Tour Tech: How bike change strategy shaped the stage 17 time trial

Some riders go on feel, others on data, and equipment decisions play a big part in Wednesday's hilly TT at the Tour de France

EMBRUN, France (VN) — On the results sheet, Chris Froome bested Alberto Contador by nine seconds on Wednesday in Chorges. Behind those nine ticks of the clock in the stage 17 time trial at the Tour de France were a series of decisions and equipment choices that likely went a long way to helping Froome close nearly a half-minute gap in the race’s final kilometers.

The range of equipment selections and strategies for Wednesday’s difficult, hilly time trial was as varied as the riders themselves, with no two taking precisely the same tack. Even riders on the same team, or with the same sponsor, ended up tackling the time trial from different angles.

Alberto Contador (Saxo-Tinkoff) stayed on the same bike for the entire time trial, a Specialized Venge aero road frame with drop bars, aero extensions, and a rear disc wheel. He finished second. His teammate, Roman Kreuziger, swapped the disc for a Zipp 404, and finished fourth.

Chris Froome (Sky) rode his Pinarello Dogma 65.1road frame with superlight wheels, drop bars, aero extensions, and a modified saddle position until near the top of the second of two Cat. 2 climbs, where he threw a leg over his Bolide time trial bike. He won the stage, taking another 10 seconds out of Contador on the GC.

There was no universally perfect setup, applicable to every rider.

“We made the decision not to change to a TT bike. Instead, we rode with a disk wheel,” Contador said after the stage. “It was the right decision for me. I am content with the TT today.”

Froome made a different decision. Following a final recon of the course on Wednesday morning, he and his Sky staff made the call to swap bikes near the top of the second climb. “We thought that the final part of the course was better-suited for the TT bike. I think it made the winning difference because I was still behind Alberto at the second time check,” he said.

At the final check, 20 kilometers into the 32km race, and just after his 15-second bike change, Froome was 11 seconds down on Contador. He finished 10 seconds faster, making up 21 seconds on the final descent. His gamble paid off.

But there is the potential for both risk and reward in any equipment or strategy choice. Bike changes take time, anywhere from 10-20 seconds between the change itself and the loss of momentum, and the advantages of a particular equipment choice can only be roughly calculated.

But calculated they were, and most teams decided that the time lost could be made up. The improvement in both bike and body aerodynamics, and the larger gear provided by a time trial bike, could erase the deficit. Teams like Omega Pharma-Quick Step and Sky were relying on math, not instinct.

Wednesday’s dynamic course, featuring two tough climbs paired with one difficult, twisty descent and one fast descent to the finish, ended up lending itself to the bike swaps that many top riders performed.

“There’s two sides: the stuff that we can model with math —weight, aero, and rolling resistance — and the stuff we can’t model — technical handling ability mostly,” explained Chris Yu, an aerodynamicist with Specialized who helped develop the equipment strategies for Contador and Omega Pharma’s TT world champion Tony Martin.

“In this case, with the two climbs, weight was a the driving factor and most TT bikes build up heavier than the UCI minimum, so that drove the road bike decision. That was compounded with the fact that team recon showed the intermediate descent to be super technical, again favoring the road bike,” Yu said.

It was the nature of the final descent that tipped riders towards the bike swaps. “The last descent to the finish was just a straight comparison of aero drag gain between the TT bike and road bike — in this case extra weight on the TT bike actually helps versus the time it would take to swap. Our mechanics were estimating between 10-15 seconds (for the swap) and the rough calcs I did showed in the neighborhood of 30 seconds gain going from road to TT bike.”

Interestingly, Martin chose to swap bikes before the final descent. He didn’t end up factoring in the stage result, but, if we trust the math, Contador’s decision to stick with his Venge may have cost him his first stage win of the 100th Tour.