If you’ve been following the world of gravel racing, you’ve likely noticed an inflationary trend—not in entry fees, but in tire sizes. What started with 40mm tires as a standard has quickly ballooned to 45mm, 50mm and even 2.1-inch MTB tires on drop-bar bikes. The shift was most obvious during the 2024 Life Time Grand Prix, where a few riders, like Keegan Swenson, started dominating on tires that looked comically oversized. Soon after, the rest of the field followed suit.
But why are tires getting bigger? Is this just another fleeting trend, or is it a shift grounded in science and performance? And does it benefit casual riders as much as racers?
The science of rolling resistance
The move toward fatter tires isn’t just about aesthetics—it’s about performance. Traditionally, narrower tires were thought to be faster because they had less contact with the ground, reducing rolling resistance. But over the past decade, research has flipped that assumption. Wider tires, when run at lower pressures, can actually roll faster than their narrower counterparts on imperfect surfaces.
Andrew L’Esperance, a pro racer with a mechanical engineer degree explains:
“With a wider tire, you’re riding more on ‘top’ of the gravel versus ‘in’ it. This reduces rolling resistance on rough terrain. Plus, the increased volume allows the tire to conform to the surface better, improving comfort and reducing the chance of pinch flats.”
This is why world cup XC racers are now favoring 2.4-inch tires, and why road cyclists have largely abandoned 21mm tires in favor of 28-30mm options. The same logic applies to gravel, where the terrain is often unpredictable.
Why gravel tires are ballooning
Gravel racing is uniquely positioned to embrace wider tires. Without a long-standing tradition dictating tire widths, gravel bikes have evolved rapidly, with many now accommodating 2.2-inch MTB tires. While early adopters stuck to narrower 40mm tires, rough courses like Unbound and Big Sugar have pushed racers toward larger volumes.
Haley Smith, the 2022 Life Time Grand Prix winner, highlights the practical benefits:
“Wider tires let you float over rocky sections that might otherwise cause flats. They also absorb bumps better, giving you more compliance and control.”
For events lasting eight or more hours, the added comfort of wider tires can be a game-changer. Riders also report being able to ditch tire inserts, saving weight while maintaining durability.
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