How can I tell what size a tyre is?

Question

Accepted Answer

Tyres sizes can be found on the tyre label and are defined by a number of variables; an example of which could be:

385/65 R22.5 160K

385: Width of the tyre in millimeters.
65: Aspect ratio, meaning the sidewall height is 65% of the tyres width.
R: Tyre construction (Radial in this case).
22.5: Diameter of the rim the tyre fits in inches.
160: Load index, indicating the maximum weight the tyre can carry (see load index charts online).
K: Speed rating, indicating the maximum sustained speed the tyre can handle (see speed rating charts online).