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Discussion Starter · #1 ·
GOOD MORINING RBR!
I live in an area that regularly gets some pretty stiff wind. Today I woke up and the screens on the windows were whistling, which is a bad sign as the wind usually doesn't pick up til the afternoon. The forecast today is for steady 30mph with gusts up to 50.

Naturally, it always blows directly against me on the way home. I'm feeling a little guilty about driving in today. What are your limits for wind? For temperature, I cut off when it's below Freezing ever since I frostbit my esophagus (that was nasty).

on a related note - what's the relation to ground speed and wind speed? It seems to me that a headwind is more like riding uphill than riding fast. I can hold 10-12 mph in (almost) any headwind, but I can't hold the corresponding ground speed <=>wind speed when it's still out.

Festus
 

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I have no problem with temps-I have never been anywhere that it is too cold or hot to ride. If the wind starts to get over 30 we will not add any miles to our commute. Once the winds are sustained over 40 it is time to put our bikes away.

YMMV
 

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Well..

Were Im fromt here isnt much wind, but were at 4500 feet so our winters are 8 months long. I used to commute to a Junior college towards the middle of the county 50miles each way and I remeber days were I would leave at 7 in the morning and pass a temp sign on mainstreet and it was still under 30. Only way I could get any distance training in at the time.
 

· Shirtcocker
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MB1 said:
I have no problem with temps-I have never been anywhere that it is too cold or hot to ride. If the wind starts to get over 30 we will not add any miles to our commute. Once the winds are sustained over 40 it is time to put our bikes away.

YMMV
pretty much the case with me...it's not so much a problem with sustained wind as it is when it's gusting. A 40-50 MPH gust hitting you from the side is bad news. I've been knocked out of my pedals before and I weigh 200. The biggest danger is getting knocked into traffic.
 

· midnight melon mounter
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windy

I've never ditched out on my bike commute because of high wind, but there have been many days when I've wished I had. I ride a fixed to work. If the wind is howling off the lake, as it often is in Spring, the ride home is really bad.

My conundrum is that the wind is always so still early in the morning. By the time it's picked up, the die is cast and I'm riding 18 miles home regardless.
 

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Riding into a wind

festus said:
on a related note - what's the relation to ground speed and wind speed? It seems to me that a headwind is more like riding uphill than riding fast. I can hold 10-12 mph in (almost) any headwind, but I can't hold the corresponding ground speed <=>wind speed when it's still out.
The Force of the wind is related to the square of the apparant wind speed - apparant wind speed is actual forward speed plus the speed of the head wind (e.g. going 10mph into a 20mph produces an apparant wind speed of 30mph).

But the Power to overcome wind drag is related to the actual ground speed.

Va = Vg + Vw

(Va = apparant wind speed, Vg = ground speed, Vw = wind speed)

F = (1/2) x rho x A x Cd x Va^2 =

(Force = rho = density of air, A = frontal area, Cd = drag coefficient)

P = F x Vg

Boiling this all down to equivalent speed at the same power with and without a headwind:

Vs^3 = Vg x ( Vg + Vw )^2 =

(Vs = riding speed in still air)

For example, if you can go 25 mph in still air, you'd go 19 mph into a 10mph headwind, close to 14 mph into a 20 mph headwind, and 10 mph into a 30 mph headwind.

Keep in mind that wind speeds are usually measured at some distance above the ground surface. Actual wind speed decreases as it gets closer to the ground, the so the actual wind at bicycle height is generally lower than reported wind speeds.
 

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The biggest danger is getting knocked into traffic.

...or the converse--getting blown into parked cars. I still can't believe I've never taco'd a front wheel against some curbside barge's bumper while riding during the Santa Ana winds here.
 

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Discussion Starter · #12 ·
Great Answer, Mark!

You must be an engineer or something. I should've been able to figure that out, but didnt' crack a book. thanks.

And Bocephus - you just lay off Alan with those little smiley things. He's a nice guy and don't deserve gettin no complex laid on him right before a long weekend. I totally identify with the situation when the wind kicks up and you're stuck at work. If the die isn't cast then what is? It's either suck up n ride home or be a nancyboy and hitch a ride with a coworker. Great analogy. :thumbsup:

Festus:23:
 

· C 1/5
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Alex-in-Evanston said:
I've never ditched out on my bike commute because of high wind, but there have been many days when I've wished I had. I ride a fixed to work. If the wind is howling off the lake, as it often is in Spring, the ride home is really bad.

My conundrum is that the wind is always so still early in the morning. By the time it's picked up, the die is cast and I'm riding 18 miles home regardless.
I know just how you feel. I check the weather in the morning...its calm, quiet etc, and I see the radar indicating later in the day winds will pick up and I will face a stiff headwind. I know its gonna suck, but I ride it anyway. Any day on the bike is better than one in the car....
 

· Adorable Furry Hombre
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Mark McM said:
The Force of the wind is related to the square of the apparant wind speed - apparant wind speed is actual forward speed plus the speed of the head wind (e.g. going 10mph into a 20mph produces an apparant wind speed of 30mph).

But the Power to overcome wind drag is related to the actual ground speed.

Va = Vg + Vw

(Va = apparant wind speed, Vg = ground speed, Vw = wind speed)

F = (1/2) x rho x A x Cd x Va^2 =

(Force = rho = density of air, A = frontal area, Cd = drag coefficient)

P = F x Vg

Boiling this all down to equivalent speed at the same power with and without a headwind:

Vs^3 = Vg x ( Vg + Vw )^2 =

(Vs = riding speed in still air)

For example, if you can go 25 mph in still air, you'd go 19 mph into a 10mph headwind, close to 14 mph into a 20 mph headwind, and 10 mph into a 30 mph headwind.

Keep in mind that wind speeds are usually measured at some distance above the ground surface. Actual wind speed decreases as it gets closer to the ground, the so the actual wind at bicycle height is generally lower than reported wind speeds.
Pretty close:)--you still need to take into account the direction of the wind, and the rider though, assuming one's headwind is not a pure headwind(IIRC, all those V(x) should be vector quantities)
 

· Shirtcocker
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Room 1201 said:
Pretty close:)--you still need to take into account the direction of the wind, and the rider though (IIRC, all those V(x) should be vector quantities)
geeks...I just use one of these:
 

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festus said:
GOOD MORINING RBR!
I live in an area that regularly gets some pretty stiff wind. Today I woke up and the screens on the windows were whistling, which is a bad sign as the wind usually doesn't pick up til the afternoon. The forecast today is for steady 30mph with gusts up to 50.

Naturally, it always blows directly against me on the way home. I'm feeling a little guilty about driving in today. What are your limits for wind? For temperature, I cut off when it's below Freezing ever since I frostbit my esophagus (that was nasty).

on a related note - what's the relation to ground speed and wind speed? It seems to me that a headwind is more like riding uphill than riding fast. I can hold 10-12 mph in (almost) any headwind, but I can't hold the corresponding ground speed <=>wind speed when it's still out.

Festus
sleep at work?

as noted in the derivation from professor nerdlinger... try to decrease your frontal area. it helps a ton. also decrease Cd by not wearing flapping clothes.

i also have a headwind at times. i try not to use panniers those days, spend the ride in the drops. i also ride very close to trees, etc. on the side of the road. there is a reduced wind near other stationary objects. you have to get very close.

but the best bet... draft a truck! i have been sucked into the draft of a truck and pulled along many times. it's awesome. usually the truck knows i am there.
 

· Endure26
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I live in Kansas. I've gotten into the habit of checking the forecast for wind speed and direction. I've never lived someplace where I needed to do that, but it's a heck of a lot easier riding into the wind for the first part of my ride and then turning with the wind to come home. I've learned that lesson the hard way, getting stuck out with 30miles of headwinds to look forward to after a hard first half. Kinda hard to do if you're stuck with limited options for a commuting route. Today was 25-30mph winds with gusts to ?.
 
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