WHEN MOST MOUNTAIN BIKES are stacked with 27 gears, why are so many cyclists turning to single-speeds? Easy: They're light and simple, fun to ride, and whip you into a better, stronger cyclist. Granted, you may break a serious sweat on rides that were previously cake on your geared bike. But that's the point: There's a raw pleasure in testing your limitsand using just one little gear to burn off your buddy on his overstuffed mountain hog.
MOOTS UNO YBB / $5,100, 21 lbs
Why It's Cool: This ridiculously lightweight titanium ride will win over the staunchest single-speed skeptics.
The Ride: The Uno is nearly as svelte as a road bike, making the midrange 36x16 gearing easier to push on climbs than the competition. The hand-built ti frame is stiff and smooth, with clean welds NASA would envy. The YBB softtail takes the edge off the rough stuff and keeps the rear wheel connected to the dirt on ascents, meaning you stay in the saddle longer and conserve precious energy. Downhill, the Uno excels on tight, swoopy, banked singletrack. The stable-platform Fox F80X fork damps three inches on rocky descents but goes rigid when the trail turns smooth. And the disc-brake-ready slider dropout makes it easy to tension the chain. It also lets you sub in a derailleur-compatible hanger in case you ever lose the single-speed mojo, making this frame a lifelong investment.
Right Bike If: You're already a single-speed convert and you want the finest ride available. Sizes: custom and 12, 14, 16, 17, 18 (tested), 19, 20.5, and 22 in; www.moots.com