Venice Beach, pre-gentrification: The sun is setting on the golden age of surfing, and the generation of young Americans born in the 1960s rides its final waves as they break against a crumbling pier. On land, these young punks in tube socks cruise the grimy asphalt on wooden boards rigged with hard, plastic wheels, thrilling to their own kinesis and bad attitude. Multiethnic and working class, utterly apolitical and totally disaffected, they are the spiritual predecessors of the hip-hop movement to come, appropriating dead-end urban space for the performance of outlaw self-expression.

Suddenly, a new technology appears: responsive urethane wheels. The paradigm shifts; a subculture explodes. The Z-Boys of Dogtown, as they are called, literally go wild in the streets. (Because of a drought, they also stake their claim on the empty swimming pools of the middle class.) At the epicenter of all this activity is the Zephyr surf shop, run by a benevolent counterculture burnout. This being the 1970s, he quickly calculates the earning potential of his whippersnapper collective and their highly marketable new toy.

With the help of cunning graphic designers and hip photographers, the Z-Boys are branded and sent out to conquer the skate-tournament circuit. The manufacture of Zephyr Skateboards goes into overdrive. There is fame, fortune, and fabulous fashion. Egos clash. Groupies swarm. Rival entrepreneurs rattle the Dogtown solidarity. One Z-Boy lands in jail on drug charges. Another is diagnosed with brain cancer. And one of them, Stacy Peralta, grows up to make an exuberant documentary about their whole crazy story.

That film was called “Dogtown and Z-Boys.” It won two prizes at the 2001 Sundance Film Festival, and a rave review from this critic when it opened the following year. Bursting with oversized personalities, jaw-dropping athleticism, and potent sociocultural significance, the birth of skateboarding was a perfect story, and Mr. Peralta told it just about perfectly.

Now, alas, he has told it again in “Lords of Dogtown,” a dramatization of the Z-Boys saga based on his screenplay. Catherine Hardwicke (“Thirteen”) is the director, and the cast includes Victor Rasuk (Tony Alva), the promising young actor from “Raising Victor Vargas”; John Robinson (Stacy Peralta), the pink-cheeked kid from “Elephant”; Johnny Knoxville (Topper Burks) as a pimped-out promoter, and Heath Ledger doing a remarkable Val Kilmer impersonation as Skip Engblom, proprietor of the Zephyr.

Why is the drama so much less dramatic than the documentary? Part of the problem is the attempt to flesh out the human interest. A story that comes on this fast and furious has little time for cliched psychodrama. Familial conflicts pop up like screenplay ideas to be filled in at a later date – or in another movie. Romantic entanglements give a pretext for saucy teen grope fests, but Ms. Hardwicke is oddly indifferent to her female players.

It may also be that there’s too much going on; the story is too perfect. In a strictly factual telling, the tidal wave of detail swells with its own natural momentum. Fictionalized, it’s almost ridiculously overstuffed. (No one making this up would dare the braincancer coda.) To her credit, Ms. Hardwiche wastes little time on exposition. For the most part, she barrels through the material; her key directorial move is to launch her camera at the action and let it smash, tumble, and roll along with her hyperkinetic heroes.

Less appealing is the ersatz 1970s movie aesthetic. Attention, indie directors: Gritty, low-light lensing and rough, handheld camerawork does not equal authenticity. And it’s downright amazing how little energy is tapped from the wall-to-wall pop soundtrack. No one is to blame, however, for one of the picture’s greatest shortcomings. Eager as the young actors and their stunt doubles are, you can’t come close to duplicating the grace and verve of that original skating.

This would hardly matter if every last move of the Z-Boys hadn’t been so extensively documented back in the day, and so joyfully exhibited throughout “Dogtown and Z-Boys.” If you haven’t seen the documentary, you’re sure to find its fictional remake more enjoyable than I did. But why bother? If you haven’t seen the documentary, see it.