider rim, both in terms of handling and aerodynamic performance, much better than a smaller tire.

Rabobank is using unusually wide 23mm tubulars for the time trials to better match with the wider rims

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