Tour tech: Finding and fitting the perfect skin suit for Team Sky

by Caley Fretz


Castelli isn’t quite sure why the sheer, smooth fabric that will stretch over the shoulders and backs of Team Sky riders in Monday’s team time trial is so fast, they just know the wind tunnel says it is. It’s certainly unique, like stretchy, thin silk. The company went through thousands of fabrics and dozens of iterations of a new skin suit for the team and found something it says saves five to six watts compared to last year’s suit.

Castelli provided CyclingTips with a sneak peek of the suit, called the Body Paint 4.2b, late last week, out of the back of a van at a team hotel. The white fabric that sits on the arms, shoulders, and back has an interesting feel, close to silk, but with far more stretch. It’s thin, translucent, and soft to the touch. Castelli’s Steve Smith wouldn’t name the specific fabric.

The suit replaces a controversial skin suit that Castelli believes was about to be banned by the UCI for its use of “pimples” (not dimples because they push out rather than in, according to Castelli) across the shoulders and arms. That suit created controversy last year when it was debuted in the opening time trial, where Castelli claimed it was worth more than 10 seconds on the short, 14km course.

FDJ filed a formal complaint, alleging the suit ran afoul of UCI rule 1.3.033, which bans “non-essential items of clothing or items designed to influence the performances of a rider such as reducing air resistance.” The wording of the rule allows for such items if they are integral to the structure of the clothing, and thus essential. Sky argued its pimples were structural.

Smith met with UCI technical coordinator Jean-Christophe Peraud a number of times about the new suit and it falls on the right side of all UCI regulations.

Team Sky Skinsuit 2018 Tour de France (1 of 1)

There are few places in cycling where such tiny details matter as in a team time trial. Speeds and stakes are both high. Castelli began development of the new suit before last year’s Tour ended, with a meeting after the Marseille time trial on the penultimate stage.

This year’s particular TTT is somewhat exceptional, mostly for the speeds riders will hit. Drag is proportional to the cube of speed — riding twice as fast requires 8 times more power — meaning high speeds make aerodynamics even more important than usual.

“This TTT is super super super fast. We had to change our parameters we’re trying to reach,” Smith said. The team and Castelli modeled the time trial and determined that average speeds could be close to 60kph (Smith wouldn’t provide a precise figure used for the modeling). “When they’re on the front they’ll be up to even 700 watts, when they’re on the wheels it’s down as low as 300.”

The development process was centered around finding the right fabric and then perfecting the fit. The fabric came out of months of testing. “It’s super fine, it has some special qualities when it hits the wind,” Smith said. “We went out and tried thousands of fabrics and combinations of fabrics. There are a couple diff fabrics on the suit, but the part that the wind sees is pretty special.”

Riders were first fit for their new suits at the end of last season, “because they do pack on a few kilos over the winter,” Smith said. That’s the baseline. Then as the Tour approached, Sky handed Smith a long list of 15 riders. Castelli caught up with each in the weeks leading up to the race to dial in a final fit.

Are there any riders who require a bit of extra tailoring? Well, Froome does.

“Everybody comments on how Chris looks a little funny on the bike, but Chris does actually have some strange morphological stuff,” Smith said. “His chest measurement is almost a size large for us, he has a huge huge lung capacity. And then his shoulder width is more almost between a small and an extra small. That’s what makes him fast, he has those tight, narrow narrow shoulders. All the great TT guys are able to get their shoulder down to the width of their body, and then he’s got huge lung capacity.”

“He changes shape quite a bit before winter Chris and [Tour Chris],” Smith continued. “Everything we give to him, we put in the date of when we did the fitting. He has about four different fits in his closet. He’s the only guy we’ve ever done that with. He will balloon up a bit.”

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