One surprising discovery is wider tires roll faster. The science is in the tire’s deflection. Under the load of the rider, the tire is flattened against the road, creating the shape of the tire patch in contact with the terrain. Narrow tires have a long, skinny contact patch and as a tire gets bigger, the contact patch shortens and gets wider. The shorter, wider contact patch improves rolling resistance while actually offering better cornering traction. The trend of wider tires is taking advantage of these benefits.
In addition, you can run lower air pressure without running the risk of a pinch flat. The lower pressure increases the amount of cushioning you get from the tire, and can further improve ride comfort. However, there is a balance to consider when dropping tire pressure because lowering air pressure can sacrifice rolling speed. For many, the cost of a few watts in rolling resistance to improve comfort on rough road rides is an acceptable trade off while others like to maximize the energy they put in and keep the pressure high.
It’s important to note that to fully get the benefits of a wider tire, you need a wider rim. The inner rim width, where the tire is actually mounted to the rim, needs to match up with the tire width to give it the correct profile. Mounting a wide tire on a narrow rim squeezes the tire at the bead. This won’t provide the proper tire profile and changes the contact patch shape, negating the full benefits of a larger tire. Furthermore, the aerodynamics of the rim profile needs to blend with the tire so it’s imperative to have the correct rim geometry for wider tires.