Tour de France 2025 - Stage 3: Valenciennes - Dunkerque | 178.3 kilometres | 800 vertical metres
The end of the third stage is just made for a bunch sprint: perfectly flat, almost straight except for a slight right-hand bend a good 200 metres before the finish, six metres wide. However, it will probably not be a real bunch sprint, as the Côte de Cassel (2.3 km, 3.8%) stands in the way of the sprinters 32 kilometres before the finish. It's quite possible that the peloton will break up into groups here and that a reduced field will sprint. The wind could also play a role on the approach to the finish, as the race heads towards the sea.
If there is a strong wind, a motivated team can initiate a wind edge race. The riders stagger across the width of the road to maximise the slipstream. The key to the success of the wind relay, however, is the will to collectively ride at full throttle. The man at the front has to go full throttle, i.e. pedalling 600 watts or more in the short lead, in order to reach speeds of 50 km/h or more in the wind.
Chasers only stand a chance if they organise themselves as a relay team - and go for it too. However, motivation is usually not as high in a group that is thrown together as it is in a team that acts as one. And space for a relay team is limited. A large group therefore usually breaks up into several squadrons.
Material for the wind edge
What does that mean for the choice of materials today? Aero bikes are the order of the day, as are aero accessories. The racers wear one-piece racing suits, aero helmets, some even time trial helmets. Aero socks, half-calf length at most, as prescribed by the regulations, tight gloves, maybe even aero overshoes. Each of the details in itself doesn't make a huge difference. But the sum of the details does. The fact that the speed is so high today is also due to the fact that the riders are much more streamlined than in the days of flutter jerseys and wide handlebars.
But if you reckon with the wind edge, you can do even more in detail. The front wheels in particular play an important role, as they are the sails of the road bike. In extreme cases, they can even generate propulsion in crosswinds and are also crucial for handling. How much wind pressure can be felt in the steering and how predictable the forces are depends on the shape of the rim and the interaction between rim and tyre.
If the pairing works well, the handling is less twitchy. The Conti Aero 111 tyre has a special tread pattern that ensures that the airflow stays on the tyre for longer and fewer pressure fluctuations are felt. TOUR has tested the tyre with various wheels and was able to confirm what the manufacturer promises: the riding resistance is reduced and the handling is improved. With the aero tyre, the bike is more stable in gusty winds.
A team that consciously plans the wind edge therefore has the material to make the most of the situation.
Our simulation today centres on the question of how much time the aero bikes make up on flat, fast sections compared to conventional bikes. We choose the ten kilometre long, flat segment on the approach to today's finish.
Number of the day: 23 seconds
A lightweight bike without any special aerodynamic attributes will lose 23 seconds over ten kilometres in the final. Anyone who has plans today and doesn't have the motor reserves of a Tadej Pogačar will therefore, from a rational point of view, do everything they can to be as streamlined as possible at the start of the stage.
The (almost) entire field at a glance*
The simulation of ten flat kilometres offers no surprises: On flat terrain, aero bikes have the tyre in front. The slowest bike loses 23 seconds over ten kilometres.
*) The calculations are based on the bikes tested by TOUR in the laboratory and wind tunnel. The bikes at the Tour de France may differ in some details. Of course, we have not yet been able to analyse last-minute prototypes. Background to the simulation.
Our expert
Robert Kühnen studied mechanical engineering, writes about technical and training topics for TOUR and develops test methods. Robert has been refining the simulation calculations for years and they are also used by professional teams.
