How many MPH do you drop when going against headwind???

[FreshNewbie]

Today I rode in a 18-19mph headwind half of my morning ride. Usually i can hold 18-20mph on a flat but as soon as i face that wind my speed drops to 14-15mph without shifting. I am not fast as it is and to drop speed like that is very dissapointing. Am I out of shape? or it sounds normal? Have nobody to compare to...... Any ideas?

FN

[SnappyPix]

FreshNewbie,

Sounds perfectly normal to me - and if you can maintain 18-19mph on the flat, it doesn't sound like you're out of shape to me!
Typically I can be motoring along at anything from 30-40kph on a nice stretch - but give me a big gusty headwind and this can drop to anything between 20-30kph, depending on the wind speed (sorry, converted to metric when arrived Down Under!).

Headwinds can be pretty demoralising and can totally break a ride - sometimes it's like hitting a wall, cycling through treacle, or at the very worst - pedalling backwards (almost did that once in "Windy Wellington"!!).
Typically I'll try and drop a gear or two, so I'm spinning at a higher cadence - headwinds can be a bit like hills, don't want to mash them!

[salsabike]

The force that acts against you riding into the wind is proportional to the square of the relative wind velocity. If you are going into a 10 mph wind at 10 mph, the force is K*(10+10)^2 = 400 * K. If you are going 20 mph into a 10 mph wind, the force is K * (10+20) ^ 2 = 900 * K

The multiplier K depends on your frontal area and how aerodynamic you and your bike are, and the viscosity of the fluid you are moving through. It's harder to bike through water.

[mimitabby]

hey Salsabike i love your physics

I have been blown by side gusts that almost knocked me down. (scary!)
Wind is terrifically strong and if it slows you down, you're just obeying the laws of physics. Even Lance can't go as fast into a headwind as he can without!!

[Lifesgreat]

Wind is terrifically strong and if it slows you down, you're just obeying the laws of physics.

I guess I ought to obey SOME laws out there. Oh, I will obey the law of gravity too.

[salsabike]

Yeah, headwinds both ways. That always amazes me. I'm always sure I'll get an equivalent tailwind as a reward for bucking the headwind on the way out, and it just doesn't work like that. But no matter how much I know that, I'm always a little disappointed. On the few occasions when it does happen, though---how much fun is THAT??? Screaming back home at 20+ mph. Love it.

[SnappyPix]

The force that acts against you riding into the wind is proportional to the square of the relative wind velocity. If you are going into a 10 mph wind at 10 mph, the force is K*(10+10)^2 = 400 * K. If you are going 20 mph into a 10 mph wind, the force is K * (10+20) ^ 2 = 900 * K

The multiplier K depends on your frontal area and how aerodynamic you and your bike are, and the viscosity of the fluid you are moving through. It's harder to bike through water.

I THOUGHT it must be something like that!!!

All you need to know is that the wind is never with you, it's either against you, no wind at all, or you're just having a really good day!
And even if it's against you, stone me if it doesn't change direction, so it's there again on your way back!

[mimitabby]

And even if it's against you, stone me if it doesn't change direction, so it's there again on your way back!

i thought that was a Seattle weather condition. It happens in New Zealand too?

[caligurl]

FreshNewbie,

Sounds perfectly normal to me - and if you can maintain 18-19mph on the flat, it doesn't sound like you're out of shape to me!

i second that! 18-19mph in a headwind.... you have NOTHING to worry about!

[maillotpois]

I don't drop nearly as much mph as I do when the road goes up.

[caligurl]

the headwind ride that sticks in my mind the most was new year's day this year..... i have this one route that is rolly... but mostly up on the way out.... i was FLYING up the hills... but then.... i had a 25-30 mph (or more... forget now) tail wind! then i turned around..... i was actually using my baby (granny) gear to pedal DOWN the hills! it was AWFUL!!!!!!!!!!!!

i always slow down in a head wind.... and i particularly hate when i have the strong (20-25 mph) headwinds when climbing!!! it's bad enough on a flat... but add it to a hill... UGH!

[Lenusik]

Yes, it slows me down as well, but mostly if I go uphill. I can hold 22-25 pmph on flats without a problem. Depending on the wind strength it can slow me down to 17-20. Going uphill against wind is not fun at all. In places where I hold 14-15 slows me down to 10-12. But if the wind is really nasty - I don't ride at all. I hate those AZ tumbleweeds fying in my face.