A couple of wind questions

palewin said:

The following two questions were prompted by the fact that we've been getting almost daily 15-17mph wind (not counting gusts) here in northern NJ, and I feel like whining about my workouts! First, I understand the concept of "a watt is a watt" but is there any real reason (other than my mind playing tricks) that it feels harder to ride at 250 watts into a 17mph quartering headwind than to ride a 250 watts in more moderate conditions (say 5-10mph wind)?

One thing we get lots of practice with here in NV is wind. It does "feel" harder to ride at the same power, especially if it's gusty. In part it is because it's harder to maintain a constant power because the gusts wreak havoc with pacing. That being said, I've had some of my best workouts (from a physiological perspective) in the wind, especially when I have a headwind on my longer climbs. If it's not so gusty as to be dangerous, I now look forward to riding on windy days.

palewin said:

Second, I played a bit with analyticcycling, and if I did it correctly, their model predicts that 250 watts should result in a speed of about 25mph, while my reality is 250watts and 22mph. (I changed their model slope to 0.00 for flat roads, lowered the weight of rider & bike a bit to account for my 138lbs, and left their default frontal drag number since at 5'8" and pretty normal position on the drops figured that was in range.) Is the obvious conclusion that the difference in power requirements for 25mph vs 22mph is going into fighting the wind? I guess my overall question is whether wind should impact our training zones and intervals in any way.

I find that I have to enter the upper end value for frontal drag to get power/speed numbers that match my training rides (on calm days). That may be in part because my wheels are at the low end of the range aerodynamically and I rarely ride in the drops unless I am practicing TT positions. I think the AC defaults are misleading.

I believe it's mostly psychological, but there are a couple minor differences when riding into the wind: 1) the lower speeds and inertia means that the bike doesn't glide along between pedal strokes the way it does normally, making it feel somewhat like riding up an incline (or riding on some trainers) 2) a gust of wind can quickly decelerate the bike, which requires a power surge to restore the initial speed once the gust passes and makes the power output more variable, 3) unlike hills, the wind gusts can come more quickly and without any visual cues that increased power is needed, 4) in the wind, riders tend to want to shrink into an aero position, which is typically not as efficient in terms of power production.

Other than that, it's all in your head so enough whining -- get back out there and ride! 😄

RapDaddyo said:

If it's not so gusty as to be dangerous, I now look forward to riding on windy days.

Agree. I used to dread fighting the wind when I rode by speed and distance. Now that I ride by power and time, I look for places where it's not as mentally taxing to produce the power. Uphill and upwind I can just sit up and 'relax' while power production stays high. Funny how that works. 🙂

RapDaddyo said:

I find that I have to enter the upper end value for frontal drag to get power/speed numbers that match my training rides (on calm days).

Yep. I use .7 for frontal area, but leave the default Cd at .5. Based on the aero discussion on the recent thread, I'm wondering if .5 isn't too low as well for a rider on the hoods or drops.