Toolbox: Time trials are known as the race of truth, and has long been a hotbed for technology and science. Multiply that exponentially when it comes to team time trials, with the need to mesh 4-8 individuals into a sum greater than its parts.
The team time trial (TTT) stage took place this past Sunday in Brussels at Le Tour. There’s the old adage that you can’t win the tour with the TTT, but you can certainly lose it. In the modern era, where oftentimes the final podium is just a minute or two apart, losing even 30 s can put a GC leader seriously on the back foot.
It’s always an incredibly tense stage for teams and riders, even more so than a normal time trial stage. There is no opportunity for domestiques to take the day relatively easy, as every single rider has to fully commit to the cause. It’s also a day of potential intra-team intrigue. I well remember reading Samuel Abt’s stories of the 1984 Tour’s TTT in his classic book “Breakaway”, where he talked about the TTT being an opportunity for teammates to settle scores by putting the massive hurt onto other teammates.
I was a speaker last week at the Science & Cycling conference in Brussels. One of the talks I found fascinating was by Koen Pelgrim from Deceuninck – Quick-Step, all about the TTT testing that they have done. So today’s Toolbox are brief notes and thoughts from this talk:
Lowest Not Always Fastest
Aerodynamics is not always about taking a position to an extreme. This is true for the positioning of aero extensions. Many think that idea is to get the hands and bars as low, flat, and narrow as possible, but this can go too far.
What happens if the bars are too flat? (left) You compensate by sitting up higher. In contrast, by tilting the bars up a little bit (right), your head and back can drop lower. You can also see the helmet tail flows onto the back much more smoothly on the right.
Pelgim showed data suggesting the same trend for the bars being too narrow. It makes it harder to drop your chest low between the extensions, again making you sit farther up. Same idea with the bars being too low.
As the rider makes up the vast majority of the surface area and drag, aero considerations MUST include clothing and equipment. Pelgrim suggests the following wattage savings at 50 km/h:
Speedsuit vs. standard jersey/bibs: up to 20 W.
Aero helmet vs. aero road helmet: 5-10 W.
Shoecovers vs. standard shoe: 5 W.
Optimized gloves vs. standard road gloves: 5 W.
Rubber on the Road
DQS, like many teams, spend time in the wind tunnel testing riders, equipment, and positions. However, Pelgrim sees this as not the be-all and end-all. It’s great for testing, but he feels that it cannot fully replace the variable conditions out on the road.
As a result, DQS conducts both wind tunnel testing along with field testing. They typically do so on a closed car racing circuit like Zolder for safety and laps making it easier for rapid changes and tests.
This is a nice example of field testing not necessarily matching lab or computer testing. The group at Eindhoven University of Technology in the Netherlands has done some wonderful Computational Fluid Dynamics modeling of cycling aerodynamics, and their work suggests that tighter drafting between riders lead to reduced average drag coefficients overall (Blocken et al. 2018). They modelled distances ranging from 0.05 up to 5 m gaps between riders.
However, Pelgrim did not see this trend out in field testing, with gaps of up to 2 m not being a significant impairment in drag. One theory for this is that models and tunnel testing typically have the riders perfectly in line with each other. In contrast, in reality riders ride slightly staggered to give themselves some margin of error from hitting the wheel in front, so this is a dirtier air situation where the gains are not as significant from tight drafting.
Another area where lab and field testing may differ. Modeling suggests that big and small riders should alternate to optimize overall team drag.
In the real world, Pelgim argues that aerodynamics plays a distant second to strength considerations in rider order. As the second hardest position is second wheel, a GC rider (generally smaller and less absolute power) should avoid being placed behind the strongest rider. That’s because the strongest – and often biggest – riders are also taking the longest turns, meaning the GC rider is actually working harder for longer.
In an ideal world, this talk would’ve been a week earlier so that you can see the ideas in action during the Tour TTT itself. Regardless, I think a major takeaway is that there remains a place for actual field testing, rather than relying solely on marketing or lab data.
With the prevalence of power meters, the easy DIY method is to ride at set test speeds and see the average power required. The alternate method is to ride to a set power and see what speed or time is.
Ride fast and have fun!
Blocken B, Toparlar Y, van Druenen T, Andrianne T (2018) Aerodynamic drag in cycling team time trials. J Wind Eng Ind Aerodyn 182:128–145. doi: 10.1016/j.jweia.2018.09.015
Stephen Cheung is a Professor at Brock University, and has published over 110 scientific articles and book chapters dealing with the effects of thermal and hypoxic stress on human physiology and performance. Stephen’s new book “Cycling Science” with Dr. Mikel Zabala from the Movistar Pro Cycling Team has just hit the bookshelves this summer, following up Cutting-Edge Cycling written with Hunter Allen.
Stephen can be reached for comments at [email protected] .