Gravel racing has pushed rim widths into territory that would have seemed absurd five years ago, and Zipp's 303 XPLR S sits at the leading edge of that shift. The wheel offers an enormous 32mm internal rim width with a 40mm external dimension — wider than the current status quo in mountain biking , paired with a 54mm depth that treats aerodynamics as a gravel concern rather than a road-only one. The geometry is built around a specific idea: start with the tire, then design the rim to disappear behind it.

That thinking drives the hookless, tubeless-only construction. The deeper and wider rim design means better aero performance — at average race speeds of roughly 29-36kph, 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 53kph on descents and other fast sections. More practically, the wide profile increases air volume, allowing for lower tire pressures without squirm, mitigating surface vibrations while maintaining grip when cornering or traction while climbing.

Compatibility is the catch, and it's a real one. The 303 XPLR S is compatible only with approved tires — the Goodyear XPLR Slick and Goodyear XPLR Inter are specifically designed and optimized for the platform. The 32mm internal bed is wide enough that narrower gravel tires square off unpredictably, so Zipp maintains a published list of approved rubber. Before committing, check that your preferred tire is on that list — running an unapproved tire on a hookless rim this wide isn't a gray area.