If you're still using 23mm-wide tires on your road bike, it's time to switch to 25mm or wider.

For a long time, 23mm tires were the preferred choice for road bikes. Many riders used even narrower tires, but in recent years, 25mm tires have become the most popular choice for both professional and amateur riders, with some even opting for wider. If you haven't made the switch yet, now is the perfect time. Let's look at why.

Comfort 

Under the same riding conditions, wider tires provide a more comfortable ride than narrower tires. They have a larger air chamber between the road and the tire, allowing wider tires to be run at lower pressures without the risk of pinch flats (where the tube gets pinched between the rim and the ground, causing a puncture). The lower pressure increases the amount of cushioning from the road, enhancing comfort.

Many top-level races are seeing this change, and it's believed that about 75% of riders in last year's Tour de France had switched to 25mm tires. This is for standard road stages, and riders often go even wider when tackling cobblestones.

Rolling Resistance

You want your tires to roll as easily as possible, but a certain amount of energy is lost due to rolling resistance. This is the energy it takes to deform the tire body where it makes contact with the ground. Many factors influence rolling resistance, including tire width, profile, pressure, material quality, and the thickness of the tire casing and tread.

Wider tires roll faster. "At the same tire pressure, the contact patch area of a wider tire and a narrower tire is the same. While a wider tire flattens across its width, a narrower tire is slimmer but has a longer contact patch. The flattened area can be seen as a counterweight to the tire's rotation. Because the flattened area of a narrower tire is longer, the wheel loses its roundness, causing more deformation during rotation. However, with wider tires, the radial length of the flattened area is shorter, and the tire remains rounder, leading to better rolling and thus faster speed."

Aerodynamic Performance

When it comes to aerodynamics, it gets more complex. While it's clear that narrower tires have a smaller frontal area than wider tires, the tire and rim together are not just an isolated tire.

In recent years, wheel rims have started to become wider, partly because tires are becoming wider.

"The trend of making wider rims comes from the trend of increasing tire diameter. This is especially true in competitive road racing. Wider rims provide mechanical support for larger diameter tires and are necessary to help reattach separated airflow to the rim."

Running a 25mm tire on a narrow rim creates an "ice cream effect," where a huge, inflated tire looks like it's sitting on a skinny rim. This mismatch between the two elements will not result in high levels of aerodynamic efficiency. However, wider rims are professionally designed for wider tires, allowing the rim to work aerodynamically with the tire. The separated airflow from a wide tire can reattach better to a wider rim than a narrow one, reducing drag.

Even if mounting a wider tire on a narrow rim doesn't improve aerodynamics, you might still consider it worthwhile for other reasons, such as extra comfort.