Reynolds Blacklabel 309/289 XC Boost Wheelset

Cross-country mountain biking has changed. Wider tires, lower pressures, and increasingly technical course designs have pushed XC wheels beyond the narrow, fragile constructions of the past. The Reynolds Blacklabel 309/289 XC Boost Wheelset is Reynolds' response — a carbon tubeless wheelset that applies DH-derived impact resistance technology to an XC-weight package, built for riders who want the efficiency of a carbon XC wheel without the anxiety of babying it on technical terrain.

The "309/289" designation reflects Reynolds' front-specific and rear-specific rim design. The 309 front rim runs a 30mm internal width; the 289 rear runs 28mm. Both are 21mm deep, hookless, and tubeless-ready. The width difference is deliberate — the wider front rim improves lateral tire support for steering input and cornering traction, while the slightly narrower rear prioritizes strength and power transfer efficiency under load. Both rims are built using Reynolds' IDM (Impact Dispersing Matrix) layup combined with MR5 (Mountain Rim 5) construction — the same technologies found in their downhill wheels. The result is a carbon rim with genuine impact resistance, backed by a lifetime warranty.

The hubs are the Reynolds and Industry Nine Blacklabel Hydra — fully CNC machined and built around I9's 6-pawl engagement system that produces 0.52° of engagement per rotation. In practical terms, that is immediate power pickup. There is no discernible ratchet delay between the pedal stroke and the drivetrain engaging, which matters most in technical XC terrain where a precisely timed pedal stroke into a corner or over an obstacle requires an instant mechanical response. Spokes are Sapim CX-Ray — bladed, cold-forged, and among the lightest high-tension spokes built. Spoke count is 24 front and 28 rear. Brake interface is Center Lock; axles are Boost standard — 15x110mm front and 12x148mm rear. The complete wheelset weighs 1,468 grams: 689g front, 797g rear.

Design Benefits

1. IDM + MR5 construction with lifetime warranty. Reynolds' Impact Dispersing Matrix layup is engineered to spread impact energy across the rim structure rather than concentrating it at a single point — which is where most carbon rim failures originate. Combined with the MR5 Mountain Rim 5 construction architecture, this produces a carbon rim with impact resistance that Reynolds originally developed for their downhill program. The lifetime warranty is the measurable output of that engineering investment.
2. I9 Hydra hub — 0.52° engagement. The Blacklabel Hydra hub uses six spring-loaded pawls in a sequential engagement design that produces 0.52° of pickup per rotation. This is as close to instantaneous engagement as currently exists in production hub design. The practical benefit is most apparent in technical terrain: every pedal input transfers immediately, with no dead zone between stroke and drive.
3. Front/rear specific rim widths. The 309 front runs a 30mm internal width; the 289 rear runs 28mm. This is not a cost-saving symmetry decision — it reflects the different functional demands of each wheel. The wider front rim supports the tire more laterally for improved cornering confidence. The slightly narrower rear optimizes rim strength and spoke bracing geometry under the sustained power demands of the drive side.
4. Hookless tubeless construction. The hookless bead profile eliminates the bead hook from the rim cross-section, reducing rim weight and allowing the tire to conform to the rim for better compliance and lower optimal pressures. Tubeless-ready out of the box — run sealant, eliminate tubes, and reduce both rotational weight and pinch flat risk. Important: hookless rims require tubeless-compatible tires. Verify tire compatibility before mounting.
5. Sapim CX-Ray spokes. The CX-Ray is Sapim's top-tier bladed spoke — elliptical cross-section, cold-forged, double-butted, and one of the lightest structural spokes available at any price. Used across high-end road and MTB builds where weight and fatigue resistance both matter. The 24/28 spoke count provides adequate redundancy for demanding terrain without the weight penalty of a higher count.
6. Boost axle standard. The wider Boost spacing — 15x110mm front and 12x148mm rear — increases the distance between hub flanges relative to the rim centerline on both wheels. This improves spoke bracing angle, which directly translates to better lateral stiffness and load distribution. The standard is now universal across performance mountain bikes, making these wheels a drop-in fit for modern builds.

Final Take

The Reynolds Blacklabel 309/289 XC Boost Wheelset is built for the XC racer or aggressive trail rider who has outgrown the limitations of standard carbon wheelsets. At $2,299.99, you are investing in I9 Hydra hubs with 0.52° engagement, Reynolds' DH-derived IDM rim construction, Sapim CX-Ray spokes, and a lifetime warranty on the carbon — all on a wheelset that weighs 1,468 grams. These are purpose-built tools for riding XC the way it is now being raced: fast, technical, and unforgiving of equipment that can't keep up. Available in Shimano Microspline, Shimano/SRAM HG, and SRAM XD driver configurations.