dekindy

If what you are saying is true, then at 6'1" and 200 lbs, if I lose 20 pounds I will be slower coasting downhill and slower pedaling into the wind. I agree that I will be slower coasting downhill. But slower riding into a headwind? I don't think so!

bigtea

If you were to ride at 180# against yourself at 200# (remember, all things being equal) in a headwind, over distance you would lose .

Pedaleur

Depends on where the 20lbs. comes from. All fat? Skinny you would win (less wind resistance). Muscle? Big you (more power).

More or less.

rm -rf

If you lose only fat and not muscle, you'll be faster into the wind, since you will have the same power, but a slightly smaller frontal area.

dekindy

Who would lose? I cannot tell what you are saying here.

If I lose weight and retain power, i.e. I lose fat, then at 180 pounds versus 200 pounds, I would have to be faster. I would have a better power to weight ratio and less wind resistance due to a smaller frontal area and probably a more aerodynamic profile.

One of the racers at the training ride said that when he lost 20 pounds his speed went up dramatically. We are riding a very flat course.

ElJamoquio

Yes.

boyze

From another perspective. Assuming the OP and partner's normal riding speed is at a speed where the major resistance is aero drag and they are on a flat, windless course then the majority of the effort is punching through the air. Pretty much a power to drag force balance(surface area and riding form). Add a steady direct head wind and the only thing that has changed is the relative ground speed. The force balance hasn't changed. Hence something else was in play:

- lighter rider overgeared for the wind conditions
- the course was actually rolling
- the wind was gusting
- there was a side component and the ligher rider didn't or couldn't echelon
- heavier rider had a good day

NYJayhawk

Not sure that I totally buy the "inertia doesn't matter on the flats" argument.

In addition to wind, there are other factors that are working against you (friction of your wheels turning, road resistance, etc., etc.). If you assume that all of the friction working against a rider is equal (same wind resistance, and mechanical friction), the rider with more momentum will be overcome these forces more easily.

Of course this assumption overlooks the fact that the heavier rider will need more power to increase his speed (or even maintain it), but you can't just overlook the momentum side of the problem.

This whole thread seems to be delving more into the theoretical side of things that the real-world. For example, it would be virtually impossible to practically test these things near where I live, as there's no such thing as extended flat areas to ride. I know that my size hurts me in climbing where my power to weight ratio can't allow me to compete with equally fit riders who are half my size. At the same time, these same riders are often pedaling like madmen as I coast past them on a run out after a hill...that's pure momentum at work. We're both descending at 40mph, but 50 yards after the hill, I'm coasting at 30, and the little guys are hammering away to keep up.

Momentum will also definintely help a bigger rider fight off a sudden gust of wind.

Momentum isn't the only factor, but it is a factor.

Bobby Lex

ROFLMAO.

Absolutely. If you were in a race against yourself, one of you would certainly lose. But, then again, one of you also would certainly win. Or maybe not. I guess you could end up in a tie.

Could you repeat the question again?



Bob

Duke of Kent

Drag/surface area vs. power (which roughly translates into velocity), the bigger guy will almost always win.

timmhaan

i've always been outridden by larger guys in headwinds. i image it's as frustrating for me and it is for them when we encounter hills.

Pedaleur

For this _special_ case (equal resistance and constant speed), then the force to maintain that speed is the same, so the power is the same. But...

...as you (and others) note, it is a very special case (used to illustrate a point, like most special cases).

"The difference between theory and practice is nothing in theory, and everything in practice."

gregf83 

I lost 25lbs this summer and at 170lbs I am faster into the wind, across the wind, up the hills and down the hills.

umd

The key is "all things being equal". In losing those 25 pounds you likely increased your fitness as well. If somebody went in and liposuctioned out 25 pounds the differences would be less pronounced. You would climb faster but you would probably be slower into the wind and downhills.

gregf83 

The only way you would be slower into the wind is if they made a mistake and suctioned out some of your muscles. Most cyclists who lose 20lbs would maintain or increase their strength while losing the weight hence get faster. I'll grant you that I don't coast downhill quite as fast.

Plow13

see...i am 200 lbs at 6'1...now i have an excuse to this heavy! fore the wind! too bad, i live where its hilly and not too windy =/

StephenH

I'm slow. But I seem to be less slow in a good stiff headwind, so I think it is kind of an equalizer there.

umd

You wouldn't increase your strength if you woke up one day with 20lbs less fat than the day before. You would have the same strength and the only thing different would be your weight. If you had a perfectly steady headwind then the power vs. frontal area would be essentially the same and there would be no change in speed. However, in realistic wind conditions where there are gusts and changes in direction, it would slow the lighter version of yourself more than than the original version. Everything else being equal.

Pedaleur

It depends on if they took the fat from your sides or your gut.

Except...once again...when the gusts cease...

umd

I don't think 20 pounds would make a significant aerodynamic impact regardless of where they took it from.

I've never ridden in wind without some kind of gusting. It's either fairly calm or it's windy with a lot of variability. I've already said that in a steady headwind there would be no change in speed. That would go for no wind as well. In a flat steady-wind condition, the power required to go a certain speed for a similar aerodynamic profile would not be affected by weight. When you start accounting for accelerations of the rider as a result of the wind, then weight starts to come into play.

Voodoo76

A buddy of mine used to get his Tandem out for late season rides now and then. Similar situation, you did not want to attack that thing over the top of a hill or in a stiff breeze Hadn't thought about that in a while till your little ducks comment.

As several others have said Power to Frontal area is king in the wind. (Tandems are a great/extreme example) How aero can you get and stay?

Pedaleur

It was more a joke than anything, but it could very well make a difference. Hard to say. (Of course, just being able to tuck more would help, but that violates our "all else being equal" assumption.)

gregf83 

A decrease in weight will also decrease the rotating mass carried in the legs and require less power. I don't know the distribution of weight on a person but I think if you tried riding with an extra 5 lbs strapped to your legs you would be slower.

Mr. Beanz

Ahhhh! Sooooo that's why all the lil skinny guys challenge me to 10,000 ft climbs but never on the flats into a 40 mph wind!

gregf83 

We're talking about someone who loses excess weight and maintains their strength. Those lil skinny guys would be even slower if they packed on some extra fat.