The Bicycle Tires Right For You

For your bicycle tires, you want high puncture resistance, low rolling resistance, and low cost. Unfortunately you can only get two of the three, at best. Here's why.

A disclaimer to start out: don't be fooled by the tire weight and width illusion. Firstly narrow tires are lighter, have less rotational inertia and therefore the bike seem faster because it accelerates easily from a dead stop. During most of your ride, however, your accelerations will not be the whopping from 0-10 mph, but more like 10-13 mph or 18-20 mph, so the exhilaration of those accelerations is minor. Furthermore, at speeds above about 12 mph, air resistance becomes the overwhelming force, so tire weight is almost undetectable. Secondly, the high pitched buzz you hear from narrower tires at extremely high pressure seems fast, but producing sound means losing energy. With tires, the sound of speed is silence.

The counterintuitive phenomenon underlying both rolling resistance and comfort is suppleness of the tire. If the tire flexes to allow the bike to float over bumps there can be less lost energy than lifting the entire weight of bicycle and rider over every bump. Furthermore, using the tire as the main suspension means only the portion of the tire that is flexing is unsprung weight, so energy lost is all about the hysteresis in the tire. All elastic materials have hysteresis, meaning they absorb more energy than they give back on rebound, e.g., even the Superball doesn't bounce back as high as the height from which it was dropped. 

Tire hysteresis is kind of unpredictable, and depends on tire construction details like rubber compound, degree of unity between the various layers of cords and rubber, and bias ply angles. More, finer cords (more threads per inch or TPI), fewer layers, narrower tread and more sidewall flexibility all are generally associated with more ride suppleness. Thicker rubber, larger cords, more nylon layers and Kevlar belts under the tread all add puncture protection at the expense of flexibility and the trade off is readily apparent in rolling resistance tests. How well those components are put together and the inherent spring constant of the rubber compound are invisible when you are shopping for the tire. So you find a quality tire brand and model based on reviews and rolling resistance tests (bicyclerollingresistance.com is a nerdy one) and pick your width. The low hysteresis tires are the most expensive due to both manufacturing costs and consumer demand.

For a given model of tire, suppleness is a function of tire width and tire pressure. Translated to riding on real roads, wider tires at lower pressures are both more comfortable and produce lower rolling resistance. Obviously, the right combination of width and pressure depends on the granularity of the road or trail surface. Thus, there are road tires, gravel tires, and off-road/single track tires. For most roads, I like 28mm slick road tires, which are not bad for firm dirt or very fine gravel, but let me keep up with the other old codgers in my bike club on 20mph rides. For commuting through west-west through the heart of Cleveland, I did very well on 32-35 mm fine tread road tires with built-in kevlar belts under the tread. I averaged 12-15 mph, depending on traffic with a flat every other year or so.