Which Gravel Tire Is Actually Faster? Two Testers Settled It With Real Data

Skinny tire or wide tire. Slick or knobby. It's one of the oldest debates in gravel riding, and it usually gets settled by feel, a Strava segment, or whatever the fastest person in the group ride happens to be running.

Cycling journalist Ben Delaney and tire tester John Karish decided to settle it properly. Over two days on two very different Colorado gravel surfaces, they ran a controlled test comparing four tires, including two widths of the same Schwalbe RS Pro model and two versions of the Schwalbe Rick XC. Their protocol combined the Chung method (a way of calculating rolling resistance and drag from ride data instead of a lab) with real aerodynamic measurement, which is where AiRO came in. You can watch the full test here: Gravel Tire Testing: Skinny vs Wide, Slick vs Knobby.

Why Rolling Resistance Testing Needs Real Aero Data

The Chung method works by measuring everything it can, tire rollout, speed, power, air density, wind, and system weight, and solving for whatever's left unknown. To isolate rolling resistance accurately, you first have to account for aerodynamic drag. Guess wrong on CdA and the whole model skews, making a flat road look like it's sloping downhill or up.

That's the piece Karish used AiRO to solve. Rather than booking wind tunnel time, he and Delaney each ran their own rider photos through AiRO's platform, adjusting position details like elbow width, hand position, and helmet angle until the model matched their actual riding position. AiRO's CFD analysis then calculated each rider's CdA, giving them a real, individualized aero number to plug into the rest of the equation instead of an assumption.

Karish, who has published rolling resistance data on more than 70 tires, called it a way to get a wind tunnel number without a wind tunnel, and noted that AiRO's founder has validated the platform's output against wind tunnels directly, including work with Olympic speed skaters chasing hundredths of a second.

What They Found

The results depended entirely on the surface, which was the whole point.

On hard-packed, magnesium-chloride-treated dirt, a smoother, faster surface, the numbers came out close to even: both the 45mm and 55mm RS Pro tires required about 206 watts to hold 35 km/h once aerodynamics were factored in. The wider tire rolled slightly better, and the narrower one was slightly more aerodynamic, and the two effects canceled out.

On rough, loose gravel, the story flipped. The 45mm tire required 294 watts to hold that same speed. The 55mm version needed only 271 watts, a 23-watt savings, aerodynamics included. The knobbier Rick XC saved 16 watts over the 45mm tire on the same surface, but still came in behind the wider slick.

The takeaway wasn't "bigger is always better." It was that the right tire choice depends on the surface, and the margins are big enough to matter once you can actually measure them.

Why This Matters for Fitters and Riders

This test is a good example of what AiRO is built for: giving people outside a lab or a wind tunnel a real, individualized aerodynamic number they can use to answer a practical question. Karish and Delaney weren't AiRO customers running a sponsored test. They were independent testers who needed accurate rider CdA to make their own methodology work, and reached for the platform because it got them there without the cost or scheduling of a wind tunnel.

Watch the whole video here: Youtube. If you're a fitter curious about adding aerodynamic testing to your own studio, or a rider wondering what your own position is costing you, find an AiRO-approved fitter near you.