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Tour de France

Tour de France tech: Inside the TT bike changes that could happen on La Planche des Belles Filles

Should a rider stick with a TT bike when the road gets steep, or transition to a lighter road bike? Like all things cycling, the answer is: It depends.

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Should a rider use a time trial bike on a course with a steep, tough climb, or should he switch to a road bike at the base of the ascent? This question is taking center stage during Saturday’s stage 20 of the Tour de France, which featured an individual time trial to the summit of La Planche des Belles Filles.

It seems clear the choice comes down to a rider’s preference and goals on the stage. But what other considerations go into that decision? How does a rider determine which bike is best for them? Gear matters, but feel matters more.

What’s faster?

Some riders opted to ride their TT bikes all the way to the summit. Photo: Stuart Franklin/Getty Images

Generally, the TT bike will be faster in most conditions, which shouldn’t come as too much of a surprise given the focus on aerodynamics, both in terms of body position and the bike itself. But the stage 20 TT up La Planche des Belles Filles is comprised of 30 kilometers of flat and rolling terrain, followed by a six kilometer climb averaging 9 percent with ramps at the top above 20 percent. That means other factors beyond aerodynamics come into play here.

Notably, TT bikes tend to be much heavier than a typical road race bike. As more and more information becomes available about at what point weight makes more of a difference than aerodynamics, riders now have a tough equipment decision to make.

In our own VeloNews testing,  Lennard Zinn found that a pitch right around 5 percent makes for a tricky equipment choice when it comes to wheels, because at pitches 5 percent and below, deeper aerodynamic wheels present a clear advantage for many riders. At pitches steeper than that, lighter wheels can become an advantage for riders.

So a bike change at the bottom of the steep climb makes sense from an equipment standpoint, assuming a rider’s road bike is significantly lighter than his TT bike. (Pretty much all of them are.) Some riders who likely didn’t want to make a mid-stage bike change ditched water bottles altogether on the TT bike during Stage 20 in a nod to weight reduction. As you can imagine, the relatively flat stage, ending in a steep pitch, presents unique challenges when so much is on the line.

So the answer to the question of what’s faster comes down to the old familiar bicycle racing answer: It depends. Weight matters when the road gets steep, and aerodynamics matter when the road is flatter. The transition itself plays the X-factor.

The transition matters

Other riders like Peter Sagan finished on a road bike. Photo: Stuart Franklin/Getty Images

All of this comes with a major caveat, of course.

In cycling, gains are often measured in milliseconds. When it comes to a bike change, those milliseconds get wiped out almost immediately. It could cost a rider seconds or more, especially if the bike change doesn’t go smoothly. (Victor Campanaerts can speak to that: A botched transition during the 2019 Giro d’Italia ITT effectively ended his stage before the climb even started.) In Saturday’s episode of The VeloNews Podcast, retired rider Jens Voigt noted that riders consider a bike change in an individual time trial to be ‘fast’ if it is 18 seconds or less.

And there are a few factors that govern a bike change as well. Whether or not the team can station a mechanic on the side of the road with a bike, or whether the team must get a bike from a following team car is another factor that can impact the time of the transition.

So the transition from a TT bike to a road bike could indeed benefit a rider based on the terrain and the equipment’s tailored design for it. But even a slightly slow transition could erase all those gains in the blink of an eye. It’s a gamble, no doubt.

Feel matters most

During the Stage 20 time trial, NBC Sports interviewed Neilson Powless (EF Pro Cycling) to get a sense of his decision-making process. Powless noted that he had spent enough time on his TT bike to be comfortable on it, and the idea of transitioning to his road bike mid-stage didn’t seem like a good idea given how much time and effort it would take him to get used to the different position and feel on the fly.

A rider asks a lot of his body during a bike change like this. Since the time trial position is so drastically different than the road bike position, such a transition can be a shock to the system. The change in position requires a transition too: the body needs to adjust. That takes time. It may only be milliseconds, but in cycling, milliseconds count.

Ultimately, riders likely chose equipment based on what they felt most comfortable riding, balanced against the course profile and the rider’s individual strengths — and goals for the TT.

It’s important to note, too,  that a good fit can make or break a rider’s time trial before it even starts. The fastest TT bike isn’t all that fast if the rider’s position isn’t optimized, too. At this point, most, if not all WorldTour teams put riders in the wind tunnel, or have them get professional fits, or both, in order to optimize that position. But some riders just don’t jibe with the TT bike, so a transition to a road bike can prove to be an advantage here — and a likely relief.


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