TRUE OR FALSE? The skinnier the rider, the faster the bike
This can be TRUE and FALSE.
TRUE, because skinnier and smaller riders have a smaller frontal area and therefore less aerodynamic drag. (But they can also produce less power so they need to use this lower aero drag to their maximum advantage).
And yes, it’s also FALSE! Additional volume in the right place can actually be beneficial. We call this the ‘Aero Belly’… A belly has been shown to be beneficial for aerodynamics as it better streamlines the airflow around rider’s torso! So next time you ride with someone with a big belly, there is also a partial positive aerodynamic aspect to their larger proportions!
A quick history lesson: Fränk Schleck once rode a Tour de France time trial wearing a back-to-front hydration pack on his stomach, under his race suit. The claim at the time was that it saved him 2” per kilometre. Wind-tunnel tested or not, the UCI quickly banned any such tactics.