By STEPHEN REGENOLD

Over the course of two dark winter evenings, working alone in his basement at a makeshift sawhorse stand, Jay “Hollywood” Henderson carefully drilled 600 tiny holes in his bike tires. “At least 600, maybe more,” he said.

Then, using a method he will describe only as his “ancient Chinese secret,” Henderson inserted hundreds of sheetmetal screws from the inside of the tires out, creating a pair of rolling, slicing, cutting, biting wheels of death that are tailor-made for the sport of ice biking.

“If you don’t want to fall on your head, homemade tires are a must for this sport,” he said.

Henderson, a 35-year-old bike shop owner from Minneapolis, is an ice biking champion. His sport of choice — an amalgamated winter cycling discipline with a small local following — is practiced on the glaze surfaces of frozen lakes, rivers, and skating rinks across the continent.

Ice racers sprint on large looped courses often carved from a mantel of snow, pedaling fast on straightaways, and slowing to skid through turns. The sport, which takes cues from the studded-tire motorcycling popular on frozen lakes in the 1970s, mixes elements of dirt bike rallies with criterium road races, plus a dash of roller-derby on the side.

About a dozen ice-bike races take place each winter across the United States and Canada. The sport, a phenomenon only of the North, is big in Anchorage, Toronto, Winnipeg, Minneapolis, and Montreal.

Bike types vary in the sport, with mountain bikes dominating the race pack, some single-speed models skimmed down to just the bare racing essentials. Some people ride city bikes without metal studs on the tires, pedaling slow and smiling, treating the race as a strange midwinter festival, not a competition.

“Ice biking is a chance to get outdoors in the offseason, to blow off some steam,” said Chuck Hood a 36-year-old product manager at a bike-parts distribution company who helps organize the Chilly Chili Ice Race, held each January on the frozen surface of Bush Lake in Bloomington, Minn. “We get Tour de France wannabes, bike messengers, and people in costumes, but everyone is having fun.”

One year a racer rode in the Chilly Chili Ice Race in a full scuba suit — fins, mask, snorkel, and all.

For riders like Henderson, however, ice bike racing is serious competition. Prize money is nonexistent. But the thrill is in the race, where riders skim along on a glassy sheen, screeching and tearing through turns, jockeying for position, tires humming on the ice.

At the 2005 Chilly Chili Ice Race, Henderson was physically maxed after several laps around the course. “I puked three times then pedaled across the finish line to win,” he said, a tiny choke of pride in his voice. (Henderson won this year’s Chilly Chili Ice Race on January 28, his fourth overall victory in the series.)

All serious ice bikers employ tires with studs or spikes, which are commercially available from companies like WTB, Schwalbe and Kenda. Top riders like Henderson make their own.

To a point, equipment can trump athleticism in the sport, where the rider with the best traction has an immense advantage. Mass-produced studded bike tires, which are made primarily for commuting or riding snowy trails, can keep you upright, but they do little on the glassy turns of an ice-racing course.

Russell Loucks, a 45-year-old software engineer from Eagan, Minn., can attest: “I’ve rammed many snowbanks trying to make a turn with these tires,” Loucks said during a recent ice-bike training day on Brownie Lake in Minneapolis. Loucks’ studded tires, which are mass-produced commuters, work fine on snow, but they’re less stable on ice. “I just haven’t had the time or motivation to do what I need to do.”

What he needs to do, according to veteran ice racer Tim Norrie, is build his own custom ice tires. Norrie, a 31-year-old electrician from Minneapolis who won the 2006 Chilly Chili Ice Race and took second place in this year’s event, employs hundreds of sheet-metal screws like Henderson and other top racers. “They’re 3/8 inch, size No. 6 screws with a pan-head top,” Norrie said. “I buy them by the box at the hardware store.”

On the ice Norrie’s tires sear long perforated paths, audibly crunching and chewing the frozen blue. Screws poke from rubber knobs, and they’re sharp to the touch.

During a recent practice session, Norrie carried his bike from his parked car to the surface of the frozen lake. He set the bike down carefully in the snow beside the ice track before getting on, tire spikes glinting like diamonds in the sun. “These things touch nothing but ice,” he said.