"Fuck. You. Motorcycles," Jon Hamm says in a low, grinning growl. The delivery is pure Don Draper, but the guy behind the wheel is looking a whole lot more laid-back in his madras shorts, Wayfarers, and beat-up St. Louis Cardinals cap than his tortured television alter ego ever does.

It's a sunny summer day in Malibu, the kind that makes any trip up the Pacific Coast Highway feel like a car commercial or a scene from a jubilant surf movie. Or that's how it would feel if this pack of leather-trousered bikers would kindly unclog the road. The moment there's an opening between the hogs, Hamm hits the accelerator and we take off, a silver blur hurtling toward Oxnard. The blur, in case you can't make it out, is a not-yet-released gullwing SLS AMG, on loan from the good folks at Mercedes-Benz.

This is, as Hamm notes, a "bizarrely lunatic car." It's insanely fast. "That was 140," he says calmly as he eases back down to a reasonable, autobahn-worthy pace. Hamm recently became the voice of Mercedes, lending his sonorous, all-comforting, all-promising pitchman's authority to its TV spots.

"It's funny, right? Kind of this weird synergy," Hamm says, alluding to the fact that the role he's most identified with—Don Draper, the powerful and powerfully conflicted master of advertising on AMC's Mad Men—has now led to an actual gig selling cars.

"It's strange, but it's good for me. I vote yes."

His lazy-Sunday strategy is to drive nowhere in particular, avoid any unwanted attention from the California Highway Patrol, maybe pick up some lunch. The plan is to not have much of a plan, which seems to suit Hamm just fine. The 39-year-old has a rare weekend off from shooting Season 4 of Mad Men. As a kind of in-town vacation, he and his longtime girlfriend, actress and screenwriter Jennifer Westfeldt, are borrowing a cottage right on the beach in Malibu.

When I showed up earlier in the day, their big dog, Cora, a shepherd mix, was happily lounging in the sand. Westfeldt was waiting on friends, and she and Hamm had plans to fire up the Big Green Egg. Sinatra was playing in the living room. Hamm and Westfeldt have an easygoing sweetness with each other that comes from being together a dozen years and getting off on the same stuff. They offered me a drink ("Budweiser—in a can, no less") and talked about a film they're producing this fall that Westfeldt wrote called Friends With Kids.

It would be easy to draw parallels between this borrowed California-dream life—the idyllic beach house and the exotic super-car, both on loan—and the feints and fictions of Don Draper's borrowed life. Unfortunately, that would be pretty much bullshit. Because unlike Draper, Hamm isn't a man from nowhere. For the past 15 years he's been living here in Los Angeles, piecing together his résumé, quietly building a career and a life. And if it's taken this long for him to enter the American consciousness as an archetype of homegrown masculinity, well, we probably have ourselves to blame. Every generation gets the heroes it deserves.

•••

"All the drifters eventually end up here in Southern California," Hamm says as we meander along the coastal highway. "I came out to visit with my mom when I was 9 years old and then again right after she died. I liked the cars, I liked the sun. I just thought, 'This is for me.'"

Hamm grew up in St Louis. His parents split when he was 2, and his mother raised him. Weekends were spent with his father, a larger-than-life character in the trucking industry who'd take him along to bars and clubs after work. Then, when Hamm was 10, everything unraveled horribly: His mother died of cancer. He was sent to live with his grandmother. His father died his sophomore year in college.

In school he played sports as much as he acted—but something kept drawing him back to performing. As he puts it, "I never minded standing up and looking like an idiot, which is tremendously helpful in this industry and not so much in others."