In a vacuum, it's easy to classify a mountain bike: measure the head tube angle, check the reach, and check the depth of travel. But vacuums suck, and Pivot's re-imagined Mach 5. 5 Carbon Race XT 1x Complete Mountain Bike refuses to so easily be classified. It's titular 5. 5in of DW Link travel and Switchblade-esque reach may suggest pure all-mountain bike at first, but the head tube angle rides the boundary of what we'd consider enduro slack. The bike is finished with a selection of kit from Shimano and Race Face. The build may lack the golden sheen of current one-by royalty, but makes up for the absence of shiny bling with the kind of bullheaded durability that better survives the occasional digger. The slack head tube and surprisingly deep-feeling travel reward aggression in chunky stuff, but our favorite part of the bike may be the rear triangle. Or rather, it's what's happening between the rear and front triangles; DW-Link may never have shined brighter than on the Mach 5. 5. It combines the same pivot cartridge bearing featured on models like the Phoenix, but it ditches the clevis altogether. That makes for less weight, a tighter back end, and a light-off-the-top feel that stays glued to the trail--a trait only enhanced by the addition of mid-plus tires and a steep seat tube. We expect a bike with such a long cockpit and a 66. 5-degree head tube angle to leave us giddy on descents, but the suspension and 2. 6in tires mean that it makes us just as happy while earning our laps on climbs.