Section Height is the vertical distance from the bead seat on the rim to the outer surface of the tread, that is, the height of one sidewall. It is not printed on the sidewall directly but is calculated by multiplying section width by aspect ratio, so a 315/30 tire has a section height of about 94.5 mm. Section height plus wheel diameter determines overall tire diameter and therefore rolling radius, effective gearing and speedometer accuracy. It also governs sidewall compliance, since a taller sidewall deflects more under lateral load, adding compliance and slowing response, while a shorter one is stiffer and more responsive but transmits more impact to the suspension.