A vortex of controversy: The backstory on Team Sky’s new aerodynamic skinsuit

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At the start line for Saturday’s time trial in Marseille, all eyes will be on race leader and three-time Tour de France champion Chris Froome, poised to take his fourth Tour title in five years.

Yet another Team Sky rider to watch will be Michal Kwiatkowski, who will be wearing the team’s new and controversial Castelli Aero Skinsuit 4.0. Castelli’s new skinsuit caused a stir during the Stage 1 time trial in Dusseldorf, when several team managers, including a particularly vocal Marc Madiot of FDJ, suggested that Sky broke UCI rules regarding items that are designed specifically to enhance performances by changing body shape.

Froome wore the skinsuit on Stage 1, but he won’t be wearing it Marseille, not because he doesn’t want to but because Tour de France rules dictate he can’t — all classification leaders are obligated to wear clothing supplied by ASO’s clothing partner, Le Coq Sportif. Yes, that includes skinsuits.

When quizzed about the Castelli skinsuit and the fact that he’d not be wearing it in the final time trial, Froome didn’t seem too concerned. “I’ve ridden in the skinsuit provided by the race organisers almost every year I’ve won the Tour, and it hasn’t been a problem, at the end of the day it’s all about the legs.”

All very true, yet very surprising considering it comes from a rider whose team coined the term “marginal gains.”

Though not as technically advanced as the Castelli version, the Le Coq Sportif skinsuit is still custom made for the GC leader. While most riders were relaxing as much as possible on the night prior to the final time trial, Froome had one extra task — a fitting with Le Coq Sportif.

Though most of the major contenders are measured by Le Coq well in advance of the race, the riders in leader’s jerseys are fitted the night before the final time trial. Tailors then work throughout the night, preparing a perfectly custom garment for the GC leader to roll out in on Stage 20.

Team Sky’s partner in speed

The 2017 Tour has been a bit thin for time-trial action. Race organisers ASO limited the race to two short individual races against the clock, Stage 1 in Düsseldorf and Stage 20 in Marseille.

Stage 1 was a short, punchy 14km effort held in pouring rain which saw action, carnage and controversy. Alejandro Valverde (Movistar) crashed out in spectacular style, breaking his kneecap. Orica-Scott ace Luke Durbridge also fell victim of the wet weather and slippery roads. The Australian didn’t just break his shoe in half, he damaged his ankle severely enough to see him pull out a short 20km into the following stage.

The biggest controversy in Düsseldorf wasn’t related to the weather, but rather Team Sky’s Castelli Aero Skinsuit that caught the headlines — and had Marc Madiot suggesting the team had broken UCI rules.

Castelli became the official clothing sponsor of Team Sky at the start of the 2017 season. Previously the Italian brand had worked with the several incarnations of what is now Cannondale-Drapac, and also the original Cérvelo TestTeam. With both of those teams, Castelli developed apparel that had a significant impact on the market and what riders use in races, such as the Gabba, a wet weather jersey, and the San Remo speedsuit, a skinsuit used for all-day racing.

Now, with Team Sky, Castelli was again in the limelight with a product that could see other brands chasing the same technological advancements.

Team Sky’s Geraint Thomas rolling out of the start gate in Dusseldorf; he would go on to take the stage win.

Why all the fuss?

Now, with the dust settled, Castelli’s brand manager Steve Smith can look back on the controversy with a chuckle.

“Actually, we’re a little bit surprised that it caused that much controversy,” he said. “The stuff they’re complaining about is similar to things used by other teams already. But I have to thank Marc Madiot publicly for bringing it to the attention of everyone. So it’s been good for us, it’s been good publicity.”

Several teams, including Movistar, have clothing with a similar dimpled pattern on specific areas of the kit. It’s been spotted on several items of Movistar’s road team line that Endura produces for the team.

The dimpled pattern, usually printed onto the fabric, is designed to disperse slow-moving air by creating vortices, and to keep faster-moving air closer to the body surface for longer.

The development of the new suit has been over a year in the making. Talking with Smith, it would seem the suit is actually a whole new item rather than a refinement of previous skinsuits.

“We had to kind of reinvent everything we knew about skinsuits, and so it’s actually a lot more revolutionary than what it looks like,” he said.

Beyond the vortex-generating dimples, what we gathered from Smith’s sheepish answers is that the suit is actually made of multiple different materials that play different, specific roles. However the technology behind the suit isn’t something Castelli is keen to expand on.

Froome in full flight during Stage 1 of the 2017 Tour de France.

In the tunnel

One might imagine that having the rider whom the suit is being designed for on hand for wind-tunnel testing would be an ideal scenario, but surprisingly it’s not always the best route. According to Smith, using a mannequin produced from a 3D body scan of Froome was more than adequate when testing the prototypes.

“If you’ve ever actually worked in a wind tunnel, it’s ugly,” he said. “Sometimes we avoid taking the actual dedicated person in there, because there’s so much trial and error. It can make them kind of lose confidence in the process.”

With seven or eight people working on the project, Castelli instead worked with other riders, professional and amateur, delivering a near-final product for Froome to test at a mid-season training camp. There he could get a feel for the results firsthand, without the muddied backstory of the previous iterations of wind-tunnel hits and misses.

The skinsuit is fast — if the rider is fast

Any piece of equipment used by the peloton, UCI rules dictate, must also be available to the public. Just take Team Sky bike sponsor Pinarello and the custom handlebar and stem that Froome has been using the past few seasons on his TT bike, the Pinarello Bolide.

The Italian bike manufacturer only announced in the last week that they will now be making commercially available the 3D printed titanium cockpit. Customers wanting the cockpit will have to go through a body scan before waiting 90 days for a final delivery.


Mikel Nieve was using Castelli’s older TT suit, a vastly different design when compared to the new version.

To comply with UCI rules, Castelli will also have to make their skinsuit available to the general public, but Smith insists that most not-so-fast riders will want to stay away from it. Castelli’s wind-tunnel testing shows that the suit performs better at higher speeds — and not so well at the speed an average amateur could hold in a time trial.

“They won’t be custom made,” he said. “And to be honest, it won’t really do much for the rest of us.”

As for firm numbers on wind-tunnel testing, Smith was very tight lipped. “You know, the way it works so complex, there’s not really a number that we’re going to throw out there.”

Will we see any extra dimples on this version? Smith hopes not. Even when asked for photos of the skinsuit for this article, Castelli wouldn’t oblige.

“We’re keeping it away from getting too many close-up shots,” Smith said. “We’re going to try to keep this advantage for as long as possible.”

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