The second individual time trial of the tour is quite a bit different from stage 13, as it is the first mountain time trial in the Tour since 2004. Stage 18 starts with a flat 4 km out of Sallanches before turning up the Côte de Domancy, a short but steep climb at 2.5 km with an average grade of almost 10%. From there, riders will continue to climb roads with gradients around 4% towards the Côte de Chozeau, which kicks up to 5.4% for 3.1 km. After cresting the top there is a non technical 2 km descent into the finish in Megève.
| Stage Type | Individual Time Trial |
|---|---|
| Stage Distance | 16.91 km |
| Estimated Time | 00:31:49 |
| Avg. Peloton Speed | 31.88 km/h |
| Avg. Pulling Power | 408.84 watts |
| Avg. Pulling Yaw | 2.57 ° |
Unlike stage 13, there will be no cross winds to contend with on this ITT. Forecasted winds will be low throughout the day and should not provide any riders with an advantage or disadvantage over the others. Temperatures should remain in the low 20s and humidity will hover just about 50% so the conditions should be the same for most riders and not have a significant impact between the early riders and the later GC riders.
This stage represents the best possible place for GC contenders to make time gains on each other. With Froome's performance on Stage 17 it was evident that most GC riders are racing for the 2nd and 3rd positions on the podium. Porte, the only rider that has shown the ability to attack him, has lost too much time early in the race due to his early mechanical issues. This Time Trial sets up very nicely for Froome, Porte and even Dumoulin, who is a bit heavier but has a high enough FTP to compensate. On first glance you would think a traditional road bike would be best suited for a mountain time trial, but on closer inspection the answer is not as simple and very rider dependant. A bike switch does not seem to make sense as you could gain at most 18 seconds using a TT bike over the first 4 km and changing a bike is risky with those slim margins. A select group of riders who have high power and relatively lower body weight like Dumoulin could potentially benefit most from using a pure TT bike for the entire course. Aerodynamics will rule in the first 4 km and the final 2 km of the stage but for many riders these gains would be canceled by the losses in the climbing sections; however, a disciplined rider who is comfortable riding sections under 5% in their aero position could stand to gain time with a TT bike setup. A hybrid setup of an aero road bike with a TT cockpit that allows for some aero positioning at the beginning and end of the course as well as the flatter sections between climbs could provide the best compromise and shave off 10-15 seconds for many riders. With the Time Analysis tool try adjusting power to 0%, weight up 2 kg and CdA down until there is a time gain to find the CdA numbers needed for a hybrid bike to be a benefit.
Analysis was performed by modeling the peloton as a single rider using front of the pack drag characteristics and pulling power targets. Take a look at the entire race plan that was used for this analysis, which includes additional features, metrics and downloadable files.
Stage 18 Race Plan: https://www.bestbikesplit.com/client/44910