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Drafting(18 posts)

Jan 14, 2004 7:44 PM
I was listening to Car Talk on NPR last Saturday, and a question came up about drafting. The caller wanted to know if the draftee (the lead car) experienced any lessened gas-mileage due to the draftor.

Assuming it's pretty much the same principle (bikes vs cars), would the leader experience any type of drag?

FTR, I've never drafted anyone or rode in a paceline - anything like that.
Where's a nascar fan when you need one......TWD
Jan 14, 2004 8:10 PM
I thought I heard something about this a long time ago that in NASCAR type racing the lead car can "feel" the cars behind it. FTR, I've never been to a NASCAR race, and I don't watch those good ole boys on TV (don't own one actaully).

I think the reasoning was that the cars are designed to cut through the wind as efficiently as possible, and part of the equation is how smoothly the air converges behind the car. The less turbulence created behind the car, the more efficient it is slicing through the air. Having another car behind drafting closely messes with the air flow behind the lead car which creates more turbulence, which in turn creates more drag on the lead car.

Not knowing anything about aerodynamics, I'll buy that argument when you're going 180 mph. At 20 mph, I doubt it amounts to anything.

Any negative effect of someone drafting you on a bike is probably in your head. "I know that wheelsucker is going to sprint around me at the next stop ahead sign".

I wouldn't lose any sleep over it.
You get a "push" from behindKerry Irons
Jan 14, 2004 8:47 PM
The following vehicle (bike or car) reduces the turbulence of the air stream disconnecting from the front vehicle. However, the numbers are VERY small at bike speeds, so don't lose any sleep over it. At NASCAR speeds and given the size of cars, it is much more significant.
Yes, A NASCAR Fan Here...Gregory Taylor
Jan 15, 2004 4:20 AM
The lead car in the draft gets a small benefit from the fact that it has essentially grown a long tail, smoothing the air over the roof and off of the rear. On a car running solo, there is turbulance coming off the roof and back end - the presence of a closely following car smooths the air and lessens the turbuance. The benefit isn't as big as being the second or third car in the draft, but it is better than running solo out in the track. You can confirm this by the fact that a pack of middling cars can usually run down even a fast solo car at a big track like Daytona or Talladega. That is, unless that fast solo car is Little E or Mikey Waltrip...
That Mikey guy must win a lot of races nmbigrider
Jan 15, 2004 5:01 AM
Only 3 in his whole career, all on Restrictor Plate Tracks andcdhbrad
Jan 15, 2004 6:01 AM
no, neither he or Dale, Jr. can stay ahead of the draft when running solo.
I was being facetious...Gregory Taylor
Jan 15, 2004 6:38 AM
...but Little E and M. Waltrip do have a good string going at the big restrictor plate tracks.

Not a Waltrip fan? He's not everyone's cup of tea and, no, he's not won a lot, but he absolutely cracks me up when he's interviewed on TV.

Note To Self: be careful when discussing religion, politics, or NASCAR on the Internet.
I was being facetious ME TOObigrider
Jan 15, 2004 7:14 AM
I must admit I have been to two NASACR events and get this, I was in the pits for one race because my brother's best friend was a crew chief for Rick Mast Remington Car. I spent the whole Busch race watching this guy build shocks in the trailer/work van. It was super exciting to me when he explained what he was doing and he used a computer program and specific machine to check each shock.
Point well taken, but drafting on bikes is a blast.cdhbrad
Jan 15, 2004 9:00 AM
I go to Daytona every year and I have to admit the DEI cars do have something figured out at those tracks. They just finished Spring testing at Daytona and the Fords may have something for them this year though. Ricky Rudd, in a Ford was fastest of all.
Rick Mast was one of the nicest guys in Nascar. Too bad he got sick from breathin the fumes all those years and had to end his career early.
Rick Mast traded a cow for his first race carGregory Taylor
Jan 15, 2004 9:10 AM
I used to root for him too... I was really pumped the year that he took the pole at the Brickyard.
You are a FAN, safe drafting (nm)cdhbrad
Jan 15, 2004 9:18 AM
And Safe Drafting To You Too, Sir! (nm)Gregory Taylor
Jan 15, 2004 10:15 AM
Right idea, but backwards...TFerguson
Jan 15, 2004 1:37 PM
There normally is a low pressure area (partial vacuum)behind a car where the air has been displaced and now has to "suck" back in. This also holds the car back. Tubulance weakens the low pressure area (one of the benifits of a rear spoiler) allowing the car to go faster.

A closely drafting car behind now has the vacuum behind him and is using his horsepower to overcome the "suck".

In cycling you get a push from behindbimini
Jan 15, 2004 5:27 AM
It is very significant in a large peleton. A mass of bicycles end on end and side to side creates a big rolling airmass that surrounds the entire group and pushes forward for a short distance in front of the group. I feel the difference between taking my turn at the front and pulling off the front. I believe it is more than just excelleration forces. (I've always got shut down or at best had a few hangers on when I have tried this in races).

By the way riding in the middle of a large Peleton is a real hoot. You feel like your simply cruising and then you look down and see your doing 28-29 MPH. You just have to watch out for the bikes in front of you that are crashing and burning.
I may be wrong but I don't think that is correct...Dwayne Barry
Jan 15, 2004 9:16 AM
at least the part about being "pushed" along by a large peloton. I think once the turbulence is smoothed out behind you, you've gained all the benefit you're going to. I would suspect that this only takes a hand full of riders (and is relatively quite small effect on a bike) not a whole peloton to accomplish. Someone once explained to me that the turbulence behind you creates a low-pressure area and in effect sucks you backwards, by removing that area via smoothing it out with a tailing rider you remove this backwards force. So you in fact are not "pushed" forward but rather "pulled back" less.

Does anybody know is there really a "forward moving airmass" that proceeds the front of a pack or is the first disturbance in the air mass made by the leading riders?
Moving air mass definitely exists.Spoke Wrench
Jan 15, 2004 10:39 AM
I had the opportunity to watch an Olympic development race on a relatively windless day. Each time the peleton went by it generated it's own wind gust that lasted for a few seconds.
Of course, but the question is..Dwayne Barry
Jan 16, 2004 5:56 AM
if you're on the front of the peloton will you physically be pushed by the leading edge of that moving air mass as the above poster contended or is there no benefit to be gained from it until you are embedded in it.
Click and Clack got this one wrong...Cory
Jan 15, 2004 9:19 AM
I heard them talking about that, too, and they got it wrong. I covered NASCAR for several years in the '70s, and while that was pre-computer, they still had it pretty well worked out. The lead car gets a little push if the second car is tucked up close. As I recall, though (it's been a few years) the main benefit comes from the reduction of turbulence behind it. Instead of swirling into a low-pressure eddy that holds the car back, the air flows back over the second car and they both go faster.
Seems pretty obvious that if there were no benefit to the first guy, the pair would be limited to the speed of the lead car. The guy in back would save gas, but he wouldn't pick up any speed, and that's not the case.