Pseudo Scientific Question

AndyF16

Having 'struggled' the 20 miles home yesterday into a roughly 15mph wind blowing acress the Fens, would there be a formula to convert that into the equivalent hill climb in calm conditions?

I presume there'd be a lot of variables like aerodynamics of the bike, width and weight of rider etc, but anyone want to hazard a guess - to me that 20 felt like climbing Ventoux, but that's just me probably :roll:

rick_chasey

Ventoux's probably not the best climb to choose, given that it's the windy mountain and all that...

danowat

I heard from someone on an Audax, that a 20mph headwind was like an 8% gradient, however, I found this on a website.......

at slower speeds, each 5 mph of wind speed equals ~1% of grade i.e. a 20-mph headwind would equal a 4% hill

LangerDan

http://bikecalculator.com/wattsMetric.html

Assuming you (and your bike) were "normal" in terms of weights and size, then for the same effort, you could ride a 4.5% climb at the same speed as you rode on the flat into the wind. (which ties in roughly with what danowat posted above)

Alternatively, you could take the same power and ride more slowly up a steeper hill. 20 kph on the flat into a 27kph headwind would be much the same effort as 10-11 kph up a 10% slope in calm conditions.

careful

Not sure you can make that equation. The gravitational pull of gradients is linear (in proportion with the gradient) whereas wind resistance is the square of speed as far as I can recall. Obviously the aerodynamics of riding position, clothing and the bike might also vary enormously. I know that I am notably rubbish on hills (almost everyone can beat me) but I fare pretty well in headwinds compared to a lot of my mates.

rake

easy, just note the speed you maintained and estimate the equivalent hill that you could climb at that speed. ie the type of wind would slow you down to 7-8mph would be very strong like a steep hill. how long did the 20 miles take you.

Jez mon

careful wrote:

Not sure you can make that equation. The gravitational pull of gradients is linear (in proportion with the gradient) whereas wind resistance is the square of speed as far as I can recall. Obviously the aerodynamics of riding position, clothing and the bike might also vary enormously. I know that I am notably rubbish on hills (almost everyone can beat me) but I fare pretty well in headwinds compared to a lot of my mates.

Do you have more mass than your peers??

You can definitely make some sort of approximation, but it's been a long day at work!

mattshrops

How would anyone know what speed wind they are riding into? do you carry a portable weather station around? as soon as you turn a wheel you create an artificial "headwind" to further complicate matters. so the faster you go the more headwind you create?? does anyone on here seriously think they can guestimate the difference between a 10 or 15 mph headwind anyway. then what about if its at 45 degrees.

Life really is too short to care :roll:

AndyF16

Some great answers, thanks - I would rather think the 20mph is more like an 8% than 4% but never mind eh

If you couldn't be arsed mattshrops, then why not just press 'back' on your browser and find something less insulting to your huge intellect rather than posting that? :idea:

desweller

I think Alex Simmons was involved with a project to fit a pitot tube onto a bicycle.

You could definitely construct a dirty formula for basic estimates, but most aerodynamics relies on empirically derived information anyway so if you wanted something more detailed that you could apply to a wide range of scenarios then you'd have to get into a wind tunnel.