Normal or non normal tire wear
 

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?

I had a cupped tire once on my eclipse, that had similar symptoms to what you wrote.

...whats the weather like? sounds like you might have cold tires. thatd be the tread skipping on tight left and right u-turning that you speak of

Most places or dealerships offer free alignment checks. Do that, but if it's cold, chops is correct
:iagree::iagree::iagree:

Toe?

I would be willing to bet it's cold weather. Summer tires become like hockey pucks when it gets colder out. Mine start doing the same thing as the weather gets colder (Now I have my snow tires on). They would make that same thumping noise almost like they're skipping on the pavement, and it happens even at like 2 mph. It definitely freaked me out when I first started hearing it but did some research and it's common with summer tires in cold/cooler weather (I notice it especially in the mornings leaving for work) And yea on tight diameter turns with the steering wheel turned all the way they would do it a lot. Not aware if it causes any strange tire wear, but in any event if you hear them doing it just make sure to drive slower since your traction isn't nearly as good as it would be in warmer weather.