4lb tire weight saving - impact on performance?
 

If I were to reduce unsprung weight by 16 lbs (4 lbs for each tire) by switching to a lighter load tier 93Y vs 97Y, what would that do for performance?

I think you'll see some benefit, provided the performance level of the two tires are comparable, acceleration and brakng should improve.

http://www.caranddriver.com/features...sted-tech_dept

It depends on the vehicle...

The heavier the vehicle, the less effect it will have...

Shaving 4 lbs per tire on your relatively heavy GS460 will make little difference...

Shaving 4 lbs per tire off a stripped down Miata that is outfitted for auto cross, big difference...

You probably will not notice the difference in your car at all...