June 11, 2013
There's never been a bicycle since John Dunlop's pneumatic tire (1887) that actually touches the ground. We ride cushions of air with a floating sensation that hugely reduces rolling resistance and delights the child in us. Levitation is not just for the imagination.
The wheel was a seminal invention for mankind, transforming our terrestrial mobility, multiplying our nomadic tendencies a thousandfold. Much later, the use of tension was the wheel's most important structural enhancement. But the pneumatic tire gave it wings. Unquestionably, the pneumatic tire was the most significant improvement in the history of wheels. What an idea, floating around on compressed air!
In order to retain a pneumatic tire system wheels provide important features: holes for valves, wells and lips to grip the tire, resistance to massive compressive forces of inflation, easy wheel dismounting for flat repairs. All of these occupy much of the design and weight of a wheel. In fact, the wheel is not just a platform for the tire but an integral component of the pneumatic system.
The more I study wheel design the clearer it becomes how important are tires. Nothing so affects your ride as the tire. It trumps rim, spokes, hub, and tension with a particular combination of sidewall flexibility, tread composition, air pressure, weight, and size. For example, mountain bikes are more about large tires than any of their other features. Tires are magical the closer you look.
The Living Tire
For one, the very use of an endless bladder to capture and store air is downright organic. The tire is a sausage, a worm, a snake, just ask the Flintstones. This resemblance is more than superficial. A tire is a genuine imitation of living tissue. Tissues like arteries and intestines are remarkable structures. They are flexible, elastic, and yet do not become oversized. The elastin of living tissue resembles the rubber of tires. Collagen fibers play the role of the textiles so important in tire construction. Together you have capacity for tremendous deformation, strength for high pressure, and damage resistance.
Next time you float above ground on your 2-wheel levitation machine, think what a great extension of your body it is. Not only the ergonomics but also features alive with energy and potential.
Art of the Tire
Even the manufacture of tires is a subtle art. First, there's rubber. Where does rubber come from? Originally from tropical trees, their elastic sap, latex. Today we have synthetic rubbers but all tire manufacture is as close to natural sources of rubber as possible. And rubber is hugely, frustratingly complex.
Unlike many modern, engineered materials (metals, chemicals), rubber is more akin to wood and leather. Even the synthetic versions are highly variable with a giant range of density, springiness, durometer, efficiency, resistance to weather and friction, and aging properties. Rubber ages almost as if it were living. Well, much of it was.
How can modern tires can be so precise and uniform, so dainty yet rugged, so reliable and long lived? As wheel people, we (fellow readers) embrace tires like none of the other specialists. Frame folks, drive train experts, cockpit physiologists, aerodynamic authorities, brake and suspension system masters; no one can lay claim to the wonders of the tire like wheel people.
After all, the wheel is not just a mounting point for the tire like a downtube is for a front derailleur. No, wheels are integral to the pneumatic system. Tires and wheels share secrets the rest of the industry will never know!
Next, a few of the tire's secrets revealed, then on to Trick 3, brakes.
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