Imagine the wheels of your bike are polygons. Then, to ride smoothly the road should be made of ‘catenaries‘ (yes, those bumpy things).
It is the math professor Stan Wagon who first demonstrated this concept with a real square-wheel bike at Macalester College in St. Paul, Minnesota.
Below a neat optical illusion involving a series of catenaries. The shadow depicts a biker who appears to be balancing on top of a series of sagging ropes (in fact, a chain or a heavy rope hanging from two points always delineates a catenary). Photo by Maurizio Lattanzio.