Tested: 2008 GT Marathon Pro Carbon

Price: $3,500

GT’s new marathon model was first released in 2007 under the i-Drive 4 Carbon moniker, but its name changed this year after GT replaced the aluminum rear triangle with one built from a carbon and aluminum composite. The new rear end is a third-pound lighter, and although it brought with it a new name, the bike’s purpose remains the same—to ride fast and long. The front triangle boasts swoopy, space-age lines, a large-diameter, radically shaped downtube and GT’s trademark seat-tube-pierced toptube, reminiscent of the company’s triple-triangle frame design.

The Marathon Pro includes a mix of reliable parts, the majority of which are well suited for 2 a.m. laps on a 24-hour course. Shimano XT disc brakes and XTR rear derailleur and trigger shifters deliver top-notch race-day performance. Ritchey components round out the cockpit while the whole package rolls on race-ready DT Swiss X1800 wheels fitted with Kenda Nevegal 2.1 tires. The tires grip admirably, but seemed prone to pinch flats and are not exactly race light.

On the trail, the i-Drive rear suspension excels at seated climbing over rough terrain and during out-of-the-saddle sprints, where pedal-induced bob was kept to a minimum. The frame’s racy design does come with some compromises, however. A short-stroke Fox RP23 shock saves weight, but gives the suspension a compression ratio close to 3:1. I rode most of the time with the shock rebound almost maxed out, and was sometimes left asking for more. When encountering successive medium-sized impacts, the bike’s four inches of suspension felt overpowered and began to buck.

Admittedly, those trails were better suited for a 5-inch-travel bike, but it’s interesting to note where a bike begins to reach its limits. The Marathon’s tight handling and responsive suspension are designed for the racecourse, where the light weight of a shorter-stroke shock makes for a nimble ride over smaller, higher frequency impacts. Despite all the efforts to build one heck of a high-tech frame the Marathon Pro still tips the scales around 27 pounds—nothing to brag about on the starting line. But swapping out the Nevegals for some lighter, racier rubber and a tubeless kit could easily help drop the Marathon’s weight.

The Fox Float 32 RL fork dishes out an ample 120 millimeters of plushness and includes a lockout feature for added firmness during tough sprinting or climbing efforts. You can argue that a 120-millimeter fork disqualifies the Pro as a full-bore race machine, but the Marathon’s name comes from a brand of XC events based on fortitude, speed and versatility. The Pro, like its broad selection of components, walks a fine line between racing and trail riding. —ALAN DAVIS

HIGHS: Seated climbing is a blast; Shimano components work well and are very durable.

LOWS: At 27 pounds it’s a bit hefty; rear suspension is overwhelmed by rough trails.

MORE INFO: 800-645-5806; GTBICYCLES.COM