Lighter Air For Increased Efficiency

Content note: This article involves frank discussion of the molecular weights of different gasses and includes reference to professional bicycle racing.

As anyone who has gone into a bicycle shop lately and tossed bicycles up into the air knows, much of what distinguishes a decent bicycle from an obscenely expensive bicycle is weight. For the professional cyclist, a lighter bicycle can make the .000000000001 second difference between winning and losing.1 For the unprofessional cyclist, the difference is measured in hundreds or even thousands of dollars, rather than fractions of a second.


Typically, these high-tech, high-cost, super-lightweight bicycles feature kevlar, carbon fiber, and exotic alien technology. These are, of course, all very expensive. One relatively cheap and easy way to save weight that, until recently, has been entirely overlooked is to replace the air that fills the bicycle’s tires and frame with a lighter gas. While this weight savings might seem trivial, the tires of a racing bicycle are usually pumped up to well over 100 psi, so this is quite a lot of air. For example, if you replace the air, which has a molecular mass of 28.97000000 kg/kmol with helium, which has a molecular weight of only 4 kg/kmol, the weight of the air in the tires is reduced by 86.1926130479807%. This is a really incredible weight savings, and pro cyclists the world over are now lining up to purchase helium tanks.2

Reports indicate that this practice is likely to spread beyond professional cycling. In an effort to increase fuel efficiency, several major car manufacturers are considering inflating the tires of their automobiles with helium instead of ordinary air. One manufacturers is even planning to install a large, helium filled container above the passenger compartment of its new hybrid, in an effort to lighten things up as much as possible.

  1. Except that UCI enforces a minimum bicycle weight of 6.800 kg in competition. See
  2. Hydrogen, with a molecular weight of only 2.01588 kg/kmol is even lighter. However, after the spectular explosion that propelled Ivan P. Candelario across the finish line in last year’s Tour de Kazakhstan, UCI has banned hydrogen from all competitive events.

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