Robot’s Useless Reviews – Aerodynamics

You are the wrong shape. Please don’t take this personally. We all are. Your shoulders are too square, and your pelvis is oriented in entirely the wrong direction. Your head is too big, and your hair, any hair, is a problem. It would be a big improvement, aerodynamically at any rate, if we could get you sidewise to the wind. You’ll want to shave your head too. And oil it.

The thing is, air is abrasive, like sandpaper, but at a much lower grit (confusingly expressed as a higher number). It abrades as it chastens. It’s everything, literally, that’s holding you back. Who would have guessed that the very air you breathe is ruining everything? So we can either remove air or remove parts of you, if we want to go faster.

The funny thing about aerodynamics is that, all things being equal, you do want them (or it?). One reasonably priced way of getting some is this Shimano C46 disc wheel, a 105-level wind cheater available for relatively short cash.

Assuming we are neither going to squish you, like a too round top tube, or file you down, like an offensively functional braze-on, the only answer is to squish your top tubes and file down your braze-ons. When to stop? Ideally, when both are entirely gone. Your braze-on is really much better as a braze-off. Your top tube ought not be a tube at all. Let us work and winnow at the structure of this bicycle which is wholly necessary to the project of cycling and yet wholly inconvenient as a thing of mass and volume.

As physicists love to say though, “None of this is happening in a vacuum.”

For s*&#s and giggles, let’s just state some facts. In the system of rider and bicycle, the lion’s share of the surface area is the rider, hence my opening gambit to this little meditation. Given that the bike is a significantly smaller percentage of the surface area AND that even a round-tubed, standard bicycle is skinny and streamlined in its orientation to the surrounding air, the marginal gain of converting those skinny and streamlined bits to even skinnier and advantageously shapelier bits is extremely marginal indeed. Now reckon with the fact that the marginal, marginal gain we’ve just isolated only really comes into play once we’re traveling faster than 18mph, and one starts to wonder just what we’re playing at.

That’s probably the answer. We’re just playing, two parts suspension of disbelief, and three pinches of ‘it doesn’t matter,’ with a healthy portion of ‘my toy is cooler than your toy.’

It would be cool if we extended this game to the rest of our lives, with the idea that we might gain time on life. Like, I wore a skin suit all day yesterday, so I can sleep 2 minutes and 13 seconds later today. Or, I shaved myself head-to-toe, and so I get to live 1.14 months longer, albeit with a persistent chill.

The trap that aerodynamics lays for us is that it is analog, not digital, which is to say things are more or less aerodynamic. Humans struggle with non-digital information. As a bike builder I know once said, “You know what tube shape turns out to be pretty aerodynamic? Round.” If this quality of air slipperiness was digital, you’d have things that were aerodynamic and others that were aerostatic (the name for gasses that are dense enough not to be in motion relative to their surroundings).

I think we talk about aerodynamics in cycling because of a simple correlation/causation fallacy. The vast majority of us want to have fun on our bicycles, and we equate speed with fun, but the correlation between the two isn’t necessarily a causal one, and the older you get the distinction becomes an even greater difference, which is to say you will never be moving fast enough to have advanced aerodynamics make any difference for you, but you will also understand that speed is only a cipher for what’s good about riding bikes.

For TCI to grow, we need more readers, which means we don’t mind at all if you cut and paste the URL for this piece into an email and send it to all your bike nerd friends. Please do, in fact.

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  1. Jeff vdD says

    Silca’s Josh Poertner says that round is aerodynamically poor

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