Tour de France 2025 - Stage 4: Amiens Metropole - Rouen | 174.2 kilometres
The sawtooth profile of the fourth stage has a good 2,000 metres of elevation gain in store for the riders, with the difficulties increasing towards the end. Six kilometres before the finish, the Rampe de Saint Hillaire rears up with a 15% gradient, followed by a short stretch of deceptive flat terrain. Then it's a steep descent to Rouen, where a 500-metre-long final climb with a 5% gradient must be mastered before the last few metres lead flat to the finish.
Many race scenarios are conceivable, but a mass sprint is certainly not one of them. Whether stage hunters or GC riders, both are faced with 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 a sprint at the beginning of the steepest section of the final climb. Our model rider, in this case the favourite for the overall classification, Tadej Pogačar, starts the simulation at 35 km/h - uphill, of course. At the end of the climb, Pogačar would be one tenth of a second ahead of his aero bike Y1Rs with the lighter V5Rs, which would correspond 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 as much as one second according to our calculations, which corresponds to a gap of 5 metres. Anyone planning to attack on the steep section would be well served by a lightweight aero all-rounder or even a pure lightweight bike. 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 in 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 equipment. Over a longer segment of the course, aero bikes push ahead. When considering equipment, it is therefore important to narrow down where and how the decision will be made and how the equipment can help make a difference.
An overview of (almost) the entire field*
The simulation of the steep section of the Rampe de Saint Hillaire shows: when it's really steep, weight is what counts. The lightweight aero all-rounder Tarmac SL8 climbs the fastest by combining minimum weight and good aerodynamics.
*) The calculations are based on the bikes tested by TOUR in the laboratory and wind tunnel. The machines used in the Tour de France may differ in detail. Of course, we were not yet able to examine last-minute prototypes. Background information on the simulation.
Our expert
Robert Kühnen studied mechanical engineering, writes for TOUR about technology and training topics and develops testing methods. Robert has been refining the simulation calculations for years, they are also used by professional teams.
