While American wheel manufacturers play fast and loose with rim widths and layup, Mavic has held firm in its stance that safety and proven design take sole precedence over flashy trends. So with Mavic finally going full carbon with its XA Pro Carbon 27.5in Wheelset, you can rest assured that the brand would not have released it if it hadn't thoroughly vetted the design to handle the kind of trail abuse garnered alongside today's breed of hard-charging, 5-in sleds.
In typical Mavic fashion, the XA Pro Carbon wheels are shot-through with an expansive list of technologies whose ultimate aim is to increase drive stiffness without taking away from the rim's slightly compliant bump absorption— speed that privileges comfort. Or comfort that privileges speed, if you'd prefer. Ultimately, the wheels strike one of the best balances of efficiency and cushion in the trail market, and they do it while foregrounding Mavic's insistence on safety and reliability. Despite that staid approach, the XA Pro Carbon does represent a pretty drastic change to Mavic's mountain wheel philosophy, so there's a lot to cover; however, since the wheels are built with one of Mavic's first full carbon rims, that seems the most appropriate place to start.
The rims feature a lay-up that targets radial flex to balance the inherent lateral stiffness of carbon with the forgiving vertical compliance of low-profile alloy rims—or, in other words, to allow a little bit of squishy cush for gnarly runs. We like stiff wheels while hammering, but wheels that are too stiff present issues beyond just comfort. Cushion aside, the lay-up's real benefit to aggressive trail riders is that it helps maintain contact with lumpy terrain by absorbing impact through engineered flex, which means it bounces less and keeps tires glued to the dirt. That focus on traction, stiffness, and comfort is obviously well-suited to a tubeless setup, and Mavic's UST design returns with some impressive developments.
The most notable of these updates is the lack of a bead hook, which improves impact resistance by eliminating the fragile bead shelf and ensuring that structural integrity isn't compromised by post-production machining. Instead of that delicate construction, the XA Pro Carbon features 3mm of impact-resistance that compares favorably to the usual 1.2mm thickness of alloy rim walls. Eliminating the hook also reduces production costs by either eliminating the machining step or, if manufacturers are molding the bead hooks, by reducing the number of factory rejects. Bead hooks are precise constructions, and it can be difficult for even manufacturers of Mavic's caliber to perfectly stuff that much material into such a claustrophobic mold and still meet the minute tolerances that we expect from the yellow label. We trust Mavic because the brand has consistently placed rider safety ahead of mindless pursuit of innovation trends. Adopting the hookless bead inverts that model, but for the same reason: safety first.
The hookless rim has a final, counter-intuitive benefit: In addition to handling bottom-outs with stoic aplomb, the XA Pro Carbon's hookless rim actually holds the tire more securely and reduces compressor blow-offs and on-trail burps. The rim owes these properties to two features not included in rims with bead hooks: a more pronounced central channel and a pair of bead locks, not hooks. These two additions more effectively divide the duties of traditional bead hooks. 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 rim changes extend beyond the hookless construction. Instead of being hidden behind an undrilled inner wall, which made truing a pain, the spokes now thread into conventional nipples that are exposed in the tire bed. This means rim tape, which we don't mind installing (and comes already installed). The holes are drilled asymmetrically, which improves the spoke bracing angle at the flange for more lateral stiffness that doesn't hamper the rim's engineered radial flex. The spokes are also stainless steel instead of Mavic's ultralight, ultra-stiff Zicral aluminum. And that's a good thing, because steel spokes encourage that forgiving radial compliance while Zicral—which is ideal for lightweight climbing wheels—all but erases it.
The rim's ability to damp bumps is further enhanced by the two-cross lacing spoke lacing pattern, which does sacrifice a small amount of lateral or drive stiffness compared to radial spokes, but it also increases that bump compliance, requires less baby-sitting without risking spoke failure, and (most importantly) better handles the torsional load transferred from hub to rim while stopping with disc brakes.
As with its road line, Mavic demonstrates some 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 side walls of the latest high-volume rims aren't necessarily the best solution for flowy handling. Instead of the 30mm+ rims we're seeing crop up in droves, Mavic opts for a more modest 26mm width, which lets 2.4in tires strike a balance between the dome-like gumdrop shape of ultra-wide rims and the overly floppy lightbulb bulge off wide tires mounting on narrow rims.
- A trail wheelset that charges eagerly into all-mountain territory
- Carbon rim boasts engineered flex for cushion and traction
- Rim width lets mid-sized tires sit perfectly for flowy handling
- Hookless bead burps less and makes tire installation easier
- Freehub with two pairs of offset pawls for 7.5-degree engagement
- Two-cross spoke lacing stiffens laterally but gives radially