45 km/h using 70 watts less than before: TOUR Tech Briefing – Stage 10 of the 2026 Tour de France

​From 4 July to 26 July, the world’s best cyclists will be competing in the Tour de France. Victory and defeat on the roads of France will be decided not only by the riders’ legs, but also by their equipment. The TOUR Tech Briefing for Stage 10.

Another stage favouring breakaway riders is on the cards: the tenth stage in the Massif Central has 3,900 metres of climbing in store for the riders. The climbs aren’t particularly long, but there are plenty of them. Ideal for strong riders with no chance of winning the general classification, as only they will be given free rein in breakaway groups.

Whether, in the end, a breakaway rider will be celebrating, just like Mathieu van der Poel on the ninth stage, or whether a battle between the GC riders breaks out on the spur of the moment will depend on how the race unfolds.

Will Tadej Pogacar use the many short climbs to extend his lead over the rest of the field? That will probably depend on how he feels on the day and how his team performs. The season so far has shown that Pogacar can make the most of any route to gain time on his rivals.

Aerodynamically dominant

Technically speaking, it’s all quite clear. The stages so far have shown, without exception, that aerodynamics play an absolutely crucial role. If four breakaway riders, as on the ninth stage, are able to keep the peloton at bay, it is only through uncompromising effort and by making the most of their aerodynamic performance. It hardly matters how many metres of climbing there are; the riders usually manage an average speed in the mid-40s. That means 50 on the flat. Anyone who cycles competitively knows how hard it is to ride that fast, even for a short while.

By far the largest proportion of riding resistance (around 90% on flat terrain) is due to air resistance. Of course, the professionals also have more sustained power than amateur cyclists. 30–50 per cent more power combined with significantly lower aerodynamic drag explains the striking difference in speed between amateur and professional cyclists. The fact that the professionals can maintain such high speeds is down to the balance between pedalling power and aerodynamics.

Aerodynamics are determined by three factors: the aerodynamic riding position, optimised clothing and a streamlined bike. If all three components are optimised, a rider today expends around 70 watts less at a speed of 45 km/h than a rider had to 30 years ago, when jerseys were still loose-fitting and bikes were less aerodynamic. A 70 W reduction in aerodynamic drag at 45 km/h translates to a gain of 3.5 kilometres per hour. As a result, today’s professionals only hit the ‘wall’ at around 50 km/h, where the air resistance – which increases sharply with speed – becomes very noticeable. For amateur cyclists, this speed is around 10 km/h lower.

Decision on the downhill section

Even in the high mountains, aerodynamics are indispensable these days. On the Tourmalet, Jonas Vingegaard lost more time on the descent than on the climb – that is, at very high speeds where aerodynamics come into play. Not because his riding position is poor or his equipment is substandard. His bike is one of the fastest in the peloton.

But Tadej Pogacar clearly had the upper hand. More power, a greater willingness to take risks and, presumably, a better ratio of driving forces to drag coefficient – which is the real currency on descents. The fact that Pogacar is slightly heavier than Vingegaard helps him on descents. A rider who is heavier, without substantially increasing aerodynamic drag, rolls faster downhill. This is because gravity acts as a driving force on descents. Small, delicate climbers, as well as tall, slender athletes, are at a disadvantage in this respect compared to more compact riders.

This is also clearly evident in the case of Remco Evenepoel, who easily made up the seconds he had lost on the climb up the Tourmalet as he descended, and rolled back to join the group with Florian Lipowitz. As a time trial world champion, however, Evenepoel also hunkers down on his bike like no other. He benefits from the fact that his physique lends itself to an extremely aerodynamic position. This is particularly noticeable on a time trial bike, but he also looks very compact on a road bike, achieving a small frontal area and a compact silhouette relative to his power output. His power-to-cwA ratio is likely to be exceptionally good.

Number of the day: 4:34 minutes

For the tenth stage, we are simulating a breakaway by a 70 kg rider over 125 kilometres. Once again, the fastest bike on this mountainous route is the Cervelo S5, which saves 4 minutes and 34 seconds compared with the R5 model, which is not aerodynamically optimised.

However, our calculations show that weight also plays a part in the result. The Van Rysel RCR-F Pro’s superb aerodynamics do not make a difference on the mountainous route; the bike drops a few places in the rankings due to its greater weight.

An overview of the (almost) full line-up*:

​The table shows the ride times for a 125-kilometre ride. At the top of the list are bikes that combine minimal weight with good aerodynamics.

The “Aero-Power” figure shown is the power measured by TOUR in the wind tunnel to overcome the aerodynamic drag of the bike and a dummy with moving legs at 45 km/h. For the simulation, we mathematically add the rider’s upper body and scale the drag to the actual race speed.

​* Simulation calculations

Based on our own wind tunnel tests, we carry out simulation calculations for the Tour de France tech briefing. How TOUR tests: Aero road bike test in the wind tunnel.

We are investigating which wheels can offer a technical advantage in which situations. The variables we can influence in the simulation include wheel weight, rider weight, the inertia of the wheels, the drag coefficient, the rolling resistance coefficient and the efficiency of the drivetrain.

To model ride times, we use realistic power outputs and weights for the riders, combine these with our wind tunnel data, and have the riders race virtually along selected sections of the route, which we extract from the official route data; the derived elevation profiles are key to this. The modelling also includes bends, which we can brake for realistically, and adjustable power profiles for different types of riders. This allows us to distinguish between attacks on climbs and proper final sprints. Taken together, this makes the simulation highly realistic. What we cannot replicate, however, are dynamic driving effects such as the individual behaviour of the wheels on different road surfaces.

The journey times calculated for the sections of the route that are decisive for the race highlight the influence of the wheels – provided that the riders always behave in the same way in a given scenario.