TOUR Tech Briefing Stage 11: How much of a difference the bike makes during the attack on the final climb

​From 4 July to 26 July, the world’s best cyclists will be competing in the Tour de France. Victory or 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 11.

Another day for the sprinters? The eleventh stage has a slightly undulating profile, with a total of 1,400 metres of climbing. The final stretch is flat and, in principle, everything is set for a bunch sprint in Nevers. However, the sprinters’ teams’ plans could be seriously disrupted at any time by a really strong breakaway if too few teams contribute to the chase.

The fourth-category mountain climb at the Côte de Billy-Chevannes, 37.9 kilometres from the finish, could be used by strong riders to break up the peloton or a breakaway group and make their move. 1.6 kilometres with an average gradient of 6 per cent isn’t exactly a lot, but it depends on how hard the pace is set.

At least one sprinters’ team is presumably not interested in setting up a classic sprint: Alpecin Premier-Tech. The team has already executed two perfect lead-outs, with Mathieu van der Poel as the final lead-out man. But the team’s sprinter, Jasper Philipsen, was unable to finish the job. This was particularly evident on the eighth stage, where Philipsen was perfectly positioned to launch his sprint. But nothing happened. Philipsen was unable to accelerate visibly, and from the back of the peloton, Tim Merlier shot to victory in commanding fashion, even though his starting position was much worse.

It is therefore unlikely that Alpecin will try the same tactic a third time. Merlier seems to be the stronger contender at the moment, whilst Philipsen appears too weak. It also seems unlikely that they would reshuffle the sprint train with Mathieu van der Poel as the final sprinter, as van der Poel lacks Merlier’s explosive power. As a breakaway rider, however, he is almost certain to succeed. That is why van der Poel might be tempted to attack well before the finish again on the eleventh stage. On his own, though, it is too far; the right combination of riders must come together for a breakaway to work.

A slight incline as a springboard to victory?

In today’s simulation, we’ll be looking at the extent to which the bike aids an attack on the Cote de Billy Chevannes. How fast will a rider go if they attack full out on this climb? What role does the weight of the bike play in acceleration?

Our calculations show that the speed profile on the hill depends heavily on how the approach is managed. In principle, speed is reduced because riders carry momentum from a gentle descent into the climb, which somewhat mitigates the effects of weight.

The maximum climbing speed that can be maintained is around 35 km/h, whilst a peak speed of 40 km/h is possible at the start of the climb. This means that drafting already plays a significant role. Anyone wanting to break away from such a pack must therefore accelerate to create a gap.

As the climb continues, what counts is the combination of good aerodynamics, low weight and outstanding 2.5-minute power output. A 75-kilo rider must maintain 650 watts to reach 35 km/h on this climb.

Number of the day: A 6.5-metre gap for a pure aerodynamic race car

​Analysis of the short climbing section once again highlights the advantages of aerodynamically designed bikes. Cervelo’s S5 is once again the fastest, thanks to its combination of minimum weight and good aerodynamics. In second place is the Tarmac, also at minimum weight but with slightly poorer aerodynamic performance. However, there is only a two-tenths-of-a-second gap between the bikes.

What is more interesting is that the fastest Aerobike, the Van Rysel RCR-F Pro, falls slightly further behind on the hill due to its extra weight. Seven tenths of a second equates to a A gap of 6.5 metres.

The lightweight bike is left well and truly behind, trailing by 2.3 seconds. Overall, the bike’s technical specifications aren’t a major factor in pulling away on the short climb. Pedalling power and tactical decision-making are what determine the outcome.

However, the race won’t be decided on that hill, but further on. Should a scenario like the one outlined become a reality, one thing will once again be paramount: keep your head down and maintain your pace. Aero, aero, aero. The combination of rider and bike aerodynamics determines how quickly the finish line draws nearer.

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

​The table shows the time taken for an attack on the Côte de Billy Chevannes. A top rider puts out around 650 W here and, once the momentum from the approach has been used up, climbs at 35 km/h. Speed is a key aerodynamic factor, but weight also plays a part. That is why the fastest bikes are those that combine good aerodynamics with minimal weight.

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 rider weights, 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 very realistic. What we cannot replicate, however, are dynamic riding 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.