How does a bicycle stay upright?
(Image: Matthew Richardson)
We thought we knew the maths behind cycling. We were wrong – and our efforts to figure it out are leading to some weird and wonderful new bike designs
In 2011, an international team of bi-pedal enthusiasts dropped the bombshell that, despite 150 years of analysis, no one knows how a bicycle stays upright. Across the world, riders dismounted and stared at their bikes in disbelief. What they had been doing for years was a feat inexplicable by science.
Well, sort of. “What we don’t know are the simple, necessary or sufficient conditions for a bicycle to be self-stable,” says Andy Ruina, an engineer at Cornell University in Ithaca, New York.
We have relied on trial-and-error engineering to construct stable bikes that aren’t prone to toppling while in motion. Explaining how they work mathematically requires around 25 variables, such as the angle of the front forks relative to the road, weight distribution and wheel size.