Select dimensions of tyres to determine the overall diameter
Matching overall diameters when changing wheel & tyre sizes is necessary to ensure ride height and gearing don't change
Use the TAB key to move between the fields then the ARROW keys to select the values
(SHIFT+TAB reverses direction of selection) or use the MOUSE to select from the Drop Down Boxes Site Index & Enquiries
Other Technical links: Tyre Speed Ratings || Vehicle Wheel Fitment