ANALYSIS : Beach Boys’ Endless Summer of Schlock Concerts : Their performances are tired, predictable and dated. Nostalgia is the only reason the ‘boys’ continue to draw spectators.

The first trickle of what soon would become a deluge of vehicles had begun filing into the Pacific Amphitheatre parking lot early Sunday evening. Still more than an hour before a scheduled 7:30 show, several dozen people had gathered around a canopy pitched near a gaggle of parked cars at the back of the lot.

The crowd--ranging from teen-agers to middle-aged parents and even grandparents--swilled beer, joked and talked excitedly with a visitor about their beloved band for whom they throw a massive tailgate bash every year to greet the group’s arrival in town: the Beach Boys.

Why?

Why, indeed? After all, this is 1990, and the Beach Boys’ summer ended somewhere in the early ‘70s, didn’t it?

Yes, the Beach Boys may have been Southern California’s quintessential rock group, and certainly have etched a monumental fissure onto the face of pop music and all that. But with Dennis Wilson eight years dead, Brian Wilson often missing in action (as was the case Sunday), and the others often-pathetic caricatures of their former selves, they have long since become the Beached Boys and for years have been living this endless bummer of nostalgia tours.

Some less ardent fans, and a few knowledgeable die-hards, won’t admit it. Others, however, concede that the geezers they’ll see on stage tonight can hardly get away with calling themselves boys , and probably don’t spend much time at the beach any more (not that any of them but Dennis ever did), for risk of exposing their aging torsos to the beautiful girls about whom they sing.

Mike McAllister, one of the parking-lot party people, acknowledges that “they sound pretty bad nowadays.” But, he adds, “who cares? They still play rock ‘n’ roll, and we all love to see ‘em.”

That’s the weird part. There were plenty of nostalgia-mongers who loved the Who and Rolling Stones shows last year, but they believed, rightly or wrongly, that the bands still played great.

But the Beach Boys, even on a night on which their most loyal fans will admit they’re off, consistently and overwhelmingly please the multitudes.

“The truth is, it doesn’t matter what they sound like,” said Mick Carolan of Garden Grove, who estimates that he’s seen 50 Beach Boys concerts. “They could sound like hell, and these people would still come out--and keep coming out--to see them.”

Carolan said he has organized Beach Boys tailgate fests such as this one, attracting as many as 100 people, every time the group has played the Pacific Amphitheatre. And he plans to continue as long as the Beach Boys perform.

“The Beach Boys are an institution of American popular music,” he said. “They’re what started the rock music scene in Southern California. That California spirit is still alive, and it will never die. And that says it all.”

Actually, there’s more.

Call it the good, squeaky-clean fun factor. Regardless of what the group members were up to in their private lives, or what Brian Wilson may have intended in his work, Beach Boys music has always been perceived by the masses as simple, wholesome and happy ditties celebrating surfing, beach girls and good times in sunny California.

Inoffensive rock ‘n’ roll. Not like the Stones or what the Beatles became. The antithesis of punk or hard rap. The Beach Boys played music to which good girls and nice guys listened and danced.

“You could take them home to your parents, and your parents didn’t mind you picking up on the fads they started,” said Chuck Williams of Santa Barbara, self-proclaimed No. 1 Beach Boys fan and authority on the band. “Sure, the guys may have experimented with drugs at one time, but they always kept that out of their music. So parents accepted them.”

Consequently, they project the image of the perfect band for the whole family. Tipper Gore never attempted to censor a Beach Boys song, and Reagan Administration Secretary of the Interior James Watt surely remembers what happened when he tried to ban them from playing at the White House and raised the ire of Beach Boys fan Nancy Reagan in 1983. They’re nice, G-rated family entertainment.

While that says nothing about the Beach Boys’ relevance in contemporary pop music, it does make them a singular nostalgia rock act. Toddlers as well as blue-haired grandmothers, and scores of others in between, all love a Beach Boys concert. Entire families, covering three generations in some cases, enjoy the spectacle, however contrived, calculated and manipulative it may have become.

Give or take a song or two, you always know what to expect at a Beach Boys concert (except whether or not Brian will show), and Sunday’s show provided case-in-point: The medley of car songs, the big surfing songs and other classic hits, performed much the same way from one show to the next, and complete with such stilted show-biz antics as choreographed young, bouncing bikini girls and phony onstage conversation.

The fans know it. But that’s what they’ve paid to see.

“Yeah, it’s predictable, but it’s not so bad. The crowd makes it all worthwhile,” said Phillip Yarbrough of Fullerton, who said he has attended every local Beach Boys concert since 1976. “It’s their spirit and enthusiasm. . . . The crowd is always upbeat. There are no drugs or no fights. It’s really positive.”

Williams, whose obsessive love for Beach Boys music immersed him in a longtime friendship with the band members, including a spell as Mike Love’s traveling press secretary, estimates that he has seen 80% of the band’s concerts. “Hundreds, at least. Maybe 1,000,” he said.

He acknowledges that it is rather disheartening to see “the Boys” today relying on many of the stage crutches on which they now lean heavily during performances, and he feels “a personal loss” when Brian Wilson doesn’t perform.

“But show biz is show biz,” he said. “Still, it’s incredible what they’re doing. I’ll always want to go see a Beach Boys show. The Beach Boys are fun to me. Sometimes, I’ll just stare out at the crowd. And it’s amazing. . . . People go to the show happy, and they leave the show happy.”

They know it’s only recycled rock ‘n’ roll. But they like it.