Normal or non normal tire wear

evantorch

As I think was/ is true, my 2011 370z coupe-sports package has larger diameter rear Bridgestone tires than the tires in the front.
Although I have owned the car for almost exactly 2 years, I tend to live and work and shop in a small area, so I only have 4500 miles on it (yes, I do wind it out on weekends).

I have always had a puzzling thumping from the tires on very tight left and right U turning which I assumed was somehow a product of the tire size differential--perhaps foolishly---but now I'm seeing wear on the outer front tire treads. The pressures are always kept at correct levels and there is no shimmying on acceleration or deceleration.

Before I head over to check allignments etc. has anyone had this happen or just have suggestions?