Tour de France 2025 - Stage 4: Amiens Metropole - Rouen | 174.2 kilometres | 2050 vertical metres
The saw-tooth profile of the fourth stage has a good 2000 metres of climbing in store for the riders, with the difficulties increasing towards the end. Six kilometres before the finish, the Rampe de Saint Hillaire rises with a gradient of 15%, followed by a short section of deceptively flat terrain. This is followed by a steep descent to Rouen, where a 500 metre long final climb with a gradient of 5% has to be mastered before the last few metres lead flat to the finish.
Many race scenarios are conceivable, but a bunch sprint is certainly not one of them. Whether stage hunter or GC rider, both face the same question again in this stage: lightweight or aero or both? Can an all-rounder like the Specialized Tarmac SL8 win the bike classification today?
We simulate an attack at the start of the steepest section of the final climb. Our model rider, in this case the favourite for the overall standings, Tadej Pogačar, rides quickly into the climb and attacks hard as soon as it gets really steep. At the end of the climb, Pogačar with the lighter V5Rs would have a tenth of a second lead over his aero bike Y1Rs, which corresponds to about half a bike length.
Number of the day: one second!
The Tarmac SL8, which weighs 6.8 kg according to our measurements last year, outperforms the most aerodynamic bike in the field, the van Rysel RCR-F Pro, by up to one second according to our calculations, which corresponds to a gap of 5 metres. If you want to attack on the steep section, a lightweight aero all-rounder or even a pure lightweight bike will serve you well. However, aero performance is helpful in maintaining the lead to the finish line. In such a scenario, a lightweight aero all-rounder that can do everything comes into its own.
After looking at the profile, Tadej Pogačar will certainly opt for the V5Rs and compensate for the aero deficits on the descent with technique and leg power.
A rider who approaches the race in the style of a breakaway has a less clear-cut situation when it comes to choosing a bike. On a longer section of the course, aero bikes have the edge. When choosing equipment, it is therefore important to narrow down where and how the decision is made and how the equipment can make a difference.
The (almost) entire field at a glance*
The simulation of the steep section of the Rampe de Saint Hillaire shows: When it gets really steep, weight matters. The lightweight aero all-rounder Tarmac SL8 climbs the fastest by combining minimal weight and good aerodynamics.
*) 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.
