Wheel Science: Two Can Be More Fun Than Four

$645, from Montague (www.montagueco.com [1]) or through bike shops.

Credit: www.montagueco.com

The bicycle would seem to be a good argument for intelligent design. Simple but ingenious -- the few essential parts are a handlebar, two wheels, pedals, and a chain on two small discs to convert human energy into forward motion -- the bike seems like something that has always been around, always pretty much the same. But, in fact, the bicycle makes a convincing case for evolution. In its dinosaur period, its front wheel was enormous, its rear wheel a tiny, spinning afterthought. The rider had to mount from a stool, and in those helmetless days, a fall from the bike's great height could be calamitous.

To become the lightweight, multigeared, fast and friendly creature we know today, countless mutations took place, and some iterations turned out to be more fit than others. And so it goes today, with variations on the two-wheeled theme constantly appearing, facing the competitive jungle, and surviving -- or not. Here, with our hope for their success, are two new bikes on the evolutionary ladder -- and one lovable brontosaurus.

$279, from Design Within Reach (www.dwr.com [2])

Credit: www.dwr.com

Paratrooper
The Pentagon has given us the latest in collapsible bicycles. Made by the Montague Corporation, in Cambridge, Massachusetts, the Paratrooper was designed to be carried by U.S. Army Special Forces troops as they jump out of airplanes into the boonies and the badlands. The rugged mountain bike, featuring a hardened aluminum frame, weighs 29 pounds and folds in less than thirty seconds into a package 3 feet by 3 feet by 1 foot. Very useful, apparently, in Afghanistan, and just as handy for Stan and Jennifer in their SUV -- no parachute required.

LIKEaBIKE
Never mind the trikes and the training wheels. For kids ages 2-5, this sturdy little wooden pedal-free mini lets its rider use his or her feet to roll along, so learning the art of balance is a natural process that takes place at a child's rate. As designer Rolf Mertens puts it, "Your child can make independent progress without adult help, using just their innate ability and coordination." Solidly constructed of birch and stainless steel, with a nicely padded cotton seat and wheels of alloy and rubber, the bike is more expensive than a hollow-plastic Big Wheel, but it has the toughness to work for more than one generation.

$230, from Schwinn (www.schwinnbikes.com [3]) or retail stores.

Credit: www.schwinnbikes.com

Schwinn Cruiser SS
Sometimes evolutionary dead ends aren't dead at all. Sure, the T-rex is pretty much passé, and the duckbilled platypus is just too weird, but for sheer comfort on a nice noncompetitive Sunday ride, there's nothing like this classic fat-tire bike, first designed in 1955. Okay, it's almost stubbornly retro, but with its whitewall tires, sculptural frame, sprung seat, coaster brakes, and cool old-style chain guard, the SS is one legacy of the Eisenhower era well worth reconnecting with.