Why Visma's black Tour de France jersey will not make riders hotter

More than 100,000 supporters voted between two Gaudí-inspired special edition jerseys, with the black version narrowly beating a lighter alternative. The result soon prompted a familiar question: could a dark jersey absorb more sunlight and make it harder for riders to stay cool?

At the time, the discussion was largely theoretical. The latest forecasts have since added urgency, with intense heat expected to affect the opening week of the Tour. Organisers are preparing additional cooling and hydration measures, although major changes to stage times remain unlikely because of the security, broadcasting and logistical arrangements involved.

Mathieu Heijboer, head of performance at Team Visma | Lease a Bike, said the original concern was understandable.

“It is understandable that people think a dark jersey absorbs more heat than a light one,” Heijboer said. “Research in the past has shown that darker clothing can be warmer. But the textile industry in elite sport has developed to the point where much bigger differences can be achieved through the fabric itself.”

According to Heijboer, the structure of the material, its ability to release moisture and the treatment of its fibres have a greater impact on heat management than whether the jersey is black or white.

During a Grand Tour, riders must cope with prolonged exposure to sunlight, high temperatures and intense physical effort. The challenge is not only to limit heat absorption, but also to allow sweat to evaporate quickly.

“Ultimately, you want to prevent the body from heating up too quickly,” Heijboer said. “It also matters how fast moisture is removed. Does it remain in the jersey, or can it evaporate effectively?”

The jerseys use fibres with UV resistant properties, which can help reflect part of the incoming radiation rather than allowing it to be absorbed by the fabric.

That does not mean colour has no effect at all. Rather, the team’s position is that its influence is relatively small when compared with the technical properties of modern performance clothing.

Team Visma | Lease a Bike said it carried out several tests to determine whether the black jersey could create a meaningful performance disadvantage.

The trials included climate chamber testing in which solar radiation was simulated.

“We examined how quickly the temperature rises underneath a jersey,” Heijboer said. “We also carried out tests using mannequins that can sweat.”

According to Heijboer, the results showed that differences between fabrics were much more significant than differences between colours.

“All the results show that the choice of fabric plays a much greater role than the colour,” he said.

Additional tests were conducted during the development of this year’s jersey, with different combinations of colour and material compared under controlled conditions.

“Those tests confirmed what we already knew,” Heijboer said. “Fabric makes a much bigger difference than colour.”

The detailed results have not been published, which means the data and methodology cannot be assessed independently. The conclusion nevertheless reflects the growing importance of ventilation, moisture transfer, UV protection and fabric construction in professional cycling clothing.

Even if the black jersey itself is unlikely to create a significant problem, the expected temperatures could still influence the opening stages of the Tour.

Organisers can provide additional bottles, ice packs, shaded areas and neutral vehicles carrying cooling supplies. The UCI’s heat protocol also allows officials to consider shortening a route, neutralising part of a stage or making limited changes to start and finish times.

Moving stages several hours earlier would be far more difficult. “You can cut 15 kilometres or start half an hour earlier, but changes can only be made at the margins,” Tour director Christian Prudhomme told AFP.

Road closures, security operations, local authorities and live television schedules are arranged months in advance. ASO technical director Thierry Gouvenou has also stressed that organisers often have only a narrow window in which to respond, as reliable heat forecasts may not become available until a few days before a stage.

For the riders, the decisive factors will therefore be familiar ones: staying hydrated, keeping core temperatures under control and recovering quickly enough to do it all again the next day.