The old-fashioned real-deal movie star charm of Will Smith can occasionally be glimpsed somewhere inside this overlong cacaphony of car chases, shoot-em-ups, and explosions. It is impossible not to watch him and almost impossible not to smile while doing so.

But that’s about the only smile in this generic but mind-numbingly loud and violent summer action movie, more theme park stunt spectacular than story.

Martin Lawrence and Smith reprise their roles from 1995′s “Bad Boys” as buddy cops who toss off wisecracks in between rounds of ammunition. They are cast against type with Martin as Marcus, the worrying family man and Smith as Mike, the go-for-it playa. This time, Marcus’ sister (played by the gorgeously talented Gabrielle Union), a DEA agent, is in town, but hasn’t told her brother that (1) she is working undercover on a dangerous investigation and (2) she is romantically involved with Mike. Meanwhile, Marcus and Mike have smashed up most of the cars in LA but have not yet made any progress on tracking down the drug dealer they are after. And many, many, many, many more cars will be smashed and many attempts at humor will crash before they do.

Director Michael Bay (“Armageddon” and “The Rock”) can shoot action sequences and stunts, though he tries a little too hard to be John Woo. He is less successful at making it worth caring about, especially when it veers into the truly preposterous with a massive invasion of Cuba at the end. For anyone other than hard-core action fans it just gets overwhelming and finally a little tedious. It also makes the fatal mistake of forgetting to include a memorable or interesting villain. Instead we get a stereotyped paranoid drug dealer who is overly attached to his mother and daughter.

Parents should know that the movie pushes the R rating to almost the NC-17 level with very graphic violence. At one point a truck filled with naked dead bodies is hit so that it opens up and spills the bodies all over the street, so that they are hit by other cars. The top of a corpse’s head comes off. A character is chopped up and presented to his partner in parts, with blood dripping out of him. A character is exploded by a land mine. There is extreme, extended peril and violence, and many deaths. Characters use extremely strong language with constant profanity, including racist terms. There are sexual references and situations, including references to impotence and rather homophobic humor. We also see some highly improbable animal sex. Characters drink, and smoke, and at one point it is supposed to be humorous when Marcus gets stoned on Ecstasy. Characters of many races show some prejudice but work together with respect and loyalty and a female character is strong, brave, and capable.

Families who see this movie should talk about how different people decide which risks they will take.

Families who enjoy this movie will also enjoy the original and car chase and explosion movies like “The Transporter” and “Con Air”.