How much does wind slow a bike?

[ColinJ]

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:

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 ...

 

[PaulSB]

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.

 

[PaulSB]

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.

 

[DCBassman]

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!

 

[DaveReading]

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.

 

[gbb]

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.

 

[BrumJim]

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.

 

[BrumJim]

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.

 

[ColinJ]

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!)

 

[Ming the Merciless]

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/

 

[Mike_P]

I find crosswinds worse than headwinds.

 

[Twilkes]

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?

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!

 

[HLaB]

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

 

[tommaguzzi]

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

 

[HLaB]

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