Brian Ratliff

Sure is weird that something "as simple as that" is constantly in discussion...

You should ask yourself... is it really as "simple as that"? Or are you just trying to get the last word on an internet discussion (thus far proven to be not possible - if you want the last word, it is impossible to have the last word, on the internet; this is a corollary of Godwin's Law).

Jseis 

It was his attitude. Sure thing on the physics of it all. I actually forgot about him for a while. I could be wrong on this but an effective pace line is a group of cooperating individualists. Irony there in the parasitic mutualism.

Dudelsack 

Your real name must be Pikup Andropov.

You fellers ride fast because yer always rushin' around.

Get it? Har.

It's OK. My youngest daughter is Russian. When I walk around the house she gets right behind me and dares me to drop her.

tagaproject6

Soviet Russia called...you can keep Yakov Smirnoff

Commodus

You're Cat 3 and you've really never been in an accident caused by someone running into you from behind when you had to brake for something unexpectedly?

I have had this experience...but I am only Cat 4 so maybe I don't have your skills. Well actually I did manage to stay up, but I think that was luck rather than skill.

But then, I guess you could make the argument that this could happen no matter the skill level of the guy behind you. In truth, I worry much less about people who draft me than those who actually enter rotation. I don't really want random folks actually in the line.

Brian Ratliff

Physics is physics; don't confuse physics with psychology. An effective paceline is a fast paceline. Sometimes people pull, sometimes they don't, sometimes they can't. If you don't want someone on your wheel, then have a little chat like civilized people. Pull up next to him or her and say: "I'm new at this sport and aren't comfortable with people drafting off me."* I bet they back off.



*It is pretty rare that experienced road riders have a problem with drafters.

Brian Ratliff

I do not make it a habit of braking hard. First, we bike on roads made for cars rolling at 35-65mph; on a bike going at 20mph, there are very few things that happen suddenly enough to warrant hard braking. Second, if you really do need to jam on the brakes, then there is likely already a crash in progress; all bets are off and what happens happens; not much one can do about it - I really don't think about it much.

I watch the guys in the rotation. Even if they are people I know, if they aren't working with the group or riding predictably, I talk with them.

Seattle Forrest

Doesn't sound stupid in the least.

Commodus

Hmm, yea that's definitely a good point...

Our group has to deal with areas of heavy traffic in between our favoured spots, so maybe everyone is just a bit more nervous due to the constant danger of having autos coming from several directions. In that environment, it's quite important that folks keep their distance, as braking is often a necessity. Of course, that's hardly a paceline situation, and the people in the group need to understand that.

Elduderino2412

personally i don't really care if someone drafts off me as long as they announce they are back there. If they don't sometimes they sneak up, and scare the piss out of me.

asgelle

I'll have to remember that the next time I'm cycling at 200 mph (with several square feet of frontal area). For normal cycling speeds, no one has been able to show any reliable data that drag on the lead rider is decreased despite all the field testing that has been done.

Brian Ratliff

No need. The point was the guy felt like the drafter was somehow impeding his progress (describing him as a "poacher"). This is clearly not the case.

And, as the weight weenies will tell you: "if it matters a little, it matters". The physics are clear. That it can't be measured is problem with the measurement tools, not the physics. Nobody is arguing that the effect is large at cycling speeds. (Also, the "sports science" community is laughably low tech and non-rigorous...)

CenturionIM

You don't think it's simple? You draft someone randomly. They say hey man I don't like that. Stop drafting me. And you keep drafting him. Is that not harassment?

And stop putting this nonsense about "having the last word" in my mouth. Also please stop with the physics/internet metaphilosophy stuff. We all know drafting makes everybody faster. People just don't want to be drafted by stranger, simple as that

rangerdavid

In Russia, women are like bus...............





that's it.








.... and **** of course

asgelle

Actually the physics is far from clear. The Reynolds number for a race car is 2-3 orders of magnitude greater than for a bicycle and rider so trying to use that analogy fails. If you look at the pressure distribution on a bicycle, scaling arguments show that to have an effect on the pressure drag, the gap between the lead and following rider would have to be less than a millimeter which is never accomplished in practice. So that only leaves viscous drag as a possible mechanism. Again, scaling arguments show that the separation between riders is too great to have any impact directly on drag. The only conceivable mechanism by which a trailing rider could lower the drag on the leader is then changing the pressure distribution over the front rider so that the point at which the flow separates moves. This is hypothetically possible, but again there is no data which supports this.

However if you want to believe that there is an effect so small that it can't be detected, there is no way to counter that argument since by definition, no proof can ever exist. However it should be noted that field testing has been able to tease out differences of less than 1% so that gives an upper limit to what the impact could be.

rearviewbeer

Drafting off someone while out riding that is not in your group without permission or announcement, makes little sense to me. I ride alone much of the time, drafting would not make the training as effective. When I want to ride with others and draft, I join a group. A 35 mile solo ride can be as effective as a 50+ mile group ride.

In an organized ride, I think differently. We are all there to ride with other people and drafting is to be expected. I had a wheel sucker this past Sunday on an organized ride, I expect it and do not expect people to reciprocate. Were it to bother me, I would drop him or pull over. No big deal...

rearviewbeer

Suprisingly drafting not only helps the bicyclist following the leader, but the lead cyclist gains an advantage as well. Paul explained, "The interesting thing is by filling in her eddy you improve the front person's performance as well. So two people who are drafting can put out less energy than two individuals (who are not drafting) would covering the same distance in the same time." While the lead cyclist gains some advantage in this situation she still needs to expend much more energy than the cyclist who is following.

banerjek

There is a benefit to drafting. But that doesn't mean that people necessarily want to enjoy that benefit for the simple reason that it obligates you to ride differently. Sometimes, I'm happy to work with others. Other times, I'd just as soon not take care of someone on my wheel.

I've never had problems with people drafting when I don't want them to. Like many other people, I use positioning to communicate what I'm up for. It's pretty easy to pass or present yourself to an overtaking cyclist in a way that communicates if you feel like working together. And if people are too clueless to take a hint when you don't, you simply slow way down or kick the pace way up.

aramis

No one I don't know has ever hopped on my wheel while riding. Kind of wish someone would, but I don't ride well traveled roads at well traveled times usually.

I have had people hop on my wheel while riding on informal non-paceline recreational club rides (sneaky people!). A lot of times I don't know for a while, but it doesn't bug me. If I know they are back there I'll ride more predictably though (no surging for hills and such) to be nice and give them some help, so it can be in their interest to announce.

caloso

My dad used to say "just because you can do it, doesn't mean you should do it."

kenji666

When I pass someone, I make them earn the draft, so I drop the hammer and I'm motivated to ride faster. As soon as I hit a hill, I'm gone, and they suffer.

pdedes

When I pass someone, I occasionally offer an invitation to draft. But not always.

Buzzatronic

So why do we ride with water bottles full of oh-so-heavy water that we're not drinking very frequently? Why do I see pro riders with support cars 100' away still riding with multiple bottles attached to their bike, slowing them down? It's adding weight and is not aero for sure. If the theoretical drag benefits of having someone behind you matters, you'd think the guys who's job it is to get every bit of efficiency out of a bike would not carry around a pound or two of extra fluid on their bike. And they ride in packs much larger than one guy sucking my wheel.

Brian Ratliff

I'll buy "less than 1%". Again, no arguments on the magnitude. I am arguing that the trailing rider does not increase the drag on the leading rider. At worst he is benign.

I don't think I buy the scaling argument. Seeing NASCAR races on TV, the cars are rarely outperforming each other by more than a percent, yet it is dramatically obvious when a car falls out of line that it slows dramatically relative to the lead car. This is a different effect than in cycling, where the paceline is faster due to shared effort. In a NASCAR race, the head of the line rarely changes and the throttle is full down a majority of the time. Cars don't get tired; the effect is due solely to aerodynamics. It could be the lead car is a little better than the trailing cars, however this effect seems to happen regardless of who is on the front. The cars trail each other by up to about half a car length. A car length is roughly 5m giving a trailing distance of about 2.5m. Scaling the Re by 40 (10x speed, 4x width, same height) will give us 63mm, or about 6cm (assuming the relationship is more or less linear). More than your "less than a mm". Moreover, the Cd of a bike is about 4x larger than that for a NASCAR race car; I assume more drag/vehicle means the effect is enhanced meaning a scaling might allow 4x the following distance, or 24cm. This puts us in the range of where cyclists draft.

I wouldn't build anything based on these rough scaling laws. The relationship might scale nonlinearly by Re; probably does. Even so, it is far from clear to me that the effect is absent in cyclists, even if the effect is small. If you are privy to windtunnel data (I'm sure this has been done by team pursuit teams; they would probably like to know when it is safe to shed the extra rider), it would be interesting to me to see. A couple things though: 1) the Re difference between a racing cyclist and a race car is something like 25x-40x, not "2-3 orders of magnitude", and 2) your mention of "less than a mm" requires some documentation for me to believe, or at least a mention for the scaling laws used to arrive at that number.

Brian Ratliff

As in cycling as in life: there is a tradeoff between the convenient and the optimal.