Catherine Hardwicke demonstrated with “Thirteen” that she could create a raw, gritty California atmosphere and draw convincingly natural performances from young actors, and those skills serve her well in this dramatization of the early years of the “extreme skateboarding” phenomenon written by Stacy Peralta, who was a member of the first wave of the movement depicted here and who covered much of the same territory earlier in his documentary “Dogtown and Z-Boys.” The director’s edgy, motion-filled style suits the story of a bunch of precocious daredevils who, under the tutelage of a loopy surf-shop owner, revolutionized skating in the late seventies with their radical moves and take-no-prisoners recklessness. She also shows, once again, her aptitude in working with actors, drawing some striking performances not only from the young leads (as well as the stunt riders whose antics are perfectly meshed with theirs), but from most of the older cast members too–most notably Heath Ledger, who, as Skip Engblom, the proprietor of the Zephyr Surf Shop who hopes to make a bundle from his new boards and the explosive team he’s assembled to ride them to glory, is equipped with a set of false teeth even more pronounced than the ones Robin Williams sported in “The House of D” (indeed, they make him virtually unrecognizable) but puts them to far better use.

Where “Lords of Dogtown” stumbles is in the narrative. Quite simply, the movie works so long as it stays on wheels, but turns pretty flat-footed whenever it hits the ground, turning into a fairly typical tale of down-to-earth guys who sell out by succumbing to the lure of big bucks and losing touch with their roots in the process. The story starts in 1975, when a quartet of youngsters–skilled Peralta (John Robinson), Jay Adams (Emile Hirsch) and Tony Alva (Victor Rasuk) and wannabe Sid (Michael Angarano)–surf the dangerous waves that crash against the deserted Pacific Ocean Park pier on the coast near Venice, only to be ejected by the older riders. They’re also wild skateboarders who congregate at the surfing shop run by Engblom, a long-haired dude with glazed eyes and a drugged-out, dislocated manner who nonetheless recognizes the economic possibilities when a pal presents him with some special polyurethane skateboard tires that will allow riders to zoom up curbs and curved walls instead of moping along on level surfaces. He quickly assembles a team representing the shop (the Zephyrs, eventually called the Z-Boys)–one of the big crises here is that originally Peralta isn’t included, but eventually wins a place on the squad–and the boys’ maneuvers soon transform the whole sport (as well as encouraging them to look for ever-increasing thrills by breaking into private backyard pools to use the curved surfaces for their stunts). But the guys’ resultant celebrity inevitably leads to lucrative offers from bigger outfits than self-financed Skip can compete with, and ultimately both Tony and Stacy are unable to resist the lure of fame and fortune, with only Jay holding out against the siren corporate call. By the close he’s shaved his head and joined a local street gang, while Stacy remains fairly level-headed and Tony has to struggle with an injury that threatens his skating career. But despite their differences everybody’s brought together against when Sid’s struck by a terminal illness and there’s a last explosion of the old camaraderie in his honor.

In telling this story Hardwicke employs a large repertoire of camera tricks and technical devices to good effect, and with the aid of editor Nancy Richardson she keeps the skating action tight and invigorating. Her crew–production designer Chris Gorak, art director Seth Reed, set designer Scott Herbertson, set decorator Gene Serdena and costumer Cindy Evans–also prove proficient in visually capturing the place and period, and Elliot Davis’ cinematography gives the picture the gritty look the material demands. (The background score–lots of pop stuff supplemented by original music from Mark Mothersbaugh–is also effective.) The cast is admirable, too. Hirsch–with a string of interesting movies already under his belt– makes the biggest impression as the voluble, juiced-up Jay, but Rasuk (of the marvelous “Raising Victor Vargas”) and Robinson (of Gus Van Sant’s superb “Elephant”) aren’t far behind; and the nearly unrecognizable Ledger makes Engblom the very image of a stoned-out Fagin. Angarano has to play more for sentiment as the rather pathetic Sid, a goal which proves beyond his reach, and Johnny Knoxville is energetic but undisciplined as the snakelike Topper Burks, who persuades Alva to seek renown and riches. But even the best of the actors have trouble fleshing out their characters because context is lacking. We don’t see much of the home life of the skaters beyond Rebecca De Mornay’s spaced-out Philaine Adams and Julio Oscar Mechosi’s stern papa Alva; even Nikki Reed, who was so incisive in “Thirteen,” can’t do much with the part of Tony’s sister, whom Jay romances. (Nice-guy Peralta’s background is even sketchier, while rich-kid Sid’s is perfunctory and stoner Skip’s non-existent.) The result is that the figures we’re meant to sympathize with don’t possess the background that would give them dramatic heft. The social milieu that they represent is equally devoid of much content, which places the skaters’ rebelliousness in a vacuum–what, precisely are they rebelling against? And that in turn makes Jay’s “principled” stand against the sort of surrender represented by Stacy and Tony pretty empty. After all, when we get to the final reel, Adams’ choice is the culture of gang thuggery, which at best is nothing more than the corporate brutality his erstwhile buddies have gone into league with on a much smaller scale. The rebel is there, but the cause is lacking. And the weakness of this later section of the picture is accentuated by increasing clumsiness in simply telling the story. Even if the first two-thirds of the narrative aren’t terribly deep, Hardwicke manages to knit the various episodes together in a way that makes them cohere. In the final lap, though, the structure deteriorates, focus gets lost, and transitions get blurred; and the sentimental finale doesn’t quite gel. (The skating action is less frequent, too.) In short, the picture gets tired as it proceeds, rather like a rider in need of a rest. (It also suffers from the absence of Ledger, who pretty much disappears before a brief return near the close.)

“Lords of Dogtown” is thus very much like the sport it showcases: especially in the initial stages, it’s filled with flash, dash and exuberance and has a reckless energy that’s momentarily exciting. In the end, though, it’s rather simple-minded and emptily active, and runs out of gas. The verve of the first few reels may be impressive, but that’s all there is. So though as a technical exercise, the movie is impressive for a while, as a story it ultimately leaves a good deal to be desired.