Editor’s Note: This article originally appeared in the July/August issue of VeloNews magazine.
Knobs, grooves, hexagons, ridges: The tread pattern of a gravel tire is covered in protrusions to give it traction, evacuate mud and water, and stand up to harsh terrain. How does a tire manufacturer know how to arrange all those rubber bumps?
The process requires artistry, physics, and a lot of trial and error.
“There is no magic cell phone app that you tell to design this tire for this application,” says Ken Avery, vice president of marketing and product for Vittoria Tires. “You have to talk to a lot of people, gather a lot of data, and look at how a tire is going to interact with a certain type of surface.”
Tires are often designed to perform across several surface types. Thus, they must balance multiple attributes: low rolling resistance with cornering grip, for example. Designers create effective edges to dictate how much grip a tire has, given whether it is propelling you forward or braking your speed.
Ultimately, designing a tire’s tread pattern starts with knowing its application. Johs Huseby, global director of OEM sales at WTB, also oversees product vision. He says 25 or more iterations of a tire may be designed before a final pattern is settled on.
Before a tire reaches a consumer, Vittoria uses pro athletes to test a design. For its Terreno Dry, its cyclocross racers told designers they loved a file-tread tire, but when they braked they’d always skid. The tire’s hexagonal pattern was born: in the rolling direction, the pattern creates hundreds of little ramps, giving it a slick feel. Under braking, the effective edges stand up.
“This doesn’t happen in a vacuum with myself,” says Avery, who has 20 years of tire design experience. “There’s an army of athletes that verify each round of prototypes to make sure we’re on track. Before we release it, they’ve already raced on it many times.”
Early gravel tires were more a mashup of chunky MTB treads and road tire casings. Now, there are more sophisticated choices, as designers learn what works.
Huseby sees a trend toward faster rolling tires for racers, which incorporate a smooth center section with side knobs to improve cornering.
Popular all-conditions tires feature dense tread patterns. “With their low height, you get low rolling resistance, and lots of little fingers that reach out to get traction,” Huseby says.
Some brands go further, producing 35-45-millimeter tires with very little tread. That’s because consumers are starting to realize they don’t need a lot of tread on a gravel bike to still get a decent amount of traction.
“Because you can run such low pressures, you’re achieving grip that way rather than through tread,” Huseby says.