TT pacing - If able to choose: headwind or tailwind first?

Trying to put together a pacing strategy for an upcoming TT challenge, trying to utilize the Goal Average Power (GAP) strategy described by @Coach.Neal.H.

However, as it is not a race where the strategy needs to be adapted to the weather conditions at a set date, rather it needs to be completed within a set calendar window, the opportunity to optimize weather conditions will be present.

So, for a TT course of 21 km going out and back, what would be preferrable; headwind going out or headwind going back? Supplementary information is that the only real uphill section (2.7 km long, at 1.5% average, whereof steepest section 1 km just below 4% average) comes just 1.5 km into the course. Rest of the course is fairly flat. The (ambitious) goal is an average speed of 46+ km/h.

I am thinking that to minimize metabolites accumulation early in the effort, a tailwind going out would be preferrable, to ease the effort going uphill (or just go uphill faster) and then go full gas into the headwind on the way back.

The forecast indicates that both head- and tailwind may be selected on different days, with wind speeds of 2-3 m/s (7-10 km/h). Stronger wind speeds may also be selected (6 m/s tailwind going out), however, I am thinking less wind is better when going out and back.

Any thoughts?

I’m not sure there is a correct answer, though others can correct me shortly…

My personal instinct, usually, would be headwind on the way out because it alleviates the mental game of keeping the power down in the second half. That said, the fact your climb is on the outbound leg would likely make me reverse, make the climb easier with the tail-wind and at least you’re fighting the headwind with the advantage of a (slight) downhill.


Seconded on the headwind first. In my experience, a hill climb will have a dampening on the wind effect anyway, due to a decrease in velocity on the uphill - so less headwind and/or less benefit from tailwind.

I’m thinking you’ll appreciate mother nature’s boost on the return leg!


You can use this model to esyimate the effects:

Thanks @Heretic, I have been playing around a little with it to find GAP, although not with wind and gradient effects.

Still, it feels kind of pointless when not knowing my CdA, and when applying numbers derived from previous rides of the course, the results does not really make any sense.

Example: Last year’s effort I did the 1 km at 4% climb in an average of 36 km/h at 340 w. Applying an average of 36 km/h over the 1 km at 4% with a CdA of 0.25 indicates I would need to push over 580 w for the duration of the climb. Reducing CdA to 0.2 reduces power requirement by 30 w.

Is there something about the model I am not getting?

I’ve usually found the model to be very accurate. My guess is that the actual grade is much less than 4%. Elevation information is quite often pretty error prone which doesn’t matter much when you are climbing a mountain but on what is essentially a flat road it becomes a big factor.

I’m assuming you would remember if you were actually doing 580W so a faulty power meter seems unlikely and the only other way the model could be out by that much is if you were drafting behind a car.

I also played around with the harmonic mean and GAP variability that you linked to and found that riding uphill with the tailwind would be marginally faster. You could also look at and see what works.

I’d think that unless you’re disciplined enough to stick to a power target exactly, the mental aspect of having a tailwind on the return would be more beneficial. If you over cook the outward leg with a tailwind, you’ll die a slow and painful death on the way back!


@Magnito @Alistair_Brown Seconded. And I would listen to this man…



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Haha, I’m quite new into time trialling so I’d be careful who you trust! :joy:

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I did a time trial effort today. Some of us set out a course locally, following the river to keep it flat, a few years ago. We rode it as timed efforts a few years ago. I was just recovering from chemo and very slow.
About two years ago one friend rode it and set a best time, claiming the Strava KOM for the seven people to have ever ridden the route. So I decided to have a go and the same afternoon diverted on my ride home and took over a minute off.
This Thursday the same guy reclaimed the record with almost a minute off my best time so this morning I got up early and had a go before breakfast.
This is the result, two days apart. Pretty well matched.


Interestingly the estimate from with my weight, power etc is correct within 8 seconds so that should reassure you that the calculator had validity.

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Well, I could probably have spent a bit more time learning the calc’s, but have prioritized cycling instead.

Made an effort today, managed to do “only” 45.1 km/h, so did not reach my goal of 46+. Still improved my PR with 1:22 min, which is not too bad though. Will try once more in the coming week.

Realized I should have spent a bit more time in the aero bars outside, and made a few more adjustments, as the position felt a bit different compared to inside on the trainer.

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