Dax Shepard has a passion for two things: fiancee Kristen Bell and cars. So it made sense that the 37-year-old actor-writer-director combined both for his new action comedy film, Hit & Run, in which the couple co-star while spending most of the film being chased in his 1967 Lincoln Continental.
''I spent two years rebuilding that car,'' Shepard says of the sleek black vehicle also starring in the film. ''But the first time I took Kristen out for a ride in it after it was completed she said, 'You spent all that money to make it sound like it's breaking?'
''This is a woman who cares so little about cars, she drives an electric car, so she's been very patient with my hobby!''
Hit & Run is the story of Charlie Bronson (Shepard), a nice guy with a questionable past who busts out of witness protection to deliver his fiancee (Bell) to Los Angeles for a once-in-a-lifetime job opportunity. Their road trip becomes dangerous when the gangster he put in jail (Bradley Cooper) finds out where he is and goes after him, trailed by the hapless federal agent supposed to be protecting him (Tom Arnold).
Bell, his 32-year-old partner of five years, is best known for the TV series Veronica Mars and films including Forgetting Sarah Marshall and Couples Retreat.
''Every actor in the movie, the role was written specifically for them,'' Shepard says. ''The goal of this movie wasn't to crack the secret recipe of what would be successful but was all about getting together with friends and people we trusted and working together for the sake of working together.''
Shepard grew up in Detroit with cars in his blood. ''I think all males from Detroit have an obsession with cars,'' he smiles. ''My stepdad was an engineer in the Corvette group at General Motors, my dad sold cars and my mother owned a company that did all the press functions for GM, so I started working for GM at racetracks when I was 14 and then worked for their race team until I moved to LA to go to college.''
After graduating from UCLA with a degree in anthropology, Shepard joined the Groundlings comedy troupe and tried to become an actor.
''I couldn't even get a theatrical agent and eight years went by until my first real job,'' he confides.
''I drank and did a lot of drugs, which was a reaction, I think, to how hopeless it was at times. I would stay sober for a job and then get drunk and use in between, but after I got sober for … Zathura  and got my shit together, I never went back.''
Shepard is surprisingly open and funny about his chequered past and admits much of the banter in the film with Bell was inspired by their differences.
''What I love about Kristen is she's the opposite of me,'' he says. ''When I meet a man on the street, my first thought is, 'This guy is going to try to mug us,' and her first thought is, 'I bet this guy is going to cure cancer tomorrow,' and neither of us is right but if you put us together we're getting closer to the truth.''
After Zathura, Shepard continued working on the hit TV prank show Punk'd, but stumbled through a string of flop big-screen comedies including Idiocracy, Let's Go to Prison and The Comebacks.
''I was trying to become Will Ferrell or some huge comedic franchise, because I thought that's what you should aim for,'' he says.
''In being that calculated, I set myself up for failure so I finally regrouped and ended up on TV in Parenthood because I'd been hired as a writer by the company that made the show and they offered me an acting job.''
After three years of playing Crosby, the commitment-phobic brother on hit drama Parenthood, Shepard admits his career is still a work in progress.
''I realise that the second I stopped trying to steer the outcome of all these things I was involved with, the better the results have gotten,'' he says.
''I've learnt that I've had the best results from just trying to be me, trying to make a movie or TV show I want to see or write a script I want to read, and that's really all I can offer - being authentic.''
Dax Shepard's top car flicks
Smokey and the Bandit (1977)
Burt Reynolds as the Bandit is hired to run a trailer full of beer over county lines. "That was the movie that started it all for me as a kid because it was equally funny and has very kick-ass car driving."
Burt Reynolds plays an ageing stuntman forced to come up with better moves to stay in the game. "Hal Needham directed all three of my top car films of all time; he was a legend."
Steve McQueen stars as a cop determined to find the man who killed a witness under his protection. "Bullitt has to be on every single list of great car movies of all time because nobody does it better than Steve McQueen."
Cannonball Run (1981)
Burt Reynolds stars in the film about an illegal cross-country car race. "These movies have this magical thing where they are clearly friends having an amazing time and it makes you want to be a part of it."
The film about a motorist terrorised by a truck was one of Steven Spielberg's first films. "Spielberg got some epic shots in that movie and I watched it before we did our movie, although I didn't steal any shots, if he asks!"
HIT & RUN
GENRE Action comedy.
CRITICAL BUZZ This low-budget chase movie is hyped as a sleeper hit in the US.
STARS Dax Shepard, Kristen Bell, Bradley Cooper, Tom Arnold.
DIRECTORS Dax Shepard and David Palmer.