Why a lighter bike doesn’t make you faster

By Felix Salmon
August 22, 2011
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.

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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.

(Via Vanderbilt)

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Comments
8 comments so far

If you’re really worried about doing a 27 mile commute in a quick time, surely you should just leave your bike in the garage and dri…..nah, forget it.

Posted by ottorock | Report as abusive

My experience with this sort of thing was moving from a Walmart-style sub-$100 bike to a decent $300 bike, back when I was first at the university. I do doubt that there was that much difference in speed between the two, as I rode pretty fast either way. However, I am pretty darned sure I expended one heck of a lot less energy on the better bike, not so much because it was lighter, but because it had much better lubrication/bearings. The ride was vastly more comfortable on the $300 bike.

My bet is that in moving from a $300 bike to a $800-$1000 bike is probably a much, much smaller change from the Walmart-style bike. I would highly recommend the move, at least, to the $300 bike or somewhere thereabouts, to anybody that uses a bike on a frequent basis.

Posted by JasonDick | Report as abusive

“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 think you’re really stretching here (slow news day?), this model doesn’t fit at all, let alone ‘perfectly’. Speed on a bike is related to power output, that’s it. Bike handling skills are pretty much orthogonal to power output, exerting more effort to generate more watts has absolutely nothing to do with what Fitts and Posner were talking about.

Posted by inboulder | Report as abusive

This is similar to speeding from stoplight to stoplight in a car. it is quite possible that all of the gains are wiped out by the pauses at each intersection and that it has very little to do with riding skill.

Posted by 6ft6 | Report as abusive

Where you’ll actually see a difference is in crankset and wheel size, for example moving from a converted mountain bike style commuter to a road bike. I’m not an accomplished cyclist and even I can top out my non-road gearing on even slightly downslope grades.

And while the frictional resistance between high and low end road tires isn’t much there should be public service announcements telling anyone with knobby off road tires to invest the $15 in slicks.

Posted by pnelson | Report as abusive

Agree with pnelson, smooth tires make a noticeable difference. I ride a very heavy commuter bike and after I upgraded to a pair of smoother, higher-pressure tires, I noticed I was able to scale hills in higher gears and I was arriving at the BART station about a minute earlier than I had been with the old tires.

Posted by marijane | Report as abusive

This is pretty cool, as I’ve always suspected that the weight of a bike doesn’t have that much impact for your average cyclist. The delta between a heavy and light bicycle is pretty small compared to the weight of the rider and his/her pack. Indeed, if I decide to bring home one hard cover book from the office, I would pretty much erase the advantage of my carbon-fiber forks.

As someone who often times my bike commutes I would concur that external factors (wind, lights, traffic) can make a big difference, even taking into account my speedometer doesn’t time when I am stopped. I would guess, given the ‘sample size’ (# miles ridden, # commutes)that these factors wash out over the sample period. The graph shown seems to have a lot of scatter.

I think the big factor not discussed is that carbon-fiber delivers much more stiffness per pound than steel. A stiffer frame delivers more power to the wheels and less to flexing the frame. Unless you are really pushing it, the stiffness pay-off (or any weight pay-off) is not going to show up for your typical commuter.

Posted by JimInMissoula | Report as abusive

I had similar experience. I have a 1980′s Nishiki touring bike with a chromoly frame that is 30-plus pounds. The tires are 28′s. It’s a large bike (I’m told it’s too big for me by all the bike shops). I recently got a 56cm Cannondale CAAD8 and the tires are 25′s. This bike frame is aluminum and the bike weighs about 20 pounds. It’s no faster on most terrains and is slower on downhills. It does get up hills easier and perhaps a little faster. I love both bikes but was surprised that the Cannondale wasn’t quicker and faster (that’s what I bought it for). The chromoly frame feels more responsive and quicker than the aluminum. I couldn’t afford carbon.

Posted by TomBisson | Report as abusive
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