Why a lighter bike doesn’t make you faster
I’m very late to Jeremy Groves‘s wonderful little paper where, using himself as a subject, he timed his bike commute on a heavy steel bike and on a much lighter carbon bike. After riding 1,520 miles back and forth from Sheffield to Chesterfield Royal Hospital and carefully timing every journey, he came to an inescapable conclusion: the lighter bike wasn’t any faster than the heavier one. And this on a long journey where small differences would, you would think, add up: the round-trip commute was 27 miles long, with 2,766 feet of total ascent. That’s the kind of uphills where saving 9lbs of bike makes a real difference.
So, what’s going on here? Groves has his own theories, mainly surrounding the idea that big factors, like the weight of the rider and the amount of drag, completely obliterate smaller factors like the weight of the bike and the resistance of the tires. But I think there might be something else going on, too. Here’s Joshua Foer on what he calls the “OK plateau”:
In the 1960s, the psychologists Paul Fitts and Michael Posner described the three stages of acquiring a new skill. During the first phase, known as the cognitive phase, we intellectualize the task and discover new strategies to accomplish it more proficiently. During the second, the associative phase, we concentrate less, making fewer major errors, and become more efficient. Finally we reach what Fitts and Posner called the autonomous phase, when we’re as good as we need to be at the task and we basically run on autopilot. Most of the time that’s a good thing. The less we have to focus on the repetitive tasks of everyday life, the more we can concentrate on the stuff that really matters. You can actually see this phase shift take place in f.M.R.I.’s of subjects as they learn new tasks: the parts of the brain involved in conscious reasoning become less active, and other parts of the brain take over. You could call it the O.K. plateau.
The skill of riding a bike fits perfectly into this scheme. It’s not easy to learn at first, but over time we get better at it, until we’re so good at it that we basically stop thinking about it, and stop trying to get any better than we are. I’m sure that a doctor like Groves has much better things to think about on his commute than his bicycling technique.
When I switched from a heavier bike to a lighter one, I felt as though I was going faster, but I have no idea whether that’s empirically true. Certainly the lighter bike is much more maneuverable, which is very handy on New York’s potholed streets. And it’s easier to get up hills, even if I’m not getting up them any faster.
As Kent Peterson notes, a lighter bike can make your journey more comfortable. That doesn’t mean it will make your journey more comfortable: ultra-light racing bikes in fact tend to be rather uncomfortable things. But when you’re riding up a hill at your normal speed, you’re generally happier when you weigh less. That’s why people buy lighter bikes: at the margin, they’re likely to make any given bike ride a little more pleasant. Which is not the same thing as saying it’ll be faster. Leave the racing to the racers: the rest of us are just happy being happy.