.zx-pdp { font-family: inherit; font-size: inherit; line-height: inherit; color: inherit; } .zx-pdp h4 { font-size: 16px; font-weight: 700; margin: 30px 0 8px; border-bottom: 1px solid #e0e0e0; padding-bottom: 4px; } .zx-pdp p { margin: 0 0 12px; } .zx-pdp ul { margin: 0 0 12px; padding-left: 22px; } .zx-pdp li { margin-bottom: 5px; } .zx-pdp a { color: #0055cc; } .zx-pdp .note { font-style: italic; font-size: 13px; color: #555; } .zx-divider { border: none; border-top: 1px solid #e5e5e5; margin: 32px 0; } .zx-press { border-left: 3px solid #111; padding: 14px 20px; margin: 16px 0 20px; background: #fafafa; } .zx-press .pc-quote { font-size: 14px; font-style: italic; color: #222; line-height: 1.7; margin-bottom: 6px; } .zx-press .pc-source { font-size: 12px; color: #777; font-weight: 700; } .zx-warn { border-left: 3px solid #b23b2e; padding: 14px 20px; margin: 20px 0 16px; background: #fdf6f5; } .zx-warn .ec-headline { font-size: 15px; font-weight: 700; color: #b23b2e; margin-bottom: 6px; } .zx-warn .ec-body { font-size: 13px; color: #444; line-height: 1.6; } 32mm internal. 54mm deep. Built around the tire instead of the other way around. Most gravel wheels are road rims that got a little wider. The 303 XPLR S isn't. Zipp started with the gravel tire — how it actually deforms, how it corners, what it does to the air — and built a rim to match it. The result looks more like an aero road wheel than anything gravel has seen, and it's the reason this thing is fast in a way rim depth alone doesn't explain. Escape Collective, testing the 303 XPLR platform, described the rims as "mind-bogglingly wide" — noting that at 32mm internal, Zipp had moved gravel rim dimensions somewhere the category hadn't been. — Escape Collective Why 32mm internal changes the tire Mount a 45mm gravel tire on a typical 25mm internal rim and the casing bulges outward above the rim like a lightbulb. That shape is why wide tires can feel vague at low pressure — the sidewall has to do too much work, so it folds under cornering load and the contact patch moves around under you. At 32mm internal, that same tire seats in a profile much closer to what the tire engineer actually designed: rounder, better supported at the sidewall, with a contact patch that stays where you put it. The practical outcome is pressure. You can run under 30 psi without the tire squirming, which means the casing absorbs the surface instead of transmitting it. Lower rolling resistance on rough ground, more grip in loose corners, and considerably less vibration reaching you over four hours. And the aerodynamics The rim is 40mm at its widest external point and 54mm deep. That matters because on a conventional gravel wheel, a 40mm+ tire is significantly wider than the rim beneath it — air hits the tire, separates, and never reattaches cleanly to the rim. Here the rim and tire form a continuous profile, so the airflow stays attached across the transition. That's real drag reduction at gravel race speeds, not a claim that evaporates below 25 mph. This is what Zipp means by Total System Efficiency: the wheel isn't optimized on its own, it's optimized as a wheel-and-tire system. Read this before you order: hookless, tubeless-only, 50 psi max These rims have no bead hook. That's what allows the profile to be shaped for aerodynamics rather than around a clincher hook, but it comes with hard rules you can't work around: Tubeless tires only. No tubed clinchers, ever. 50 psi maximum. Not a recommendation — a limit. Approved tires only. The tire must be on Zipp's approved hookless list for this rim. Not every tubeless gravel tire qualifies. 40c–61c only. Narrower tires are not approved on a 32mm internal rim, so this is not a wheelset you can put road rubber on. Check Zipp's current approved tire list before buying tires. Running a non-approved tire or over-inflating a hookless rim can blow the tire off the rim. The build Hubs: Zipp 76 front and 176 DB rear, with Center Lock rotor interface and stainless steel cartridge bearings. Straightforward, serviceable, and durable rather than exotic. Spokes: 24 CX-Sprint front and rear, laced 2-cross with brass nipples. Brass rather than aluminum is a deliberate durability choice — they don't corrode into the rim and they survive being re-tensioned years from now. Rim finish: UD carbon with adhesive decals. If you don't like the graphics, they come off with a heat gun and patience. 1,610g for the pair, tape and valves included in that figure. Driver body — choose carefully Available with either an XDR or Shimano HG driver. XDR — for SRAM 12-speed road and gravel cassettes with a 10-tooth small cog, including XPLR HG — for Shimano and SRAM 11-speed cassettes One important limitation: the 303 XPLR S cannot be converted to Shimano MicroSpline. Only the higher-tier 303 XPLR SW offers that. If you're running or planning a Shimano 12-speed drivetrain that requires MicroSpline, this is not the wheelset for you. Driver bodies are otherwise swappable, so moving between XDR and HG later is possible. Fitment Wheel size: 700c Axles: 12x100mm front, 12x142mm rear thru-axle Brakes: Disc, Center Lock Tires: Tubeless only, approved hookless tires 40c–61c Max tire pressure: 50 psi / 3.45 bar Max system weight: 298 lb / 135 kg, rider plus bike plus gear Confirm your frame clears a 40mm+ tire on a 40mm-wide rim before ordering. Because the rim is wider than most, a tire measures wider on it than it would on a narrower rim — a nominal 45c can come out closer to 47–48mm. Specifications Model: WH-303-XPS-A1 Rim construction: Carbon, hookless Rim depth: 54mm Internal width: 32mm External width: 40mm Rim profile: Symmetrical Rim finish: UD fiber, adhesive decals Hubs: Zipp 76 front / 176 DB rear, Center Lock Bearings: Stainless steel cartridge Spokes: CX-Sprint, 24 front / 24 rear, 2-cross Nipples: Brass Driver body: XDR or Shimano HG Axles: 12x100mm / 12x142mm thru-axle Weight: 1,610g per pair, including tape and valves Included: Tubeless tape, valves, 12mm front and rear end caps Warranty: Zipp lifetime warranty Setup These arrive taped with valves included, so setup is sealant and an approved tire. A compressor or high-volume floor pump makes seating a hookless bead considerably easier than a standard pump will. Seat the tire dry first and confirm the bead is fully and evenly seated all the way around before adding sealant. On a hookless rim this check matters more than it does on a hooked one. Start around 28–30 psi for a 45mm tire and work down from there. Most riders coming from narrower rims run these too hard for the first few rides and wonder what the fuss is about — the whole point of the platform is the pressure you can get away with. Always check Zipp's current approved hookless tire list before fitting tires. Zipp, XPLR, ABLC, and Total System Efficiency are trademarks of SRAM LLC. Quotation from Escape Collective's review of the Zipp 303 XPLR platform, referenced for context and not an endorsement of State Bicycle Co.