The folding bike is riding the cycling commuter wave, and the clever engineering is making it quicker than ever to carry on a subway or in a car trunk. Now found in some regular bike shops as well as specialty urban-transportation stores, better designs are helping the bikes shrug off a nerdy-professor stereotype of being ugly, tiny-wheeled, poor-riding machines. Breakthrough models come with chainless belt drives, electric engines and even recumbent formats. Most sport 20-inch wheels to make the bikes compact when folded, with elegant frames that hinge and lock at mid-frame. That keeps the drive-train area (front chain rings to rear wheel) intact and makes the bikes so solid that you almost forget that they fold up.
Tern Eclipse X20: The sleek-looking, slickly designed 20-speed folder has a convenient N fold and 24-inch wheels, which are 17% bigger than the 20-inch standard of folding bikes.
Likes: A superb ride. It has the best of both worlds: a compact fold-up bike with a "big-bike" ride, due to wheels just 2 inches shorter than those of a mountain bike. In particular, it holds momentum better and is less twitchy in slower-speed handling than the 20-inch-wheeled bikes. Yet it folds up almost as small, with a unique N-fold design that hinges at mid-frame and sets the wheels side by side in parallel, held together by a magnet. It can be pushed forward like a baby stroller and left free-standing. The frame allows for wider mountain bike-style tires. The handlebars fold down too and are neatly held in place by an integrated rubber clasp. A family of models with the same frame starts with the Node D8 8-speed ($750).
Price: $2,200; http://www.ternbicycles.com
A2B Kuo Electric fold-up: The market's only folding electric bike is a seven-speed with 20-inch wheels, a 250-watt motor, 24-volt lithium-ion battery, an unassisted top speed of 15.5 miles and a range of as many as 25 miles, based on rider weight.
Likes: The Kuo is quite inexpensive for an electric bike and folds up small, making it a great train-bike commuting solution. It takes no more than a minute to fold; the pedals flip up, and the mid-frame and the gooseneck stem pivot to put the wheels side by side, allowing you to walk it like a stroller. A handlebar LED display includes speed, distance and battery charge. Tested weight of 44 pounds is low for an electric bike. It plugs into a wall outlet for recharging and rides like a regular bike with the motor switched off. A bell, light and kickstand are included.
Price: $1,399; http://www.wearea2b.com/us
Bike Friday Silk Alfine 11: One of the first folders with a belt drive instead of a standard metal link chain, it includes 20-inch wheels, disc brakes and an 11-speed internal hub. The Silk can be bought alone or as part of a dedicated travel system that fits into, and can also pull, a Samsonite luggage case.
Likes: Solid, fast, quiet, maintenance-free ride. No chain and external gears to oil. The bar-end handlebars provide superb leverage during out-of-the-saddle hill climbing. The belt-drive is smooth, and it's silent as midnight. The stock bike folds up in about five seconds; a single uncoupling at the juncture of the seat tube and main tube tilts the seat forward and lets you pull up at the center and draw the front wheel backward toward the rear wheel, forming a vertical A shape that you can roll forward. It is not as elegant as the Tern's fold, and the front wheel can still pivot, but it'll still get into tight places.
Dislikes: You can shrink the folded Silk more by detaching the quick-release handlebar/stem in about two seconds with a turn of a lever, but that's more of a hassle. The bike should come with a folding stem (optional) or a way to clip the bars/stem in place on the frame.
Price: $1,998; $2,459 with a rack and the Samsonite suitcase/trailer conversion; http://www.bikefriday.com
Lay back and fly
Azub Origami: This sleek, Czech-made, 24-speed is the market's only folding two-wheel recumbent. It has 20-inch wheels, a built-in rack and a kickstand.
Likes: Speedy and comfortable, with none of the neck or back strain of a normal upright bike. That's due to lay-back recumbent position and Tyrannosaurus-rex hand placement. (You can ask the dealer to put on wider handlebars, which I would have preferred.) For variety, the handlebars can be pushed forward as you ride. The seat adjusts 5 inches up and down. When you're done, the handlebars fold down and lash to the top tube while the wheels fold to parallel, making it easy to wheel into a closet or a subway car. The burly, two-sided motorcycle-style kickstand is rock solid. A large under-seat cargo bag is available ($129).
Dislikes: No water bottle mounts; you'd have to mount one on the stem. Takes about a minute to fold, which is much longer than the others because you have to detach the seat.
Price: $2,190. http://www.azub.eu
Wallack is the coauthor of "Bike for Life: How to Ride to 100." firstname.lastname@example.org