Specialized prototype carbon mountain bike wheels spotted

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Specialized factory team rider bikes were fitted with prototype carbon rims for this year's races at the Sea Otter Classic. Specialized global marketing manager Nic Sims wouldn't say much about the new wheels ("They're Project Black!") but to our eyes, they look like a composite version of the company's existing Roval aluminum models.

Outer rim profile is similar with a roughly U-shaped cross-section and a flat inner wall supporting externally accessible alloy nipples. Given the relatively short sidewalls, we're guessing these new rims are also tubeless-compatible (with tape and sealant) similar to the NoTubes-like system Roval currently uses for easy conversions.

The aluminum hubs look to be standard Roval fare with straight-pull spokes – laced in a 2:1 pattern up front for more even tension between the two sides – a carbon fiber center section up front, and interchangeable end caps to maximize surface area contact on compatible forks.

In spite of the carbon construction, we expect these to be lighter than their aluminum counterparts but not dramatically so as the alloy rims were already very light. However, we are also expecting more significant jumps in stiffness and durability when these are eventually officially announced – we're guessing later this summer when Specialized holds its 2011 global launch. Stay tuned.