If I know I'm going to be grinding into a headwind for a lengthy period of time, let's say an hour, I find the pace at which I know I can sustain it for that long. Any faster and I'll be worn out and wear down too soon, if slower I'll just be prolonging it longer than necessary. I use the same technic for long (century + ) rides - set the pace at the beginning that I know I'll still be able to hold at the end (granted, I take these long rides as "tours", not "races", so that may not be the fastest way to ride them, but it's how I enjoy doing it.).

Late 1980s - I and other members of the SBC's infamous "Wild Bunch" outlaw racing team headed north out of Shreveport on a Saturday morning training ride. We found ourselves easily piling on the miles and decided to ride to Arkansas - a mere 62 miles away - "just for the heck of it". We made it over the state line and turned around at a closed liquor store/gas station. That's when we noticed the HEAD WIND. Oh yeah, our easy trip north was facilitated by a tail wind that had become our enemy. At some point on our return leg I vowed to KILL my friend David for leading us on this fools errand. David poured it on to stay out of my reach and I relentlessly pursued his Rossin - all the way back to Shreveport. We hugged and made up, then all headed to Don Carlos Mexican Restaurant in Bossier City where mega stacked enchiladas and mucho cerveza were consumed in celebration of our impromptu double metric century.

I know from my years of experience when to back off for the long haul outlook. I'm getting better at it... only 25+years of experience though.

I agree with that. However, I don't see any reason to drop your effort into a headwind (the original post I was responding to) unless you don't care how fast you're going.

Funny this just came up. I am a masher , seldom if ever leaving the big chain ring. Here in Va where I live, there are allot of nice rollers nothing really requiring the small ring. All that said, I HATE WIND...Anyway, I have always just mashed on and suffered. For some reason, about two weeks ago with some 30-35 mile per hour winds, and higher gusts I dropped down to the small ring, grabbed the drops, and pedalled a nice steady 80 rpm cadence...may not be the fastest way to cut through the wind but it felt like heaven to me!!

Wind can be helpful if used to your advantage. Living in a place where wind is the daily staple rather than the occasional thing, I tend to use it to my advantage. I mostly ride solo, so I can vary my rides however I want. As said before, always go out with a head wind and come back with the tail wind. I sometimes do mashing in a hard gear and low RPM and some other times I do spin in an easier gear depending on the length of the ride and the distance I am going to be against the wind. I see rides not as a training session for events (races and such), but rather as work out. I want to get better, so the only way to do that is to put a hard effort. Whatever that is for you. It never ceases to amaze me when I ride with some local people that always ride with other people how quick they are to get off the front.

There is no question the most ideal way to ride into a headwind is behind someone else, but that also limits your speed and effort to the best the guy in front of you can do and for how long he can do it.

Find a climb between you and your destination, and change the route. Sometimes the hill will block some of the wind, and if it doesn't, you're already going slow and hurting so it can't get much worse.

I always thought it would be more efficient to go easy against the wind just for the simple fact that wind resistance increases with the square of your velocity. So I set out to prove my intuition correct using the bike calculator at https://bikecalculator.com/veloUS.html and a few assumptions. Strangely I ended up proving myself wrong. Here are the results:


Assumptions:
Rider weight: 150lbs
Bicycle weight: 22lbs
Position: drops
Tires: clinchers
Grade: 0%
Head wind: 10mph
Course: 20 miles out against the wind, 20 miles back with the wind
Temp.: 75F
Elevation: 100ft
Trans. Efficiency: 95%

Scenario 1: Rider outputs a constant 100 watts the entire race.
Time out: 109.64 minutes
Time back: 53.21 minutes
Total time: 162.85 minutes
Power rate: 1.228 watts/minute

Scenario 2: Rider outputs 110 watts against the wind and 75 watts with the wind.
Time out: 104.14 min
Time back: 58.45 min
Total time: 162.59 min
Power rate: 1.1378 watts/minute

Scenario 3: Rider outputs 90 watts against the wind and 160 watts with the wind.
Time out: 116.17 min
Time back: 45.99 min
Total time: 162.16 minutes
Power rate: 1.54 watts/minute

In all three scenarios the riders finished with the same time. But in scenario 2, the rider used much less energy. So you can see that it's most efficient to go hard against the wind. In scenario 2 the rider went an extra 10 watts against the wind and backed off 25 watts with the wind. The total time was the same as going a constant 100 watts but he used 7.3% less watts/minute.

Power against aero drag is a cube law for ***air speed.*** So making 15 mph into a 15mph wind will take EIGHT times the power output of making 15mph when the wind drops to nothing. For certain wind conditions, Machka can't help but be right. How often these occur is another matter..

Btw - I think you misread what Machka wrote: he didn't say "Save your effort for the return when you'll have a tailwind" but "While riding into the wind, take advantage of brakes in that wind to give the bike the gun."

Empiricism! Good for you!

Big difference between a time trial and a 400k brevet.