A dynamic glimpse of contemporary Los Angeles funneled into an old-fashioned coming-of-age saga, Lowriders isn’t always persuasive, but it has plenty of heart. Peruvian-born director Ricardo de Montreuil elicits strong performances for his first English-language feature, the story of a young graffiti artist, his ex-con brother and their old-school “Pops,” played with mournful reserve by Demian Bichir. The actors find the emotional weight in often overwritten material, but what sets the film apart is its deeply felt celebration of the lowrider tradition — the loving customization and display of vintage cars — that thrives in the predominantly...