spinconn

Watching the Tour, I am trying to learn and understand a little more about racing. I have read that the benefit of drafting increases as you get farther back in the peleton, but only up to a point. What I have not been able to find is what happens after that point. Does the benefit stay level, e.g., after the 7th position (or 8th, or whatever it is) does the benefit stay the same, or does it decrease so that there is a position that is too far back?

eduskator

Jostling for the Best Position in a Peloton - Digital Engineering 24/7 (digitalengineering247.com)

79pmooney

The effect of drafting increases as you move back in the peloton - at uniform speeds as the riders create a mass of air moving with the peloton. But, if the speed is uneven, accelerations tend to string the peloton out toward single file, that cloud effect vanishes and long after the leaders have sat up and are now resting, those at the back are still powering away at full throttle to bring the strung out line back to a peloton.

msu2001la

The problem with riding in the back of the group is that while the draft may be slightly better, the "accordion effect" is worse. Tiny changes in speed at the front get magnified as they ripple through the group, so the speed at the rear can be very inconsistent, requiring constant braking and accelerating to stay in a tight group. The rear is the worst place to be if you're struggling, because those constant little accelerations start to add up and pretty soon you're yo-yo'ing off the back and gaps start to open up.

Pro riders are also aware that the chances of being involved in a crash are significantly higher at the rear. This is part of why top teams with high placed overall riders work so hard to stay on the front.

Iride01 

PM's (power meters) for bicycles are getting less expensive. If you ever decide to get one, then you'll see first hand how much energy you save when you ride behind another. Even just one person in front of you is quite a bit of savings. Depending on the wind speed and direction you are riding to it, you might see more than a 30% savings of energy behind that one person based on my little experience since I got a PM a few years ago.

But as for your thinking that further back is better, it's very diminishing returns soon after that third person if you are in a single file pace line.

Zaskar

So, no. The effect isn't a bell curve, i.e., The decrease in resistance doesn't peak at 4 or 7 or whatever, then reverse. The decrease decreases at a slowly decreasing rate.

But, and it's a big but, like the guys already said, that according thing is real and wipes out any aero advantage. The back of a big peloton can be brutal.

spinconn

Great answers Gents. I shall be a more informed viewer for tomorrow's Stage.

Zaskar

Oh but wait... the guys in the tour are exponentially better at this. As rough as the back of a pro peloton is, we mortals have it worse. Amateurs are much worse at being smooth, anticipating lifts in the pace...

in my first road race (been riding forever), I watch several guys brake so hard they skidded. Two guys went off into the grass/field. These were separate occasions. At one point, I yelled "Guys, relax. It's a Saturday morning group ride. You've done this before." That got a few chuckles, a few "no #$&@. come on guys... " All that from the accordion.

Psimet2001 

The best part about that is that people will slowly realize the comments always come from the guys in the back.

tempocyclist

The image below assumes smooth, constant, and efficient riding in a professional peloton. As pointed out above, in real-life amateur conditions being so far back can be far less efficient than this.

Eric F 

Well...yeah. The guys at the pointy end don't see the bonehead moves happening behind them

genejockey 

I'd love to see the same plot but instead of percentage of solo rider's power, it would be likelihood of crashing.

asgelle

Since you don't provide a reference, I'll assume this is your work. How do you explain the 10% difference in the draft benefit between the second row rider on the left and right?

Eric F 

Just guessing...slight crosswind.

asgelle

Then you would expect the outside rider on one side to always be working harder than the equivalent one on the other side. This is not true. 2nd row right 64%, left 60% would imply wind from the right, but fourth row has right 54%, left 64% (and why is draft increasing decreasing on the left from row 2 to 4?)

Eric F 

I didn't look that close. I expect there's a more detailed explanation that goes with the graphic.

tempocyclist

https://www.sciencedirect.com/scienc...67610518303751

tomato coupe

The model had all the riders with the same foot at the same position -- it creates an asymmetry.

tempocyclist

Just reverse all the numbers... 😂

asgelle

I saw that after looking through the paper. Given the non-linearities, I wonder if his correction of averaging right and left side of the peloton is adequate. My issue with Blocken's work has always been he goes for volume (more riders, more cases, etc.) over depth (accuracy, margin of error, quantification of uncertainty,...). That said the results are probably more than qualitatively accurate.

79pmooney

I'm guessing a slight crosswind as that difference carries all the way back. "Computer, dial up 24 mph, 100 121 riders in classic steady peloton. add 6 mph crosswind from the right. Symmetrical formation, no echelon."