Riding in the peloton is no drag

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jserraglio
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Riding in the peloton is no drag

Post by jserraglio » Sun Jul 29, 2018 9:02 pm

WSJ — Sports
A study has, for the first time, established just how much riding in a bunch reduces drag
Every day at the Tour de France is like cycling through a postcard, from the beaches of the Atlantic Coast to the mountain passes of the Alps and Pyrenees.
But for most of the riders most of the time, the view is the same: a mess of bikes, brightly-colored jerseys and exhausted skinny men. That’s because they spend the majority of the 80-plus racing hours from the start of the Tour to the Champs-Elysées tucked inside the peloton, the main bunch that coagulates in every stage and moves like a school of fish.
The peloton exists by practical necessity. Riding in a big group reduces drag and saves energy for the people in the middle. Cyclists have known this for a century. But only now, in 2018, is anyone able to put a number on just how efficient it is.
As it turns out, riding in a tight peloton makes life easier than anyone thought.
According to a new study published in the Journal of Wind Engineering and Industrial Aerodynamics, riders in the belly of a peloton are exposed to 95% less drag than they would experience riding alone. Which explains the sensation all riders describe of being sucked along by the bunch while barely having to pedal.
This is critical to understanding the dynamics of a pro race. Because every ounce of energy saved in the peloton can then be recycled in decisive climbs, sprints and attacks.
“The wind and how it affects you is everything about the sport,” Team EF Education First sports director Charly Wegelius said at the Tour. “But if you haven’t ridden the bike at a certain speed in a group, it’s always going to be hard to understand cycling.”
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The Study
Professor Bert Blocken has ridden into the headwinds of the Low Countries his whole life. So as a keen cyclist who teaches civil engineering at the Eindhoven University of Technology in the Netherlands and the University of Leuven in Belgium, he became obsessed with modeling efficiencies in the sport.
Blocken and his team, backed by both universities and the U.S.-based computing companies Ansys and Cray, decided to simulate two 121-rider pelotons, packed together at different densities.
What they found were that the group of riders in the middle and the back of the peloton were so shielded that they bore less than 10% of the wind. That meant, according to Blocken, that the same effort riding alone would normally have them going a third or a quarter of the speed.
These are, of course, theoretical scenarios that assume the peloton is on a wide, straight road. But Blocken’s findings were already enough to dispel some of the numbers that had been floating around cycling for years. Prior wind-tunnel testing of cyclists in single file had shown that riders in the back experienced 50% to 70% of the drag of the person on the front. Somehow, that became the accepted figure for pelotons too. The issue was that didn’t fit with the anecdotal evidence of pro cyclists who reported far greater benefits.
The study took Blocken’s team a year and a half, in part because of the computing power required. The 121-rider simulation involved a staggering three billion calculation points, Blocken said, in order to reflect every dynamic right down to the 1-millimeter pocket of air that surrounds each rider. The results were confirmed by four separate wind-tunnel tests, including one that featured quarter-scale models of 121 cyclists in race positions.
“We have a problem now,” Blocken said when he finished the study, “because no one is going to believe us.”
The Trade-off
At the Tour, riders and coaches are well aware of Blocken’s study—and they believe it. But they also understand that his simulations are only one piece of the shifting puzzle that is a bike race.
Sitting in the peloton is indisputably the most efficient way to spend a stage. It might also be the most stressful. With riders close enough to rub shoulders they are effectively blind to holes and bumps in the road. They have to pop up to see over the front of the peloton. Any crash or stoppage can turn a momentary mistake into a 30-man pileup.
“There’s a balance,” said Team Sunweb’s Chad Haga. “The guys saving the most energy are also totally trapped. So if it’s an important moment, that’s the worst place to be.”
Races in the Crowd
Just because a rider is cruising along surrounded by 100 other bikes doesn’t mean they can’t play tactics.
A supremely gifted rider like Team Bora-Hansgrohe’s Peter Sagan uses his bike-handling skill to move around the peloton constantly to save energy and stay fresh for his explosive sprint finishes. Because of his preternatural technique and balance, he can keep himself safe in the bunch, and move up and down as he pleases without having to dart outside the peloton and into the wind.
“There’s a lot of things he does that are not textbook,” Mitchelton-Scott sporting director Matt White said. “He’s so unpredictable.”
It also keeps him from getting too comfortable. Do that and you risk getting caught out by the riders pulling the peloton from the front. Their favorite tactic is to vary the pace, slowing the pack as it goes into villages and sprinting out of it them to create a yo-yo effect and force the riders on the back to spend energy to rejoin the bunch.
“I used to do it on purpose when I was pulling,” said Wegelius, who competed in all three Grands Tours as a rider. “Just to mess with them, to make it hurt.”
Peloton. Or Yellow Jersey?
Nothing changes how a team conducts its Tour like holding the yellow jersey. Once your guy is in the overall lead of the race, you quickly discover that other teams no longer want to help you and, suddenly, you’re taking over the responsibility of setting the pace on the front of the peloton.
Which is exactly what has happened to Team Sky, the Tour’s dominant squad dating back to 2012.
The sight of Sky’s platoon of white jerseys with orcas on the back—part of the team’s campaign this season to clean up the oceans—has been a daily staple of this Tour, ever since it took over the lead back in the Alps. The peloton school of fish has become so accustomed to riding behind them that Haga came up with a new name for the exercise: “Whale watching.”
For Sky, it’s a heavy burden. Its support riders, known as domestiques, must be prepared to ride into the wind all day, if necessary. But the team would never dream of dropping its yellow jersey contenders back into the belly of the peloton. Far too risky when your entire season is built around winning the Tour de France.
“If you crash one time there, then it’s not worth it,” Sky domestique Wout Poels said. “So we are burning some riders to keep the leaders in good positions. But on the other hand, we don’t need to be fresh in Paris—just to win the race.”
Write to Joshua Robinson at joshua.robinson@wsj.com
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jbuck919
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Re: Riding in the peloton is no drag

Post by jbuck919 » Mon Jul 30, 2018 11:53 am

My brother-in-law is as expert a cyclist as there is and still at my age (63) rides 20 miles each day to work (he is a high school tech teacher), part of it down a dirt road, every day except in the most severe weather in Vermont. That is only the beginning of the accomplishments I might lay out. He has also been riding a tandem with my sister for decades. I think they still follow the Tour de France, but I also think that his heart was broken when the truth was revealed about Lance Armstrong. You survive a cancer that is nearly unsurvivable, and then you blow it all. Ah well, as Stephen Crane wrote, I think there were stranger tales.

There's nothing remarkable about it. All one has to do is hit the right keys at the right time and the instrument plays itself.
-- Johann Sebastian Bach

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