The Air Check That Saves Pedal Power

Before a ride along a paved canal path, checking bicycle tires might seem less important than packing water. Yet a quick pressure check can make pedaling easier if the tires have become too soft. The reason is not that added air pushes the bicycle forward. Instead, the right amount of air helps keep the tires from wasting the rider's effort.

When a bicycle carries a rider, each tire flattens a little where it touches the ground. As the wheel turns, one patch of rubber bends and then returns to its shape. The next patch does the same. A tire with too little air flexes, or bends, more. Some of the rider's energy becomes heat as the rubber changes shape. That leaves less energy available to move the bicycle ahead.

This bending is one source of rolling resistance, the force that works against a rolling wheel. Proper air pressure supports the tire so it does not squash as much. The rider then spends less effort overcoming this kind of resistance. This explains why adding air to an underinflated tire can make the same smooth path feel easier, even without changing gears.

Imagine a side-view drawing of two tires carrying equal loads. One tire has a wide, squashed bottom; the other keeps more of its round shape. The caption reads, “Too little air allows more bending.” The drawing helps explain the point by showing a change in tire shape that a rider might overlook.

How can a rider know whether a tire needs air? A pressure gauge measures the air pressure inside. It gives stronger evidence than a quick squeeze with a hand. A tire can feel firm to a hand and still be below its needed pressure. For example, imagine a tire marked for a range of 35 to 50 pounds per square inch, or psi. A gauge reading of 20 psi shows that this tire is below its listed range. With an adult's help, bringing it to an appropriate pressure within that range, such as 40 psi, corrects that problem.

Checking once is not enough for the whole season. Air can gradually escape through the tube and valve even when there is no obvious hole. A bicycle that felt fine on the last ride may have softer tires later. A fresh gauge reading can reveal that hidden change.

More air, however, is not always better. Tires should stay within the manufacturer's recommended limits, and a suitable pressure also depends on the rider, bicycle, and surface. On a rough path, an overly firm tire may bounce over bumps instead of rolling smoothly. The useful habit is checking for an appropriate pressure, not pumping in as much air as possible. A small check can prevent some unnecessary work on the next ride.