snorri
Legendary Member
- Location
- East coast, up a bit.
In handlebar discussions, much is made of the advantage of being able to use the drops in a head wind, but no one mentions the disadvantage of drop 'bars in a tail wind even when on the hoods.
How much does wind slow a bike?
- Thread starter davidphilips
- Start date
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snorri
Legendary Member
- Location
- East coast, up a bit.
I didn't read every word on that link, but I think they failed to mention the angle of the cyclists shoulders in relation to the wind, any sailor would know this is critical.
Angling the right shoulder forward in a wind blowing from left to right will have a slowing effect, whereas angling the left shoulder forward will have a beneficial effect.
matticus
Guru
Don't you just ride no-hands? With your arms spread, praising the wonderous weather gods!In handlebar discussions, much is made of the advantage of being able to use the drops in a head wind, but no one mentions the disadvantage of drop 'bars in a tail wind even when on the hoods.
- Location
- Inside my skull
I didn't read every word on that link, but I think they failed to mention the angle of the cyclists shoulders in relation to the wind, any sailor would know this is critical.
Angling the right shoulder forward in a wind blowing from left to right will have a slowing effect, whereas angling the left shoulder forward will have a beneficial effect.
Until you ride off the road into a ditch 😂
- Location
- Inside my skull
If you want to answer the question. Go to the fens on a typical day and ride north. Then turn round and come back south. You’ll soon see what effect the wind is having.
Fab Foodie
hanging-on in quiet desperation ...
- Location
- Kirton, Devon.
...and if you hear Banjos, pedal like buggery....
nickyboy
Norven Mankey
- Location
- You want hills? We got hills
So, to complete the analysis, the average watts required to do out and back ride on a windy day is greater than the average watts needed on a still day, assuming both rides are completed in the same time. Viz; average speeds reduce on windy days. It's all about that "squared" effect of speed on wind resistanceAir resistance is a force so is quantified in Newtons. Multiplying this by the distance travelled (metres) gives energy expended (Joules) and dividing this by time (seconds) gives power (Watts).
This link explains more about how drag force itself is calculated
snorri
Legendary Member
- Location
- East coast, up a bit.
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lol - so have I, although 20yrs later probably couldn't find my arse with both hands regarding most of the subject matter now... that's why i found multiplying force x time a bit unusual.
force x distance sits more easily with me!
(disclosure: i have a degree in this sort of stuff, even though it's not as fancy as some here have
Isn't force x time the formula for "impulse"? My understanding of mechanics gets sketchy once past the basics..
FWIW I'd say that the in real-work terms you'd probably expend more energy / require more power to complete the same ride in windy conditions, but more because of tertiary issues rather than the square drag law - which shouldn't make any difference as that relationship applies whether the wind is assisting or hampering you.
Where the effect of the drag law does become relevant is on hilly terrain since due to the high speeds (and associated exponentially growing drag) encountered on descents, proportionally less of the potential energy gained on the climb is translated back into speed on the descent, if you see what I mean. So, if seeking to maintain a high average speed throughout a hilly ride the best tactic is to expend as much energy as possible attacking the hardest ascents (where speeds and hence aero drag are lowest) and putting in zero energy on the descents while seeking to minimise your drag / frontal area.
matticus
Guru
Oh yeah, I'd forgotten that!
But i think that is most relevant to a body being accelerated; it tells you the amount of momentum gain (from which you can calculate the change in speed, if you know the body's mass). So I think I prefer power and energy for our cycling analysis
DCBassman
Guru
- Location
- The lumpy far South West
Wind doesn't slow up or speed up a bike much at all. The lump on top, that's a whole 'nother thang...
HLaB
Marie Attoinette Fan
This is another site for guaging the impact of the wind AFAIK it only gives a difficulty rating so you have to compare it to your hitstory. I.E. today which felt hard was only a difficulty of 2.1, and tomorrow is only going to be a difficulty level of 0.9, so in theory the wind will have less impact. There's no precise figure though. 
https://headwind.app/
https://headwind.app/
Same result from cycling uphill against a lighter faster rider. The amount of time lost cannot be recovered by being faster downhill, coz going downhill is much shorter in duration.
I don't know many hills where its a short climb followed by a stupendous long descent on the other side.
I don't know many hills where its a short climb followed by a stupendous long descent on the other side.
Ian H
Ancient randonneur
I seem to recall that wind-resistance increases exponentially. This means (I think) that the greater your usual speed the more a headwind will affect it.
More gears & better rolling tyres? Not going to make a huge difference. Weight? might make a slight difference uphill. "Aero" (that trendy term) bikes? See below.
More gears & better rolling tyres? Not going to make a huge difference. Weight? might make a slight difference uphill. "Aero" (that trendy term) bikes? See below.
Wind doesn't slow up or speed up a bike much at all. The lump on top, that's a whole 'nother thang...
JohnHughes307
Über Member
- Location
- Potters Bar
What is this "tail" wind you speak of? My normal route is four sides of a square and I swear the wind is in my face the whole way round 🌬️
