I had imagined that run-flat tires are only available on 17" to 19" rims with particularly thin (aspect ratio-wise) tires. I thought they are engineered by building a slightly thicker rim-facing section, on which the rim would rest when the tire is flat.
But run-flat tires are also available on 16" rims, and they appear to be engineered by adding either circular sections radially or a matrix of rubber to partially fill the void.
Now that my first assumption is gone, I'd like to confirm whether either of my two other assumptions is also incorrect.
Which of the following is not true:
- Run-flat tires contain more mass, and the added rotational inertia would make it ever so slightly harder to accelerate and brake, not to mention that they would consume more gas. Hence you should install them only if you drive a large engine with power to spare, and you don't mind the extra expense and ecological damage.
- It is pointless to install run-flat tires on a car that will be used mostly for city driving, since their "run-flat feature" is only effective for high-speed/highway driving.
(No, no.. these are not two questions. They're one comprehensive question about one problem with more than one facet. I suspect your answer would be comprehensive as well, shedding light on both issues simultaneously.)