By Matt Pacocha

Travis Brown’s XOB prototype cyclocross bike uses a specialty belt made by Gates Rubber.

Photo: Matt Pacocha

That wasn’t just any old Trek XO cyclocross bike Travis Brown was riding in last weekend’s Boulder and Redline Cup races — it was a prototype belt-driven bike.

The Trek product tester first raced the anodized green machine, dubbed the XOB, at CrossVegas, held in conjunction with the Interbike trade show in Las Vegas.

The prototype X0B frame uses the standard X0 model’s front triangle, but replaces the normal chainstays with those from Trek’s T900 tandem and dropouts from the brand’s new ABP mountain bike suspension design. The ABP dropouts act as a concentric pivot on the suspension bikes and are mechanically linked. While they do not pivot on Brown’s Bike they are mechanically joined, allowing a one-piece belt to be fitted and for the eccentric cam to tension it. The stout chainstays made for a tandem resist compressive flex that could allow the belt drive to pop of its specialty chainring and cog under race-level power output. The ABP dropouts allow room for a mini-eccentric cam to hold the wheel and allow a very clean and effective way to tension the belt.

The oversized circular ABP dropout is borrowed from Trek’s new full-suspension mountain bikes.

Photo: Matt Pacocha

That belt, made of carbon-infused rubber by Gates Rubber, is the same belt sold through Carbon Drive Systems, popularized by Spot Cycles. Trek’s prototype-manufacturing shop made the cog and front ring that accommodate the belt.

Trek’s 2009 District commuter bike also uses belt drive. It’s low maintenance, clean, and won’t shred a commuter’s pants leg. Brown’s testing is intended to prove belt drive for use in competition — if it meets his approval, Brown’s 69er single-speed may be belt-equipped in 2010.

The frame uses tandem stays for stiffness and belt retention under stress.

The frame uses tandem stays for stiffness and belt retention under stress.

Photo: Matt Pacocha

Brown says testing is going well — he finished 15th and 18th in successive days of racing against the nation’s best gear-powered ’crossers — but he does have reservations about putting a non-repairable belt on a bike intended for all-day adventures.

If a belt breaks in the middle of nowhere — say, Porcupine Rim — and you don’t have a spare, that’s a problem. It’s less of an issue in ’cross, where a pit is usually only a half lap away.

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