Many consider Mavic's Crossmax as the wheelset that began the aftermarket, prebuilt wheel revolution. Prior to that, discerning riders had to select rims, hubs, spokes, nipples, and a trusted wheelbuilder to construct a wheelset to their liking. What made that original Crossmax so successful some 20-odd years ago was the wheels were stiff, lightweight, and reliable, right out of the box. They were the wheels to own and if you scanned the start line at an XC race, at the regional and international level, the grids were full of them. Time marches on and Mavic has made significant changes since the non-tubeless, 26-inch, rim brake version and this latest version, the Crossmax Pro 29 Carbon Boost Wheel is brought up to speed and satisfies the needs of the modern cross-country rider with its Boost spaced hubs and full-carbon rim construction. These two features create a satisfying amount of lateral stiffness that’s welcome on 29ers as well as dropping rotational weight.
Mavic is notorious for being conservative in its wheel construction and it won't use a material unless it's certain that it's safe and has tangible benefits over other materials. Understandably, Mavic didn't quickly rush to get a carbon hoop to the mountain bike world until it was dialed. Newer rim technology like hookless beads allow for uninterrupted carbon fiber sections on the vertical rim walls instead of making a sharp 90-degree turn as on traditional bead hooks. This design not only increases the wheel's impact strength, but it also allows Mavic to drop grams. The additional benefit is it creates a better tire and rim interface, allowing the tire to take on a more natural profile and increasing its volume.
Mavic also leveraged its years of producing carbon road wheels to guide its meticulous lay-up schedule and precise resin impregnation, giving these composite hoops the reliability on par with its alloy rims. The lay-up itself targets radial give to help balance the inherent lateral stiffness of carbon with the forgiving vertical compliance of low-profile alloy rims. The lay-up benefits aggressive riders as it helps maintain contact with rougher terrain by absorbing impacts through engineered flex, resulting it less pinballing through the rock gardens, and keeping tires glued to the dirt. Boost spacing further quells lateral flex by spreading the flanges wider to improve the spoke bracing angle adding yet more drive stiffness to the already stiff wheel system—all without compromising the rims' propensity to dissipate shock.
That focus on traction, stiffness, and comfort is obviously well-suited to a tubeless setup, and Mavic's UST design—first developed in the late-90s—returns with some appropriately impressive developments. The most transformative is the before mentioned lack of a bead hook. In addition to handling bottom-outs with stoic aplomb, the XA Pro Carbon's hookless rim actually holds the tire more securely and reduces burping as well as making the install easier.
Tire retention, sans bead hooks, come courtesy of a more pronounced central channel and a pair of bead shoulders adjacent to that channel. These effectively keep the tire in place rather than relying on traditional bead hooks to keep the tire from blowing off. The central channel centers the tire and helps it seat while inflating, and the bead locks keep the tire bead in place so it doesn't unseat during hard cornering at low PSI. We should note here that tubeless-specific tires are, among other things, less prone to bead stretching, so we recommend sticking to them with these rims.
The rims' ability to damp bumps is further enhanced by the two-cross spoke lacing pattern, which might sacrifice a small amount of lateral or drive stiffness compared to three-cross spokes, but it also helps increase that bump compliance, so it’s a little more point-and-shoot and not so much tippy-toeing through technical terrain, while also better handling the torsional load transferred from hub to rim while slowing down with disc brakes.
As we've seen from its road lineup, Mavic demonstrates some XC-appropriate restraint with rim width, sticking to a tire-to-rim ratio that makes sense for practical applications rather than scoring on-paper points in the rim-width arms race. A bit of lateral fold in the tire actually benefits cornering, so the vertical sidewalls of the latest high-volume rims aren't necessarily the best solution for flowy handling. Instead of the 30mm+ rims we've been seeing, Mavic opts for a more appropriate external width of 28mm, which is better suited for XC rated rubber. Wider rims prevent the tire's shoulder knobs from biting into the dirt and exposing the side walls to sharp rocks and more exposure to puncture-inducing objects.
With all that technology-focused into the rims, Mavic doesn't leave anything to chance with hub duties and it utilizes its tried and true ITS-4 freehub design. With two sets of phased pawls, the design reduces engagement time, letting you quickly get on the gas at the start of a race or through techy sections. Sealed cartridge bearings keep contaminates out so the hubs spin freely season after season.
- Mavic's cross country wheels with all the modern accoutrements
- Carbon rim has engineered flex for comfort and traction
- Rim width supports XC tires for optimal handling
- Hookless bead burps less and makes tire installation easier
- Boost axles improve spoke bracing angle for better lateral stiffness
- Freehub with two pairs of offset pawls for quicker engagement
- Two-cross spoke lacing stiffens torsionally but gives radially