Gravel wheels face a fundamental tension between aerodynamic efficiency and the wider tire clearances that off-road riding demands. Zipp's 303 XPLR S addresses this with a 32mm internal rim width paired with a 40mm external dimension —wider than most mountain bike rims and built around the premise that the tire and rim should function as a single aerodynamic unit rather than two separate parts. The hookless bead design creates a smoother interface with approved tubeless tires, allowing pressures well under 30 psi without the squirm or pinch flat risk that narrower rims introduce at those pressures.

Rim depth sits at 54mm , which treats aerodynamics as a gravel concern rather than a road-only one. At average race speeds of roughly 29-36 kph, Zipp's internal testing found 2-watt savings from aero efficiency gains compared with a peer wheel, with the advantage growing to 10 watts or more when speeds exceeded 53 kph on descents and other fast sections. The depth is meaningful for riders chasing Unbound-style finishing times on mixed surfaces, and the wide profile keeps the rim-tire transition clean rather than lightbulb-shaped.

Critical compatibility note: the 303 XPLR S is only compatible with an approved tire list. The Goodyear XPLR Slick and Goodyear XPLR Inter are specifically designed and optimized for the 303 XPLR S , and Zipp's approved list also currently extends to the Zipp G40, Zipp Tangente, and Schwalbe G-One models in 40mm and wider. Mounting a non-approved tire to these rims is not supported by either Zipp or the tire manufacturer. If you're not prepared to run one of the approved options, this isn't the wheel for you.... Read More