Updated: Jul 27, 2021
Considering that it’s the single most important element to going fast on a bike, it’s a bit worrying just how long it took cyclists to start looking seriously at aerodynamics.
In the 1870s, penny-farthing riders quickly discovered that they if they hunched down over the bars, they went faster. Penny-farthing racers transferred this knowledge to chain-driven bikes. But then, for getting on towards 100 years, putting your head down a bit was about as far as it went.
There were only one or two deviations from that norm. In the 1930s, the recumbent bike appeared, and was obviously faster. The faired-in recumbent was faster again. But you weren’t allowed to ride them in official races, and no one really transferred the experience gained to the upright bike. In 1936, Maurice Richard prepared for a successful world hour-record attempt in a Parisian wind-tunnel. Whatever he discovered didn’t stop him riding the record in an entirely conventional position with a flapping jersey.
The obsession for most of the period was weight. Grams were shaved off, one by one if necessary, and despite making relatively little difference to speed other than when climbing a steep hill, the conventional wisdom was that weight was what mattered.
There was an ironic high-water mark when Eddy Merckx went to Mexico City to attack the hour-record in 1972. He chose the venue because the reduced air pressure at altitude meant there was less aerodynamic drag. But having grasped that, his equipment selections were made entirely on the basis of weight – the headline feature of his round-tubed bike and its spoked wheels was that it weighed just 5.5 kg. It had holes drilled in most of its components to achieve that figure, the aero penalty of which almost certainly outweighed whatever miniscule gain he got from the weight saved.
It took till the 1980s for us to start to work it out. Merckx’s record was broken (pretty easily) in 1984 by the Italian, Francesco Moser, who used a skinsuit, aero hat and disc wheels. The wheels on their own probably weighed more than Merckx’s whole bike. Even cyclists started to get the message.
The insurmountable problem was that while we might have twigged that aerodynamic drag mattered, we had no way to actually measure it. In the 1980s and 1990s, you could probably have counted the total number of bike-riders worldwide who’d ever done any methodical aerodynamic testing (such as in a wind tunnel) on your fingers.
What we had instead varied from guessing, to copying other people’s guessing, to very home-spun testing. I spent several weeks in the early 2000s on a roll-down testing project – just freewheeling down a hill with a variety of configurations and seeing how far I ran out on the flat section at the bottom. It needed a calm day, but it produced results that more or less made sense. It was a very blunt tool, and a run was written off if a car passed you – although at least it was reassuring that the draft from the car showed up in the results. All the same, I ended up doing the runs at midnight to try to get the road to myself.
The next thing I did was just measuring frontal area – taking a head-on picture of myself on the bike in a variety of riding positions, and seeing what my projected area was. This isn’t all that off-beat – frontal area is the “A” that you notionally multiply by your drag-factor “Cd” (shape, basically) to get CdA, or total drag.
In a primitive era, I measured this area by printing the photos nice and big, then using a scalpel to cut away everything of the photo that wasn’t me, and weighing the remaining cut-out on a chemical balance.
You may laugh, but this probably put me in the top 20 cycling aerodynamics researchers globally. Everyone else was still using the balance to find the lightest brake levers. (You can do the same experiment now using a pixel-count, and it’s a moderately effective and very cheap tool.)
The first point at which it started to look vaguely scientific was with the first powermeters. You could get good results on the track, if you did long enough test runs, and you could even get passable results on the road if you didn’t mind doing so many repeats that testing two helmets would take a week.
Things have improved since, it has to be said. Wind tunnels have become reasonably accessible, if expensive. Track testing works too, using better software to cut down on the length of runs you need and the number of repeats. But both come with some limitations in terms of differences from the real world, and often with a price of several hundred pounds an hour.
In the end, the thing that we’re only just getting round to is reliable road testing. You need to gather large amounts of data, because it’s the only way to see through the noise of changing weather and road conditions. Being able to use something like the Body Rocket system on every ride is essentially what we’ve all been looking for for forty years, and can finally make aerodynamic drag a metric that’s as straightforward to track as power, speed or heartrate.
I just need to work out how to install it on a penny-farthing.