You may notice a new sound in the aluminum armada of this year's bicycle season: the steady hum of an electric motor.

Electric bicycles are zooming around the U.S. these days, and may well be the biggest new thing on two wheels.

"Electric bikes offer comfort and convenience, but you're still pedaling so you can enjoy the experience," said Ann Hanson, vice president for electric-bike maker THINK Mobility. "It's not like a moped, which is a passive experience."

Think Lance Armstrong minus half the sweat. Would-be master cyclists who find themselves struggling up a daunting incline can use the electric motor to propel them over the hump and leave frustrated competitors eating ozone.

Sales of electric bikes in the U.S. have jumped from 1,000 to over 30,000 a year since 1995. In gizmo-loving Japan, there are an astounding estimated one million battery-powered two-wheelers, Hanson said.

Pride and Prejudice

Many cyclists tend to dismiss bells-and-whistles vehicles that stray from the streamlined purity of the traditional speedster. With its 24-volt battery that charges in a wall socket overnight, its light-up indicators, motorcycle-like rev grip and Jetsons-esque look, the THINK bikes, are slightly gauche for purists.

J.P. Partland, a freelance writer, cycling expert and contributing editor at The Ride, said electric bikes bring up troubling issues for bicycle enthusiasts who want get American feet to let up on the gas pedal and bear down on the bike pedal.

"I don't know if it's elitism, but a lot of people who are involved in cycling as a transportation believe that anything that makes cycling seem carlike is frowned upon because it makes biking seem like a marginal activity," he said. "With an electric bike, you can get someplace marginally faster, but people should sweat a little.

Hanson admits some experienced bikers "glare when they see that fellow who sails by on an electric bike." But she also knows others who are all for biking of any sort.

"I had a friend who's a hardcore bicyclist, and the first time she tried this, she had such a good time," she said.  "She said ... if an electric bike is what it takes to get someone who otherwise wouldn't ride to get out there and have some fun, then she was all for it."

Putting on the Pounds

But then there's the bike's weight. THINK Mobility is the electric-vehicles subsidiary of Ford Motors, and that ancestry shows with the tank-like frame of the their Fun bike: 70 pounds of aluminum that feels twice as heavy when you're wrestling with one on a flight of stairs in a city brownstone. While the motor helps conquer hills, the extra weight can drag a rider down if the electric assist malfunctions.

Oh, and it has all the maneuverability of a Winnebago.

"This would be kind of hard to pedal even on a level surface if you didn't have the motor," said John Falls, 36, a New York photographer experimenting with the Fun in a Brooklyn park last week. His own bicycle weighs under 20 pounds.

It's also not a fun thing to get your leg trapped under, as one admittedly clumsy rider found after skidding out on a wet street.

Weight's not as much of a problem with the Traveler, the smaller model, which has been placed on In-Style magazine's Hot List and ridden by Matt Lauer on the Today show. At 40 pounds, minus the 13-pound battery, the bike can be folded to fit into the trunk of a car. The trade-off comes in the distance it can be ridden and its top speed, only 16 miles and 18 miles per hour, respectively to the Fun's 22 miles and 20 miles per hour. Both are priced at $995.

In either case, the bikes aren't cross-country road-trip material, but it does get some otherwise sedentary sorts out and about. Besides commuters who are not in the best shape, and bike enthusiasts who love gadgets, electric bikes are meant to put bicycling back its place in American culture, Hanson said.

"Bikes are a real rite of passage," she said. "It's your first taste of freedom."