This is probably a real newb question, but whatever.

I know the benefits of drafting for the draftor, but does drafting make it more difficult for the draftee?

If so, is the increase in difficulty proportional to the decrease in difficulty realized by the draftor?

This is probably a real newb question, but whatever.

I know the benefits of drafting for the draftor, but does drafting make it more difficult for the draftee?

If so, is the increase in difficulty proportional to the decrease in difficulty realized by the draftor?
A trailing rider does not make it harder for the lead rider. There are theoretical arguments that a following rider might lower the drag on the leader, but the magnitude of this effect (if it exists) is predicted to be so small that it is insignificant. No one has published data showing the decrease in drag on the lead rider.

This is probably a real newb question, but whatever.

I know the benefits of drafting for the draftor, but does drafting make it more difficult for the draftee?

If so, is the increase in difficulty proportional to the decrease in difficulty realized by the draftor?

...If he's a back seat driver it could be quite annoying for the draftee! Seriously though under normal circumstances there is no difference. The only example I can think of where it might be possible would be in the case of an extreme tail wind. In that case it would be conceivable that the draftor could actually block the beneficial wind for the dratee especially if the wind were greater than the speed of the paceline. That's just a theory though. Maybe some of the aerospace engineers on this board could shed more light on it as there might be some echolon issues with this as well.

asgelle, that's what I figured, but I always thought that drafting in auto racing did have an adverse effect on the car getting drafted.

Even if that's true, I don't suppose that just because it might be true of auto racing that it applies to bikes.

Speaking of auto racing, the F1 seaosn is almost over. :(

asgelle, that's what I figured, but I always thought that drafting in auto racing did have an adverse effect on the car getting drafted.

Even if that's true, I don't suppose that just because it might be true of auto racing that it applies to bikes.

Speaking of auto racing, the F1 seaosn is almost over. :(
Actually, in NASCAR, the following car does help by lowering the drag on the leader. The speeds and frontal area are much greater than with bicycles though. In F1, the lead car disturbs the airflow over the following one reducing downforce so it's only possible for them to draft on the straights outside the corners and braking zones.

Some studies have shown that the pulling rider does benefit from the close prescence of a rider behind him. But if I remember this right, the benefits were very small - in the neighborhood of 1-2 percent reduction of effort for the rider in front. Apparently, the rider behind smoothes the airflow just a bit behind the leading rider and gives him a slightly better aerodynamic profile. The studies were done with air flowing over the riders directly from their front, so anything other than still air or a dead head wind would negate these numbers.

The reduction of effort for a person drafting closely is said to be around 30% at about 25 mph.

Some studies have shown that the pulling rider does benefit from the close prescence of a rider behind him. But if I remember this right, the benefits were very small - in the neighborhood of 1-2 percent reduction of effort for the rider in front.
I've heard stories like this for some time now, but no one could ever provide hard data. Do you have a source for this?

Actually, in NASCAR, the following car does help by lowering the drag on the leader. The speeds and frontal area are much greater than with bicycles though. In F1, the lead car disturbs the airflow over the following one reducing downforce so it's only possible for them to draft on the straights outside the corners and braking zones.
Yup. Ever seen an F1 car get too close in a braking zone? Less downforce and a -2g deceleration will do nasty things to a race car.

One of my more up-to-date sources is the recent CD-adapco study done on team time trialing. One of the findings (surprising to some) was this:

Quote: Perhaps the most surprising conclusion is that, despite the full force of the oncoming air, the lead rider experiences lower drag than if he were riding an ITT at the same speed. The drag coefficient of the leading TTT rider is 0.277, while that of an individual rider is 0.285. This occurs because the second place rider reduces the influence of the lead rider’s wake, increasing his base pressure and consequently reducing the drag force.

Here's the link to the entire article in Desktop Engineering:

http://www.deskeng.com/Articles/Cover-Story/Taking-the-Drag-Out-of-the-Tour-de-France-20050715558.html

I have two older sources, both in German-language books published in the 1970's. If I can dig out the books, I'll post the applicable texts.

Edit: If you can stand to read the entire article: CFD stands for Computational Fluid Dynamics.

One of my more up-to-date sources is the recent CD-adapco study done on team time trialing. One of the findings (surprising to some) was this:

Quote: Perhaps the most surprising conclusion is that, despite the full force of the oncoming air, the lead rider experiences lower drag than if he were riding an ITT at the same speed. The drag coefficient of the leading TTT rider is 0.277, while that of an individual rider is 0.285. This occurs because the second place rider reduces the influence of the lead rider’s wake, increasing his base pressure and consequently reducing the drag force.
This isn't data. It's the result of a numerical simulation. A simulation of unknown accuracy. The authors don't describe their methods or the models used, e.g., to treat turbulence. They also provide no information about convergence or mesh refinement. Finally, the authors don't include any comparison of any results to actual data. They could easily compare their results to the empirical data for the second, third, and fourth riders in team time trials but they don't . I have to ask why this comparison wasn't included. It seems to me to be the first thing they would do to show that their results were accurate. The fact that they didn't indicates to me either they weren't concerned with the accuracy of their results, or they did the comparison, but the results didn't come out the way they'd have liked.

Based on all this and the existing empirical data that shows no decrease in drag on the lead rider, e.g., Broker et al. (1999) Med. Sci. Sports. Exer., I find these results far from convincing.

[edit]: I see that the authors do include results for the second rider (but not the third or fourth). They show a reduction in drag of 21% for the second rider. Broker at al. measured the reduction at 29.2%. Since the Broker results have been peer reviewed, accepted for publication, and duplicated by other researchers, they can be considered pretty reliable. That puts the simulation results in error by 39%. Since the effect on the lead rider is predicted by the simulations to be less than 3%, the magnitude of the predicted effect is more than 10 times smaller then the numerical error and so is totally unreliable.

Either way any effect is negligible.

This isn't data. It's the result of a numerical simulation. A simulation of unknown accuracy. The authors don't describe their methods or the models used, e.g., to treat turbulence. They also provide no information about convergence or mesh refinement. Finally, the authors don't include any comparison of any results to actual data. They could easily compare their results to the empirical data for the second, third, and fourth riders in team time trials but they don't . I have to ask why this comparison wasn't included. It seems to me to be the first thing they would do to show that their results were accurate. The fact that they didn't indicates to me either they weren't concerned with the accuracy of their results, or they did the comparison, but the results didn't come out the way they'd have liked.

Based on all this and the existing empirical data that shows no decrease in drag on the lead rider, e.g., Broker et al. (1999) Med. Sci. Sports. Exer., I find these results far from convincing.

[edit]: I see that the authors do include results for the second rider (but not the third or fourth). They show a reduction in drag of 21% for the second rider. Broker at al. measured the reduction at 29.2%. Since the Broker results have been peer reviewed, accepted for publication, and duplicated by other researchers, they can be considered pretty reliable. That puts the simulation results in error by 39%. Since the effect on the lead rider is predicted by the simulations to be less than 3%, the magnitude of the predicted effect is more than 10 times smaller then the numerical error and so is totally unreliable.

Does anyone have full text for these sports medicine journals? Abstracts provide no effective information.

This isn't data. It's the result of a numerical simulation. A simulation of unknown accuracy. The authors don't describe their methods or the models used, e.g., to treat turbulence. They also provide no information about convergence or mesh refinement......

You mistook a brief article about a flow simulation study for the actual study. The authors of the brief article could probably help you get a copy of the actual study, which you could review and then comment on at length. Then again, Scotty2Hotty's "either way any effect is negligible" sums the whole thing up perfectly, so perhaps we should just let it rest at that and go ride a bike for a while.

OK, so here's a question then. Why is it an advantage in a team race to have a teammate chase down breakaways and "sit" on a breakaway rider? There would seem to be no advantage to the team captain, or is there?

the other guys in the breakaway either tow the breakaway rider to victory or a high placing, or the break falters, and they all get caught, giving the team leader a chance to attack or for the team to organize a sprint or whatever.
One guy in the break doing no work is hurting the break, thereby helping the team leader in the pack.

OK, so here's a question then. Why is it an advantage in a team race to have a teammate chase down breakaways and "sit" on a breakaway rider? There would seem to be no advantage to the team captain, or is there?

The advantage is that if the breakaway succeeds, the guy who has been sitting on all day will be very likely to win, as the other riders are tired from the effort. Knowing this, the other breakaway riders will be less likely to cooperate with said wheelsucker, and the break will be less likely to succeed. The team captain is happy with either outcome, either he sits in the peloton and the break comes back, or his teammate has a very good chance of winning.

Silas

One guy in the break doing no work is hurting the break, thereby helping the team leader in the pack.
See, this is what I don't get. How is a guy doing no work hurting the break, assuming he's just drafting off another guy and hanging around?

Silas said it well. One guy not working demoralizes the whole break. He's not hurting the break in the sense that he is a drag under the laws of physics. He's hurting the break because he's a drag under the laws of bike riding, or humans, take your pick. He's getting a free ride. He's going to be fresh. He's going to kill everyone when they see the line. Everyone else in the break starts to realize that they're working for him. F that, they say, and the break collapses.

See, this is what I don't get. How is a guy doing no work hurting the break, assuming he's just drafting off another guy and hanging around?

When you draft you can save up to 30% of your energy. Since the wheelsucker/passenger isn't contributing and taking pulls up front for the breakaway group this means when they reach the finish line he's likely to have fresher legs and will beat the rest of the group. No one wants to do all the work just to have a wheelsucker from another team take the win. This serves to demoralize the group and takes the wind out of their sails, making them go slower and thus much more likely to get caught by the main peloton. Wheelsucking is a classic tactic known as "covering a break." If you don't want a break to succeed you try and get one of your guys in there and sit at the end. They'll slow down and that way your team won't have to work as hard trying to chase them back.

Also keep in mind 6 riders working together will beat 5 riders working together everytime (assuming equivalent abilities obviously)

See, this is what I don't get. How is a guy doing no work hurting the break, assuming he's just drafting off another guy and hanging around?

The said wheelsucker can also slow down when it is his turn to pull, which wouldn't help matters much. The others have to realize that he is slowing down, pass him, and then he just grabs a wheel again.