Could it be Raising Arizona, the 1987 black comedy by the Coen brothers, starring Nicholas Cage and Holly Hunter as a childless couple (he is a jailbird, she is a police officer) who kidnap a baby? They lose this child to a pair of ex-cons and the rest of the movie is a series of chase sequences involving the couple, the ex-cons and a well-armed crazy biker. There is no biker gang, just the lone biker who looks like he stepped out of a Mad Max movie and there is a scene involving the baby sitting in a car seat in the middle of the highway as the biker comes thundering down the road, all very Mad Max. There are clips on YouTube, one shows Nick Cage dreaming about coming of the biker - https://www.youtube.com/watch?v=CQ67ZyZtKjU&spfreload=10
Failing that, any of the Mad Max movies might fit.