The last big breakthrough in mountain biking was the creation of 29-inch wheels – bikes equipped with them, while slow and unwieldy, could pancake everything in their path, and made newer riders confident enough to saddle up and take on steep, rocky downhills. Now there's a new sweet spot: the 27.5-inch wheel. These have plenty of leverage over roots and rocks, but are lighter and have a shorter wheelbase than 29-ers. This means riders can be more playful with them, and so can mountain-bike manufacturers, who are changing geometry to accommodate nimbler, easier training. We pedaled hard to find the best of this new breed.
The Hardcore Trail-Buster: Yeti Arc Carbon Enduro
The mass of this bike's frame sits insanely low in the cockpit, around your shins, for BMX-quick handling. Our test model weighed slightly more than 23 pounds, thus making short work of uphills. And thanks to a supertight wheelbase, cornering is instantaneous – but be warned: You can overcook curves if you're not on your game. That right-now reaction time is the result of an ultrastiff, unforgiving carbon chassis, so while you'll blow past other riders in mud and rough terrain, your spine will feel the lack of rear suspension. [$3,400; yeticycles.com]