This is shaping up as one of the most unpredictable weekends of the summer, and early tracking isn’t bringing much clarity.That’s because Disney/Pixar’s “Cars 2″ is throwing most B.O. pundits for a loop in advance of its Friday bow. Not so difficult to predict: Sony’s R-rated laffer “Bad Teacher” is on track to score similar to “Bridesmaids,” which took $26 million in its opening weekend. That would put “Bad Teacher” in a solid spot, considering the pic’s reported budget at just under $20 million. “Cars 2″ has plenty of positives in its corner (i.e., the prestige of the Pixar brand and mega-lucrative merchandising) to suggest a healthy No. 1 launch. Its predecessor earned $60 million in its June 9, 2006, opening, but a bow that high isn’t likely, according to pre-weekend tracking services. Why? First, family-driven films are difficult to predict since kids — responsible for the nag-and-drag effect — don’t figure in pre-release tracking (that’s the domain of parents and young adults). Also, “Cars 2″ is likely to skew much younger (and mostly to boys) than a franchise like “Toy Story,” which benefited from widespread interest among general audiences. So it’s no surprise that “Cars 2″ isn’t pulling massive tracking numbers. But rival studios advise not to bet against the toon, which could still see a spike in interest before Friday. (Disney isn’t revealing its expectations until Thursday.) Regardless of how the film opens, “Cars 2″ should continue to hit high multiples at the box office, not to mention reap colossal coin on storefronts.