N.Y, N.Y.: This could be the toughest bike town : Thieves prey on bicycle owners. Then there’s tortuous traffic, kamikaze cabbies, door-opening motorists.

Shift gears but pedal fast. New York may be the toughest bike town in America.

How tough?

The Kryptonite Corp., a bicycle lockmaker, will pay up to $1,000 to an owner whose bicycle is stolen anywhere in the world if the company’s ultrastrong lock is broken--except in Manhattan.

Rings of bike thieves here are just too skilled, sometimes employing battery-operated power tools and industrial-strength diamond blades.

When Kryptonite found that 80% of the claims on its offer came from Manhattan, and that it was paying hundreds of thousands of dollars, it canceled its commitment.

“Rather than having to take on criminals, we dropped our guarantee,” said Liz Zane, a company spokeswoman. “In a lot of cases, we have found bike theft can be traced back to the drug problem. You are not just talking about an 18-year-old kid who is after a bike.”

“New York is the bike theft capital of North America,” said Jon Orcutt, executive director of Transportation Alternatives, an organization promoting bicycling in New York City. “You don’t want to leave your bike out in Midtown Manhattan.”

John F. Kennedy Jr., , who works as an assistant district attorney, had his locked bicycle stolen last year. So did actor Matthew Broderick, who now rides a beat-up decoy bike and locks and leaves it only next to more expensive models, hoping thieves will think upscale.

“I don’t want to make a big deal about it,” Kennedy said after he was robbed.

But it is a big deal. Police in New York reported 4,658 bikes stolen in 1992--and Orcutt, reflecting the views of other bikers, estimates that only one theft in 10 is reported to police.

Cyclists say that--considering the thefts, the city’s tortuous traffic, kamikaze cabbies and motorists who open car doors in Cyclists’ faces--it is clear that New York is indeed a very tough track.

Many bike riders tell of being struck by motorists--not once but multiple times.

“It’s tough for a cyclist to ride in traffic. Cab drivers are the meanest. They don’t look out for cyclists enough. I have been hit three times. I have had a lot of near misses,” said Robin Bailey, a former messenger who now works in a bike shop.

“I have been doored. The passenger opened the door and the door clipped my handle bars. I lost control. It threw me in front of a van and the van hit me. The van wasn’t going too fast. I had back pains. I went to a chiropractor three times a week.

“My last accident? A driver rear-ended me. He said:, ‘Are you OK?’ I said: ‘Not really.’ He started yelling at me and saying that it was my fault. We got into a fight and the cops came. It is the toughest bike town in the world.”

Added Sidney Filson, a free-lance writer: “If it’s not the crooks, it’s the cabbies and the buses. Buses ride close to the curb where bikers are, jamming them between parked cars and the bus. Cab drivers like to run you over. They cut in front of you and their passengers open the doors, making a nice solid surface for you to crash into.”

Tales of multiple bike thefts abound.

“I had three bikes stolen,” Filson said. “There is an arms race between the bikers and the thieves.”

In an effort to win the arms race, Kryptonite has equipped a laboratory with a special destruction machine that attacks locks with hacksaws, bolt cutters, pry bars, drills, hammers and just plain pulling.

“We can run products through the fiercest street conditions,” Zane said. “ . . . We have been struggling to come up with something that will be clever enough and strong enough to outwit these clever thieves in Manhattan.”

And after extensive testing, Kryptonite thinks it has finally found the answer. The company plans to introduce a new extra-strength lock, reinstating its $1,000 guarantee against theft in Manhattan later this year. This lock not only is designed to foil the fiercest pickers but is constructed of heavy gauge steel so that it can’t be leveraged open even by a car jack.

“As the thieves get better at what they do, we have to get better too,” Zane said.

Despite all the hardships, many New Yorkers remain enthusiastic cyclists. They point to the satisfaction and convenience of traversing the city under their own power, riding amid the greenery of Central Park, socializing with other bikers.

“It’s a sort of Dickensian situation,” Orcutt said. “It is the best of places to bike and the worst of places.”