Triathlon - Headwind Bike vs Run

I have an ongoing argument with a co-worker. We are both active milatary and primarily runners, but have both taken up road biking recently as a change. He insists that it is harder to ride into a 15 mph headwind than it is to run into it. I think he is just a better runner than rider and therefore it "feels" harder. I think that aero and mechanical advantage a bike offers has to make riding into a 15 mph wind easier than running into it. You Tri guys seem like the perfect bunch to answer the question...of course it could just be an individual thing I guess.

I have an ongoing argument with a co-worker. We are both active milatary and primarily runners, but have both taken up road biking recently as a change. He insists that it is harder to ride into a 15 mph headwind than it is to run into it. I think he is just a better runner than rider and therefore it "feels" harder. I think that aero and mechanical advantage a bike offers has to make riding into a 15 mph wind easier than running into it. You Tri guys seem like the perfect bunch to answer the question...of course it could just be an individual thing I guess.

I think that the frontal area of a rider down on the aerobars is less than the frontal area of a runner going at the same speed, and so the drag would probably be less. Not having convenient access to a wind tunnel, I have no data for this, though.

How do you define harder?
I know that on a pretty flat road with little or no wind I can ride at about 22mph for a pretty long time. On the same flat road I can run at about 7 1/2mph for a pretty long time also.

Now lets assume there is a 10mph headwind. How much do you think performance will drop off? I would think that on the bike I would drop to about 15 - 16mph (approx. based on experience). I would also guess that my running speed may drop to 6 1/2mph. These are just loose guesses - but approximately based on experience.

If this were the case the drop in speed on the bike would be over 1/3rd while the drop on the run would be about 1/8th.

I think that when biking at 18 or 20 or 22mph wind is so much of what you are fighting against that adding a headwind will slow you down a lot. I think that running 6 - 8mph the main thing you are fighting is gravity and friction. Adding a headwind will make a difference but not as much as on the bike.

I think that when biking at 18 or 20 or 22mph wind is so much of what you are fighting against that adding a headwind will slow you down a lot. I think that running 6 - 8mph the main thing you are fighting is gravity and friction. Adding a headwind will make a difference but not as much as on the bike.
I concur with jennings.

I concur with jennings.

1

Add your speed to the speed of the wind. You can see you are fighting higher total wind speed. Even in the aero position it is hard work.

ya....what they said.....dam people being on here more then me.....;p

thinking back to the days when i studied aerodynamics at college

the resistance you feel due to the air is proportionate to the speed you are travelling at squared.

therefore riding at higher speeds you will be expending much more energy (more drag from the wind in proportion to your rolling resistance) than running at lower speeds (proportionately more rolling resistance or friction with the ground).

so basically

what jennings said :)

guess I owe him a beer

I would much rather run into a headwind than ride into one.