While doing nothing to dispel the stereotype that skateboarding is the sport of brainless jackasses, Casey La Scala's directing debut does feature some nifty boarding action. It is also, at 102 minutes, much longer than such a trifle needs to be. "Grinding," for those who don't know, involves scraping one or both axles on a curb or railing, thereby impressing the hell out of like-minded souls. The plot, to the degree to which it can be so characterized, involves four dopey, Chicago-based skateboarders who'd sell their grandmas to the circus for the opportunity to skate with Santa Monica, Calif., superstar Jimmy Wilson (Jason London). As the formula for this sort of ...