Commenting on old VTA tires being a smaller diameter than new tires...
Actually the opposite can also be true....... Believe it or not, depending on what chemicals you are using to clean your tires and what traction compound you use, the VTA tires can grow (swell) larger in diameter compared to new tires. It is enough to affect your ride height and overall gearing rollout.
New tire on the left, used (but not worn out by a long shot) tire on the right.
