Paceline Aerodynamic Question

skammer

Experts:

are two cyclists faster in a paceline than the lead cyclist alone even if we dont' switch up?...ie. I am in front all the time. Is there an advantage to overall speed/effort for me even if I am cutting the wind the entire ride?

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Lots of Bikes: 1999 Kona Ku, XTR and Race Face. 2007 Specialized TriCross Expert, 2007 Specialized Tarmac Expert Double.

Cannot climb worth a damn, but love to pull my son in his trailer...secret training weapon.

daveryanwyoming

Yes, the rider behind you breaks up the low pressure region behind you much like the duck tail on an aero helmet. Decreasing the low pressure region results in a lower fore-aft pressure differential or IOW less drag. The second rider obviously gets the most benefit from drafting, but both riders benefit to some degree.

-Dave

skammer

OK that is good info...curious because I lopped 2 mins off my usual 7 mile split tonight and thought it was kind of odd. I have dropped 30, 45 seconds off splits before like that but not 2 minutes.

__________________
Lots of Bikes: 1999 Kona Ku, XTR and Race Face. 2007 Specialized TriCross Expert, 2007 Specialized Tarmac Expert Double.

Cannot climb worth a damn, but love to pull my son in his trailer...secret training weapon.

frenchyge

Not sure that's exactly the reason, but I agree that the lead rider could experience a small benefit.

The low-pressure effect results from the flow boundary layer changing from laminar to turbulent as it passes over a body. Whether or not that happens depends on the speed of the body relative to the Reynolds number of the fluid (air) and shape of the body. At cycling speeds it's not a given that there really is a low-pressure suction region behind the lead rider.

However, the trailing rider also directs the airstream away from the trailing edges of the lead rider, effectively smoothing the shape of the leading body, which also reduces the drag somewhat. In any case, the effect is small.

frenchyge

You had a good ride, or good conditions. The benefit of having someone suck your wheel could not amount to 2 minutes over 7 miles.

swampy1970

I know that works with cars at high speed and in theory it should work with anything... Maybe it's time to dig out someone's 24" front wheeled time trial bike from the late 80's!

I surprised that someone didn't invent the team time trial tricycle - two "moser sized" monster disk wheels 18" apart at the back that the rider behind with his 24" front wheel could sneak inbetween!



You could just see the headlines - UFO's spotted in TdF team time trail

bigbadwoulfe

Could it be the adrenalin rush of pulling someone along?

acoggan

That's the theory, but there are some who dispute whether two cyclists are close enough to each other for the effect to be significant. Last summer I (accidentally, really) collected some power data on the indoor track in Los Angeles that suggests that it is, but because these weren't formal experiments I'm hesitant to draw any firm conclusions.

Dietmar

Yes, it is worth noting that the drag reducing effect on the front rider shows a very strong dependence on distance, to the point that the drag on the front rider can, in fact, increase in certain configurations. The only published data I know of are either for generic blunt-body configurations (circular cylinders and such), or for race cars, but they indicate that the distance for effective reduction of drag on the front rider is really close to the minimum (meaning, wheels touching, not really practical...)

In any case, the effect would be of the order of a few percent at best; two minutes off of a 7-mile split cannot be explained by such a small effect.

Spunout

...and probably no effect is seen below 50km/h...