Tailgating isn’t just for tailgates anymore.

What used to be a simple pre-game picnic lunch served out of the back of a pickup truck or station wagon has become a multibillion-dollar business that, to some fans, is more important than the game itself.

Few people know that better than Jeff Campbell, owner of Gameday Customs of Long Beach, Calif. Campbell outfits trailers designed specifically for the care and feeding of game-day tailgaters.

Small enough to fit in a garage or a recreational vehicle spot in a stadium parking lot, Campbell’s trailers cost from $13,900 to $18,500 and can be equipped with a wet bar, flat screen TV and satellite dish, a “kegerator” for keeping beer cool and a 1,000-watt generator.

There is even a toilet to accommodate frequent visitors to the kegerator.

It’s a business Campbell, 56, learned the hard way. In the 1970s, his family owned Sportland Trailer Sales and RV, a recreational vehicle company that boasted sales outlets in Long Beach and El Monte in California and Arizona. It had a manufacturing plant in Paramount, Calif.

Campbell joined the family business after graduating from the University of Southern California in 1974, just in time for the first oil shock to send the RV industry into a nose dive. The company soldiered on for a few years, but the second oil crisis in 1979 finished it off.

“It was tough to sell RVs when gas lines were going around the block and interest rates were at 20 percent,” Campbell said. “Timing’s everything, and we had none.”

Launched on a shoestring in December 2005, Gameday hit the market amid a boom in tailgating.

Claiming 50 million practitioners, the tailgating industry has its own trade association, a magazine and a convention that drew 25,000 people to Las Vegas in 2006. Membership in the American Tailgater Association, founded just three years ago, already has reached 150,000, said Kevin Miller, publisher of Tailgater magazine.

“Tailgating is so huge that some people go to the stadium just to tailgate and not even to go to the game,” said Darryl Dunn, general manager of the Rose Bowl in Pasadena, Calif.

He estimates that 10,000 people who “attended” last year’s USC-University of California, Los Angeles game never made it inside the stadium. It’s gotten to the point that the Rose Bowl might try to limit tailgating by non-gamegoers to lessen traffic problems and ensure enough parking for ticket holders, Dunn said.

Tailgating is most popular at college and pro football games and NASCAR races, although Jimmy Buffett concerts – which attract legions of dedicated “parrotheads” – also draw tailgating crowds, Miller said.

The reasons for the explosive growth are hard to pin down. Miller and others speak of the shared passion for a sports team or stock-car driver and the camaraderie of sharing a beer and smoked brisket with friends and fellow fans before an event.

Whatever the reason, the advent of advanced tailgating equipment like Campbell’s trailers has definitely amped up the experience.

“Ten years ago, we were sitting in the parking lot in my Volkswagen van with a bag of chips and a fifth of vodka,” said Kevin Anderson, 42, of Huntington Beach, Calif., who went in with his brother-in-law in March on a $17,000 Gameday trailer. “Now, we have 40 to 75 people at our tailgate.”

Anderson, a 1986 USC graduate, even gave Campbell an impromptu radio plug when he mentioned the company’s products during an interview with a local sports talk radio station before November’s USC-UCLA game, where he was tailgating outside Los Angeles Memorial Coliseum.

Campbell said he expected to sell 22 trailers this year (about $400,000 in sales) and hoped to increase that to 30 to 40 next year. After a slow start, he said, he’s now turning a profit – a nice trick for a 2-year-old business.

The idea for Gameday Customs came while he and a friend were tailgating before the USC-California game four years ago. A guy with a beat-up old trailer outfitted with a grill and a satellite dish inspired Campbell’s friend to suggest that they build their own.

The first trailer was intended to be their personal party wagon. But the reaction from the tailgating community hinted at bigger things.

“We took it to the SC games and the response was so positive we thought that maybe this was a viable business,” Campbell said.

Using $50,000 of his own money – all but cracking his nest egg – Campbell set up shop in rented industrial space in Long Beach. He bought several stripped-down two-wheeled trailers from an Arizona outfit called Wells Cargo and gave them the full Gameday treatment.

That was mistake No. 1.

Turns out not everyone needs to keep a keg cold, so for some early customers, he had to pull out the kegerator and install a mini-refrigerator instead. Or maybe they wanted a bigger TV or more powerful generator.

Campbell now installs just the basic interior fittings and wiring in the trailers, adding the big screen TV, satellite dish and other extras only after he has a customer’s order in hand.

He also had trouble figuring out a workable marketing scheme. An ad in the local newspaper didn’t generate any responses and he couldn’t afford radio or TV commercials. The $2,500 he spent on a Web site (www.gamedaycustoms.com) wasn’t scaring up business either.

So Campbell started hauling the trailer to games at the Coliseum and the Rose Bowl, indulging his love for USC football while getting exposure for his product. Orders started trickling in, word of mouth led to more sales and customers finally began finding him in cyberspace – leading to orders from Seattle, Texas, North Carolina and other locales.

Working alone, Campbell takes about two weeks to complete a custom trailer, but with his current order backlog, a trailer ordered today will take four to six weeks for delivery. He recently hired his first employee to speed up production and to relieve him from 55-hour workweeks. That doesn’t count game-day sales time – he was in the Coliseum parking lot at 5:30 a.m. for the USC-UCLA game – which he considers more fun than work.

Campbell’s goal is to build the company for five years and then sell it to someone with deeper pockets who can finance a more ambitious expansion plan. In the meantime, he’s cooking up ways to reach his core tailgater customer base while steering clear of markets where he would get sacked by bigger RV players – such as toy haulers or camping trailers.

And he’ll keep doing the kind of personal market research that comes naturally to a tailgater.

“Unlike a lot of guys, I actually use my product,” said Campbell, who’s pictured on the Gameday Web site in full tailgate mode, beer cup in hand. “I know what works through personal experience.”

AP-NY-12-26-07 1315EST