I just mounted a new set of 285/50r20 cooper zeon ltz on 20x12 moto metal 962s. I took them to a shop to have them balanced and they got 3 of them just fine with 5-6 oz but the fourth one they said was off by 370 oz and they couldn't balance it. Is it more likely that I have a bad wheel or a bad tire? They weren't much help in diagnosing the problem, I'm guessing because I didn't buy my wheels or tires there.. Any help would be appreciated.