Tires: tire diameter, tire diameter, sidewall height

Question
hi Mr Smith,
I am planning to buy a car that as 18 inches tire. what would happen if i upgrade to 20, 22 inches diameter. do i have better control. is it better with 17 inches instead. i do like larger diameter but i would like to know which is better.

thank you

Answer
Patrick,

As a general rule, increasing the diameter of the rim , while at the same time, maintaining the same overall diameter of the tire, means that the sidewall is shorter - and that generally results in a harsher ride, but a more crisp steering response.  But this reduced sidewall height also results in less distance to absorb impacts.  This means more of a tendancy to bend rims and damage tires.

Cornering power might be increased, but that is more a function of what tire you are replacing and what it is being replace with.