When i put 15" speedlines on i noticed the car tramline alot meaning it follow the road grooves more. If there all balanced, check the suspension components....then go for a laser wheel alignment. most drivers tend to hit potholes and 4x4 there cars on to massive curbs all of which doesnt help wheel alignment and over time it knocks it out so this could be your problem i went from 15" to 14" and it felt more apparent that the wheel alignment was out for future ref avoid potholes like the plague, avoid driving the car over curbs if it has to be done do it as slow as possible or reverse onto it.