Does lowering a tire's aspect ratio improve performance?

Answer 1

All things being equal, yes.

A tire with a lower aspect ratio (sidewall height) will have a stiffer sidewall with less flex under load. Less flex equals sharper and faster steering response and improved braking performance.

A lower profile tire will also frequently have a more squared-off shoulder and thus a greater tread-width for a given size, thus giving a wider contact patch for better grip and handling. Take for example the Bridgestone Insignia SE200. In a P205/70R15 95S size this tire has a tread width of 6.3 inches. In a P205/65R15 92S size (lower profile but same section width) the tire has a tread width of 6.5 inches.

The downside of lower profile tires is of course harsher ride and reduced load carrying capacity (typically) which requires careful choice of the correct size and inflation pressure for each application.

Answer 2

Yes going from 75 series to 50 profile tires gears the car lower more revoultions of the tire per mile. And if you lower the side wall and replace the rimd with wider wheels one inch taller you gain both ways more rubber on the ground and lower gearing.

Answer 3

not really! its more power the asphalt but more distance to cover {physics}