# How much does wind slow a bike?



## davidphilips (11 Jun 2020)

Know that cycling into a say 20mph wind will slow down a bike by about 10mph but does cycling in a windy day slow you down much? know it slows me down and i dont seem to be able to maintain any where near a good average speed on any loop? Example on a good day i can cycle one 60 mile loop in just over 3 hours this morning it took me over 3 hours and 40 minutes and i was really pushing as hard as i could (windy this morning) ?
I never seem to be able to gain as much from a tail wind as i loose from a head wind?


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## DSK (11 Jun 2020)

Its certainly been more windy over the last week or so. I can't recall how much it typically slows me down but, as soon as its enough to be noticeable it annoys me and I find myself giving it everything to try and maintain pace, especially with cars on my @ss. I find it easier to make myself more aero rather than try and power through it as the latter is hard work and doesn't really do much.


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## T.M.H.N.E.T (11 Jun 2020)

A tailwind is a phenomenon in these parts, if it's particularly windy I prefer to hide on hillier routes where the wind is generally less of a factor and average speed is going to be lower for that ride anyway.


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## Drago (11 Jun 2020)

I find that wind speeds me up. A diet of beans, duck eggs and Pernod used to shave 5 minutes off my daily commute.


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## davidphilips (11 Jun 2020)

Lol Drago never though of that, what i can not understand if going into a head wind i get more aero yet still can not make up speed/time lost when theres a tail wind?


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## Brads (11 Jun 2020)

I'm struggling with this one as I have spent years bitching about the wind slowing down my average pace.
For reasons unknown to me, I am hitting faster speeds this year even in very windy conditions.
I'm older and have been MTBing all summer only hitting the road bike in the last 2 months but am quicker than before.

Very windy last week and a car driver and his missus clapped and waved as they passed me flying along the flat at near 60k/ph


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## CanucksTraveller (11 Jun 2020)

I am slower in windy conditions, personally I feel it's largely psychological. I kind of feel like it's a battle from the off, and I feel that little bit more defeated (or possibly defeatist) every time I head directly into the wind. I think that just saps my will and mentally knocks me back, translating into less than peak effort and a general "trudge" feel to proceedings. I reckon that feeling of being beaten lasts and hangs like a cloud, even over your "wind assisted" bits. Far from scientific I know, but it makes some sense to me. On a calm day I often fly along with some elation and adrenaline in my veins which I never really feel in the windy conditions.


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## welsh dragon (11 Jun 2020)

I was going to say ask Drago, but he beat me to it.


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## Drago (11 Jun 2020)

Being serious for a moment - which comes difficult for me - I don't think a tail wind speeds me up by the same degree that a head wind slows me down, but it certainly feels a lot blummen easier.


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## nickyboy (11 Jun 2020)

The stronger the wind, the slower your average speed. It's all about the physics.......

Wind resistance is proportionate to the SQUARE of the speed. So imagine you cycle 15 miles out, 15 miles back, at 15 miles an hour on a completely still day. That takes two hours, right? In that time you've suffered 15x15x 2 hours of wind resistance. That's 450 wind resistance units

Now imagine it's a headwind out of 5mph, and you only manage 10mph. That takes 1.5 hours. So to do the whole ride in 2 hours, you need to cycle back at 30mph. Your outbound wind resistance is 15x15x1.5 hours. Your inbound wind resistance is 25x25x0.5 hours. Total is 650 wind resistance units

Of course, you don't manage to deal with the big increase in total wind resistance...so you go slower overall


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## Sharky (11 Jun 2020)

Maths is not my strong point, but I think if you ride for an hour at 20mph with the wind and 10 mph for an hour into the wind, the average would be 15mph.

Unfortunately on the bike, it's not an even time split. You will spend 75% of the time into the wind and only 25% of the time with the wind, so not enough time to make up.


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## Lozz360 (11 Jun 2020)

When it's windy plan your ride so you cycle into the wind on the way out, then you have the tail wind when you return and you're tired. You can also do a loop around a town so that the wind direction means that you are sheltered when riding into the wind and exposed when the wind is behind you.


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## wafter (11 Jun 2020)

Unless travelling extremely slowly air resistance is the dominant factor that controls our speed as cyclists.

Frictional losses, rolling resistance etc generally rise linearly with the change in road speed (so double the speed, double the losses / energy required to overcome them) while aero drag increases with square of the change in road speed (so double the speed, four times the drag / energy required to overcome it).

SImplified (negating the effect of moving wheels, ground effects etc), the influence of wind can be explained with the simple concept of superposition and relative air speed; therefore it takes as much power to maintain 10mph into 10mph headwind as it would to maintain 20mph in still conditions or 30mph with a 10mph tailwind.

In an ideal world a flat loop under wind of constant speed and direction should make no difference to your average speed as the amount of retardation and assistance cancel out.


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## T.M.H.N.E.T (11 Jun 2020)

Then winter happens and everyone is slower again


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## Twilkes (11 Jun 2020)

I once asked a windy question on stack exchange: https://bicycles.stackexchange.com/questions/65234/how-do-sidewinds-affect-forward-speed


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## ColinJ (11 Jun 2020)

Take it to extremes and the facts are obvious!

Let's say that your average riding speed in wind-free conditions is 40 km/hr. If you are trying to ride into a headwind that is so powerful that you can only manage 0.1 km/hr and you ride for 5 hours then you cover just 0.5 km. When you turn round to come back assume that you get instantly transported by the massive tailwind to your starting point. You have covered 1 km in 5 hours, so your average speed is 0.2 km/hr.

The same logic applies to riding up steep hills. Grovel up some monstrous climb for a few hours at a pitifully slow speed and eventually arrive at the top of a cliff above your starting point. Take the quickest route back by leaping off the cliff with your bike. The drop will be a lot shorter than the way up and the fall will take a few seconds, but assume that you fall the same distance as the climb in zero seconds. That makes your average speed twice what you did on the climb. There is no way that you did that climb at 20 km/hr (half your normal speed on the flat)!


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## sleuthey (11 Jun 2020)

davidphilips said:


> I never seem to be able to gain as much from a tail wind as i loose from a head wind?


Same here. I think it’s because when I have a tail wind, if I exploited it fully then it would propel me faster than I felt safe so I tend to free wheel more when I have one


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## Archie_tect (11 Jun 2020)

Unless you live next to railway station and can cycle to the next station with a tailwind and get the train home... observing social distancing.


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## Twilkes (11 Jun 2020)

Sharky said:


> Unfortunately on the bike, it's not an even time split. You will spend 75% of the time into the wind and only 25% of the time with the wind, so not enough time to make up.



That's the correct answer - I can't find the reference but a tailwind helps you more per minute than a headwind hinders you per minute, but you generally spend more time in a headwind for obvious reasons!

The fastest conditions for a circular ride is a still day.


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## Ken Robson (11 Jun 2020)

davidphilips said:


> Know that cycling into a say 20mph wind will slow down a bike by about 10mph but does cycling in a windy day slow you down much? know it slows me down and i dont seem to be able to maintain any where near a good average speed on any loop? Example on a good day i can cycle one 60 mile loop in just over 3 hours this morning it took me over 3 hours and 40 minutes and i was really pushing as hard as i could (windy this morning) ?
> I never seem to be able to gain as much from a tail wind as i loose from a head wind?


Just this minute joined this chat line - with modern bikes and equipment it should not be too much of a problem. Back in the 60's riding a basic "racing bike" we rode to Cambridge (40 odd miles )north up the A10 against a *Very Very* strong gale force wind and *rain* coming in the opposite direction. On top of that we wore the old fashioned capes which in effect made a sail/parachute and possibly did not achieve anything over 5 mph. However coming back we hardly needed to pedal and must have broken a few speed records .


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## matticus (11 Jun 2020)

nickyboy said:


> The stronger the wind, the slower your average speed. It's all about the physics.......
> 
> Wind resistance is proportionate to the SQUARE of the speed. So imagine you cycle 15 miles out, 15 miles back, at 15 miles an hour on a completely still day. That takes two hours, right? In that time you've suffered 15x15x 2 hours of wind resistance. That's 450 wind resistance units
> 
> ...


So does wind resistance have units of Force x time => Newton-Seconds? I'm trying to work out what that means ...

But never mind, I think yours is a pretty good explanation!


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## HLaB (11 Jun 2020)

https://mywindsock.com/ gives an insight but I think it relies on a constant power, which doesn't often happen. Often I'll go out with a reasonable power levels into a head wind and wear my self out and power levels fall significantly therefore I'll not get the full benefit of the tail wind when blown home


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## nickyboy (11 Jun 2020)

matticus said:


> So does wind resistance have units of Force x time => Newton-Seconds? I'm trying to work out what that means ...
> 
> But never mind, I think yours is a pretty good explanation!


The SI of wind resistance is a Grovel. The imperial version is a Pain

Joking aside, that is how the physics works. It's also the explanation for why hilly rides are slower than flat ones, even if you push the same watts for the same time....it's the effect of wind resistance on the fast downhills costing you more than the wind resistance savings on the slow uphills


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## Dwn (12 Jun 2020)

Yesterday, I rode the 18 miles to my daughter's house, and then returned by the same route in the afternoon. The wind speed was (according to Strava) 14.8 mph, and it was pretty steady. On the way out, largely cycling into the wind, I did an average speed of 12 mph, and on the way back it was 14.7mph. Was actually surprised it wasn't a bigger difference tbh.


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## Fab Foodie (12 Jun 2020)

In the minutae, I suspect that a cyclist is probably more aerodynamic to a tailwind than a headwind which means wind assistance is slightly lower than wind resistance.
Crosswinds also play a major role too.


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## dodgy (12 Jun 2020)

There is a decent write up somewhere on the Internet about this. But even if you start and finish from the exact same point and the wind blows (say) 30mph for the entire ride and stays exactly from the same direction, let's say the South, you will always be slower overall than if it was a still day.
You might think the inevitable tail wind will compensate, it does, but not enough.

It's the same reason why pilots carry more fuel on an out and back flight in windy weather.


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## MichaelW2 (12 Jun 2020)

Fab Foodie said:


> In the minutae, I suspect that a cyclist is probably more aerodynamic to a tailwind than a headwind which means wind assistance is slightly lower than wind resistance.
> Crosswinds also play a major role too.


So how can you optimise aerodynamics for a tailwind. Does anyone ride on the tops of the bars or wear flappy parachute jackets to increase air resistance?
My best tailwind experience was on Exmoor. I had to abandon climbing up into a Northerly gale, I was not even going forward. I turned around to ride 27 miles to a railway station. The tailwind boost was incredibly, I cant remember the time but it was fast. My panniers certainly pulled their weight.


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## wafter (12 Jun 2020)

matticus said:


> So does wind resistance have units of Force x time => Newton-Seconds? I'm trying to work out what that means ...
> 
> But never mind, I think yours is a pretty good explanation!


Air 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


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## matticus (12 Jun 2020)

... 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  )


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## Fab Foodie (12 Jun 2020)

MichaelW2 said:


> So how can you optimise aerodynamics for a tailwind. Does anyone ride on the tops of the bars or wear flappy parachute jackets to increase air resistance?
> My best tailwind experience was on Exmoor. I had to abandon climbing up into a Northerly gale, I was not even going forward. I turned around to ride 27 miles to a railway station. The tailwind boost was incredibly, I cant remember the time but it was fast. My panniers certainly pulled their weight.


I tend to sit-up a bit (depending on the wind speed) rather than be bent double over the bars as I would into the wind. I have a spinnaker but rarely deploy it these days....


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## snorri (12 Jun 2020)

Drago said:


> Being serious for a moment - which comes difficult for me - I don't think a tail wind speeds me up by the same degree that a head wind slows me down,


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.


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## snorri (12 Jun 2020)

Twilkes said:


> I once asked a windy question on stack exchange: https://bicycles.stackexchange.com/questions/65234/how-do-sidewinds-affect-forward-speed


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.


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## matticus (12 Jun 2020)

snorri said:


> 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.


Don't you just ride no-hands? With your arms spread, praising the wonderous weather gods!


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## Ming the Merciless (12 Jun 2020)

snorri said:


> 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 😂


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## Ming the Merciless (12 Jun 2020)

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.


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## Fab Foodie (12 Jun 2020)

YukonBoy said:


> 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.


...and if you hear Banjos, pedal like buggery....


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## nickyboy (12 Jun 2020)

wafter said:


> Air 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


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 resistance


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## snorri (12 Jun 2020)

matticus said:


> Don't you just ride no-hands?


Not since my 90th birthday.......medical advice.


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## wafter (12 Jun 2020)

matticus said:


> ... 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  )


lol - so have I, although 20yrs later probably couldn't find my arse with both hands regarding most of the subject matter now 

Isn't force x time the formula for "impulse"? My understanding of mechanics gets sketchy once past the basics..




nickyboy said:


> 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 resistance


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.


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## matticus (12 Jun 2020)

wafter said:


> Isn't force x time the formula for "impulse"? My understanding of mechanics gets sketchy once past the basics..


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


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## DCBassman (12 Jun 2020)

Wind doesn't slow up or speed up a bike much at all. The lump on top, that's a whole 'nother thang...


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## HLaB (12 Jun 2020)

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/


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## CXRAndy (12 Jun 2020)

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.


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## Ian H (12 Jun 2020)

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. 


Ken Robson said:


> ...with modern bikes and equipment it should not be too much of a problem...



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.


DCBassman said:


> Wind doesn't slow up or speed up a bike much at all. The lump on top, that's a whole 'nother thang...


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## JohnHughes307 (12 Jun 2020)

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 🌬️


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## ColinJ (12 Jun 2020)

DCBassman said:


> Wind doesn't slow up or speed up a bike much at all. The lump on top, that's a whole 'nother thang...


I can tell you from personal experience that that may not be true! I'll find my post on the subject...

Here you go:


ColinJ said:


> I was on a Costa Blanca cycling holiday once when the daily ride was cancelled due to dangerously strong winds. I decided to ignore the warnings and went out with a mate. The wind really was nightmarish and we were struggling to ride up to the tunnels leading from Benidorm to above Calpe. As soon as I got to the start of the first tunnel, I hit a wall of wind and was simply unable to ride any further forwards. I was standing on the pedals in a 39/29 gear and using all of my strength but could not move. My legs soon gave way and I was blown off the back of the bike, which took off and headed towards the Armco barrier and the gorge below. I lunged for the bike and managed to pull it back down onto the road ...


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## PaulSB (13 Jun 2020)

CXRAndy said:


> I don't know many hills where its a short climb followed by a stupendous long descent on the other side.



Come to Lancashire we have a few. The ascents aren't necessarily short but the descents are long and lots of fun.

You're overall point is correct one needs a very long descent to regain average lost when ascending. That's generally true on the flat as well, it takes miles of higher speeds to regain lost average.


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## PaulSB (13 Jun 2020)

DCBassman said:


> Wind doesn't slow up or speed up a bike much at all. The lump on top, that's a whole 'nother thang...


Overall I think you're correct. I do know there are circumstances when my speed drops in to a headwind but much of this is how hard one is prepared to work. The biggest motivator is having someone with you.

Three of us road a century on Wednesday, basically in to a 20mph + ENE all day. We maintained an average of 16.4 which we thought good.


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## DCBassman (13 Jun 2020)

ColinJ said:


> I can tell you from personal experience that that may not be true! I'll find my post on the subject...
> 
> Here you go:


I have seen a clip of a cycle race in Cape Town where the riders had to dismount due to being unable to make any progress, then had to hang on to what presumably were very light carbon bikes which were suddenly trying to emulate kites!


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## DaveReading (13 Jun 2020)

PaulSB said:


> You're overall point is correct one needs a very long descent to regain average lost when ascending. That's generally true on the flat as well, it takes miles of higher speeds to regain lost average.



All other things being equal, you will always lose more time on an ascent+descent compared to pedalling the same distance on the flat.


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## gbb (13 Jun 2020)

My take on it was..
I used to regularly do 50 mile loops and generally speaking, whatever the wind was like, I'd generally do it in the same'ish times.
Always head out into the wind, use the drops, that makes quite a big difference and importantly, pace yourself, it's no good fighting the outrun then flagging when you have a tailwind.
In the same way, I always used to attack all my normal weather rides from the start. Then I started taking the first 5 to 10 miles at a slightly steadier pace...and usually found my ride times didnt change, I assume the energy you saved was available later in the ride.
A one off slow time, I wouldnt take any notice of, your fitness on the day can effect that, perhaps just not firing on all cylinders without you even realising it, not fueled well, a lot of unquantifiable things in the mix.


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## BrumJim (13 Jun 2020)

Sharky said:


> Maths is not my strong point, but I think if you ride for an hour at 20mph with the wind and 10 mph for an hour into the wind, the average would be 15mph.
> 
> Unfortunately on the bike, it's not an even time split. You will spend 75% of the time into the wind and only 25% of the time with the wind, so not enough time to make up.



Correct, but more like 2/3 to 1/3. In the example above you ride 20 miles out with the wind behind you and 10 miles back with the wind in your face. So after 2 hours you are still 10 miles and another hour from home.
Therefore average speed will be 40 miles in 3 hrs = 13.3 mph.


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## BrumJim (13 Jun 2020)

JohnHughes307 said:


> 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 🌬


It is. The fastest wind I'm prepared to ride in is around 20 mile/h. Above that it starts to get seriously gusty with danger of tree branches throwing themselves at you. On a still day I can average 20 mile/h on the flat (short ride). With a serious tailwind I can top out at 30 mile/h. Which still gives me a 10 mile/h headwind.


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## ColinJ (13 Jun 2020)

DCBassman said:


> I have seen a clip of a cycle race in Cape Town where the riders had to dismount due to being unable to make any progress, then had to hang on to what presumably were very light carbon bikes which were suddenly trying to emulate kites!


Here's one of a race starting (and rapidly cancelled!) in Benidorm, just a few kms down the coast from where I was blown off my bike! (Not the same year though. They obviously get some serious winds round there!)


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## Ming the Merciless (13 Jun 2020)

This might be of interest, in answer to the question posed.

https://www.yellowjersey.co.uk/the-draft/how-much-difference-does-a-headwind-make-when-cycling/


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## Mike_P (13 Jun 2020)

I find crosswinds worse than headwinds.


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## Twilkes (13 Jun 2020)

MichaelW2 said:


> So how can you optimise aerodynamics for a tailwind. Does anyone ride on the tops of the bars or wear flappy parachute jackets to increase air resistance?



Unless the windspeed is faster than you are riding, which is unlikely for most people in most circumstances, you will still be encountering air resistance from the front, so an aero position would still be fastest.

If the forecast says 30mph winds that is measured some distance up in the air, the windspeed at bike level will always be much lower than that. And people are notoriously bad at estimating the speed of the wind around them, usually greatly overestimating.

So even if there is genuinely a 20mph tailwind behind me, I'm going to be cycling faster than that so will still be encountering air resistance from the front, just nowhere near as much as if I was cycling at the same speed on a still day.

I guess you could ride at 10mph with a 20mph tailwind but why would you? 



gbb said:


> pace yourself, it's no good fighting the outrun then flagging when you have a tailwind.



Thinking back to windy rides and commutes, I don't think I've ever run out of energy with a tailwind, it seems to make things exponentially easier. What I probably do is push the pedals with more force into a tailwind, maybe lowering cadence, and with a tailwind there is a lot less force on the pedals but I'm likely to be spinning faster. No idea why I do this, but spinning 100rpm into a headwind and getting nowhere just doesn't seem to be an option my body wants to accept!


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## HLaB (13 Jun 2020)

gbb said:


> My take on it was..
> I used to regularly do 50 mile loops and generally speaking, whatever the wind was like, I'd generally do it in the same'ish times.
> Always head out into the wind, use the drops, that makes quite a big difference and importantly, pace yourself, it's no good fighting the outrun then flagging when you have a tailwind.
> In the same way, I always used to attack all my normal weather rides from the start. Then I started taking the first 5 to 10 miles at a slightly steadier pace...and usually found my ride times didnt change, I assume the energy you saved was available later in the ride.
> A one off slow time, I wouldnt take any notice of, your fitness on the day can effect that, perhaps just not firing on all cylinders without you even realising it, not fueled well, a lot of unquantifiable things in the mix.


Its that flat round here that sometimes I'll go out into a head wind at a training pace that I know I can't sustain (say 21-22mph), but I'll be blown home still 18mph +. On training rides I don't always bother about the wind direction however and just go flat out on intervals at say 24-30mph with the wind knowing the cool down 5mins after will be a crawl below 14mph into the wind and I'll still get home. Its been an east wind this week and that direction is boring too so I'm ignoring the rule again


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## tommaguzzi (13 Jun 2020)

davidphilips said:


> Example on a good day i can cycle one 60 mile loop in just over 3 hours



Kin' ell 20 mph average! For 3 hours!
You should be doing TTs


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## HLaB (13 Jun 2020)

tommaguzzi said:


> Kin' ell 20 mph average! For 3 hours!
> You should be doing TTs


Depends the terrain they are doing them in. I'll do 21mph in the Fens over that distance (if its not windy), 19-20mph in Northamptonshire, 16-18mph in Rutland and sub 15mph in the Peak District. I do do TT's but I am no where near the top boys, my best on a flat TT is around 25mph, they'll be near 30mph or better


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## tommaguzzi (13 Jun 2020)

Still. 20 mph for 3 hours is some going in a loop where there cannot be wind assistance all the way.
I once tried a one hour tt on British Cycling's closed racing circuit at Middlesbrough.
There was a slight headwind on the very small up gradient on the back straight and quite a few turns which would slow me down. I did 19.8 miles I seem to remember. Just short. I was 10 years younger and a fair bit quicker than I am now and I was tired at the end. No way could I have done another 2 hours at that rate.
While I dont doubt the OP if he can do 20 mph for 3 hours he should think about completing .


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## johnnyb47 (13 Jun 2020)

I find the wind a big factor in my cycling. When I first got back into cycling a few years back i never really noticed it. I would put that down to being a slower cyclist back then and the lower speed = lower wind resistance. Now I'm a little faster i really feel the head winds more. Cycling hard with the wind behind gets some great speeds, but when you turn against it, the resistance of it trying to maintain a quick pace really slows you down. Recently I've slammed the stem on my bike and this has made a considerable difference. Riding on the drops in a head wind really helps battling against it. I would imagine commuter type bikes where you're positioned in a more sit up beg position, you would catch more of that head wind.. I've become quite obsessed in looking for flags on my rides to determine which way the wind is blowing


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## HLaB (13 Jun 2020)

tommaguzzi said:


> Still. 20 mph for 3 hours is some going in a loop where there cannot be wind assistance all the way.
> I once tried a one hour tt on British Cycling's closed racing circuit at Middlesbrough.
> There was a slight headwind on the very small up gradient on the back straight and quite a few turns which would slow me down. I did 19.8 miles I seem to remember. Just short. I was 10 years younger and a fair bit quicker than I am now and I was tired at the end. No way could I have done another 2 hours at that rate.
> While I dont doubt the OP if he can do 20 mph for 3 hours he should think about completing .


If they are doing 20mph in undulating terrain definitely, if its in flatlands they'll still be fast and will have fun competing (I do) but don't expect to compete with the best guys. You'd be surprised what you can do/maintain in flat terrain speed wise


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## SkipdiverJohn (13 Jun 2020)

I reckon the difference in speed for the same physical effort when riding in wind ought to be the square root of the wind speed - assuming you are either directly facing or directly backing the wind direction.


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## MntnMan62 (14 Jun 2020)

Head winds definitely slow me down. The stronger the winds, the more it slows me down.


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## Blue Hills (14 Jun 2020)

YukonBoy said:


> 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.


Shudder. Terrible memories of riding across the fens heading south west fully loaded for a peterborough train.


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## Twilkes (14 Jun 2020)

What is 'a fen'?


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## matticus (14 Jun 2020)

tommaguzzi said:


> ...
> 
> While I dont doubt the OP if he can do 20 mph for 3 hours he should think about completing .


We're now well off-topic, but I'd like to point out that TTs are for everyone (if they can ride 10miles non-stop, anyway!). It's you against the clock, no minimum speed. (bunch racing is a very different thing ... )

And meanwhile, fast people _are_ allowed to ride just for fun!


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## nickyboy (14 Jun 2020)

wafter said:


> lol - so have I, although 20yrs later probably couldn't find my arse with both hands regarding most of the subject matter now
> 
> Isn't force x time the formula for "impulse"? My understanding of mechanics gets sketchy once past the basics..
> 
> ...


You need to do the maths regarding the square drag law. You'll find this is the main reason why average speeds are lower on windy rather than still days. I did a very simple calculation upthread to show why this is the case

Imagine a cyclist who is programmed to produce 150W all the time, regardless of conditions. You'll find his average speed on a windy out and back ride is lower than on a still ride


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## NickWi (14 Jun 2020)

Apologies to Nickyboy but to change his wording just a little. "Imagine a bicycle that is programmed to produce 250W all the time, regardless of conditions."

Buy an ebile, whack it on full power, problem solved!


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## CXRAndy (14 Jun 2020)

tommaguzzi said:


> While I dont doubt the OP if he can do 20 mph for 3 hours he should think about completing



Id never cycled faster than 20mph in a club run. I entered the Tour of Cambridge and at 53 years old averaged 21.3 mph for 80 miles. I wasn't by any means the fastest. Some of my mates average 23-24mph


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## Ming the Merciless (14 Jun 2020)

Indeed on the flat, on my recumbent, I can comfortably maintain 27 mph. If I had a velomobile I’d be comfortably north of 30 mph. I’m no racer, it’s just the aerodynamics significantly reducing the power required.


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## SkipdiverJohn (14 Jun 2020)

YukonBoy said:


> it’s just the aerodynamics significantly reducing the power required.



Predominately aerodynamics, yes, but not entirely. Weight and drag still matter. Last Saturday I did a route on my old Raleigh 3-speed and noted the elapsed time (as it doesn't have a Cateye computer fitted), and yesterday I repeated exactly the same route riding a Raleigh MTB on knobbly tyres with a computer. The distance on the MTB was 19.5 miles and the average speed was 10.7 mph. On the roadster, the elapsed time by stopwatch was a minute less, so the average speed was marginally higher. Both very non-aero, especially the 3-speed. Flat bars set high for comfort. MTB weighs 32 lbs, roadster weighs 41 lbs but even so was still a tiny bit faster. Clearly the knobbly tyre drag not only outweighed the MTB's weight advantage, but also the fact that it was marginally more aerodynamic.


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## Ming the Merciless (14 Jun 2020)

SkipdiverJohn said:


> Predominately aerodynamics, yes, but not entirely. Weight and drag still matter. Last Saturday I did a route on my old Raleigh 3-speed and noted the elapsed time (as it doesn't have a Cateye computer fitted), and yesterday I repeated exactly the same route riding a Raleigh MTB on knobbly tyres with a computer. The distance on the MTB was 19.5 miles and the average speed was 10.7 mph. On the roadster, the elapsed time by stopwatch was a minute less, so the average speed was marginally higher. Both very non-aero, especially the 3-speed. Flat bars set high for comfort. MTB weighs 32 lbs, roadster weighs 41 lbs but even so was still a tiny bit faster. Clearly the knobbly tyre drag not only outweighed the MTB's weight advantage, but also the fact that it was marginally more aerodynamic.



Weight doesn’t matter it’s flat and drag is included within aerodynamics.


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## SkipdiverJohn (14 Jun 2020)

YukonBoy said:


> Weight doesn’t matter it’s flat and drag is included within aerodynamics.



Weight matters as far as acceleration goes, and in urban riding you have to use the brakes more, which turns momentum into heat. So you invest more energy in getting the mass up to speed but can't utilise all of the momentum created because of the need to brake. If weight didn't matter at all, no-one would care if racing bikes were heavy as they would be just as fast as light ones. Frictional drag from tyres and mechanicals is separate from aerodynamic losses.


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## Ming the Merciless (14 Jun 2020)

SkipdiverJohn said:


> Weight matters as far as acceleration goes, and in urban riding you have to use the brakes more, which turns momentum into heat. So you invest more energy in getting the mass up to speed but can't utilise all of the momentum created because of the need to brake. If weight didn't matter at all, no-one would care if racing bikes were heavy as they would be just as fast as light ones. Frictional drag from tyres and mechanicals is separate from aerodynamic losses.



Tyre drag is a not a big factor at 27 mph. Air drag is.

But you are missing the point I’m not maintaining these speeds because of superior tyres to a road bike. In fact the opposite recumbent often have tyres with higher rolling resistance. As to weight recumbents are on average heavier. Yet they still go far far faster than a road bike on the flat. Aerodynamics is king

Velomobiles typically around 20-30kg, three wheels, more tyre drag. Yet leave upright bikes in the dust.


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## Ajax Bay (15 Jun 2020)

YukonBoy said:


> Velomobiles typically around 20-30kg, three wheels, more tyre drag. Yet leave upright bikes in the dust.


Fastest on PBP (on the Plougastel Bridge outside Brest, btw):





(from PBP) when one of these comes past a draft line you hear it behind (and assume it's a quiet car), and then !!!


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