Tour de France 2024 - Stage 7: Nuits-Saint-Georges - Gevrey-Chambertain | 25.3 kilometres (individual time trial)
The seventh stage is a time trial. The route is not very spectacular. There are 300 metres of elevation gain over 25.3 kilometres. Essentially, there is a gentle climb with a gradient of just under five per cent and a descent - a rolling course that should also suit heavier time trial riders.
The number of the day: 30 seconds
In this relatively flat time trial, aerodynamics are the key to top speed. As we don't have any concrete data on time trial bikes, we ran a bunch of fictitious bikes through our track simulation to show the influence of aerodynamics on riding time.
A five per cent improvement in the cwA value saves around 30 seconds of driving time on the route. At a speed of 52 km/h, a five per cent improvement corresponds to a power saving of around 18 watts (converted to 45 km/h around 12 W). That's a lot. In the wind tunnel, a driver who already starts in a very good position is more likely to achieve smaller gains. However, such improvements are certainly possible when several details are taken together. Because the aero construction sites are numerous:
- Optimum racing suit for the targeted speed
- Customised aero handlebars
- The best helmet for the rider and their body shape
- Aero details: shoes, socks, gloves
- Wheel/tyre combination
- Frame and other attachments
Other ingredients for carefree racing are time trial tyres with optimised rolling resistance and optimised chain lubrication. The time trial bike should also be as light as possible. On the seventh stage, however, the weight effects are small, as our simulation shows. Saving one kilogramme adds 2-3 seconds. If in doubt, it is therefore better to optimise the aerodynamics and compromise on weight.
Simulation of different time trial set-ups for the 25.3 kilometre course*
The table shows the journey times for different configurations, with variations in weight and aero performance. The marked lines with TT9 and TT15 correspond to the five per cent improvement discussed above. For Jonas Vingegaard, who put in a sensational time trial in 2023, we expect cwA values at the lower end of the table. We are excited to see what tricks the riders will pull out of the team trucks here. Keep your eyes peeled! It's all about the details.
Update on the fourth stage: 1x12 aero set-up in the high mountains
Jonas Vingegaard started the fourth stage over the Galibier on a weight-optimised S5 aero racer. He has thus changed his strategy compared to last year, when he often rode the aerodynamically much inferior Cervelo R5.
The Cervelo S5 he rode on the Galibier was special in more ways than one: Vingegaard rode a 1x12 setup and tubular tyres. After analysing the photos, we identified a gear ratio of 52 to 10-36. We have never seen such a set-up in the high mountains.
But as the Galibier is not super steep, this gear was no problem. The longest gear downhill was even bigger than usual and certainly not an obstacle. Uphill we were riding so fast that the smallest uphill gear 52 x 36 was probably not used at all.
The reason for the 1x12 set-up: to save weight and improve aerodynamics. The S5 will probably have come close to the 6.8 kg mark, but unfortunately we were not allowed to weigh it. The aero chainring and the omission of the front derailleur saved a few watts of drag. This made the already very fast S5 even faster. In the wind tunnel, we would probably measure aero values below 200 watts (the benchmark for super aero bikes in the TOUR wind tunnel test with dummy legs) despite the not very deep spare wheels, which Vingegaard probably chose for weight reasons, just like the tubular tyres. Aerodynamically, Vingegaard was better equipped for the descent than Pogacar. Even with the fast Enve wheels, his Colnago is a long way from the aero performance of the S5. One thing is clear: Tadej Pogacar's legs made the difference in the descent from the Galibier.
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.
