A steep climb on the route: Which bikes are leading the way on the Plateau de Solaison?

Stage 15 is one that everyone hoping to be in contention in the general classification has marked out in bold. A total of 3,950 metres of climbing lies ahead.

Things get tough from kilometre 131, when the Col de la Croisette lies ahead (4.7 km at 11.2%). But the toughest challenge comes at the end. The climb to the Plateau de Solaison is steep and long. Right from the start, it climbs steeply towards the sky with an average gradient of over ten per cent over the first four kilometres; in total, there are 11.3 kilometres to climb at an average gradient of 9.2 per cent.

Double-digit gradients are a real challenge for riders who aren’t natural climbers.

​There’s no doubt that breakaway groups will try to get away on this stage too. But the battle for the general classification is likely to be particularly exciting. Who will stay in the top five, who will move up, and who will have to drop out?

​Today’s simulation takes a closer look at the final climb. Who has the best bike for this steep ascent?

Number of the day: 37 seconds

​In the calculations, the bikes with the lowest weight stand out. Even the Cervélo R5, which is often criticised, moves up into mid-table. At the bottom of the table is an aero bike that is 1.5 kilos overweight; the gap to the top is 37 seconds.

These days, overloaded aero bikes are only for the support riders who set the pace for the first two-thirds of the race. In the final stretch, weight is what counts. The teams will therefore break out their climbing bikes, if they’ve got any, or tighten a few more titanium bolts.

Jonas Vingegaard can sit back and relax. His bike is back at the top of the rankings. The Dane’s only drawback is that his single-chainring setup has larger gear gaps than the standard double-chainring combination. As there are some very steep sections on the final climb, the single-chainring setup may be pushed to its limits there.

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

​The table shows the calculated ride times for the final climb – based on 6.7 W/kg (rider weight 66 kg). The official pace chart lists this riding time, so it assumes a blistering pace! As expected, the bikes with the lowest weight are bunched up at the front. It’s clear: on a gradient this steep, the bikes should be as free of excess weight as possible.

The ‘Aero-Power’ figure shown is the power measured by TOUR in the wind tunnel as required 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 control 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 hill climbs and proper final sprints. Taken together, this makes the simulation very realistic. What we cannot replicate are dynamic handling effects such as the individual behaviour of the wheels on different 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.