As mentioned above, the letter P (and sometimes no letter, as in the case of the pictured tyre) denotes the tyre is indicated for use in passenger vehicles. LT, on the other hand, means the tyre is rated for Light Truck use.
This number usually follows the letter P or LT and it means the width of the tyre, measured from sidewall to sidewall. In the case of the tyre pictured the width is 205mm
This is the next number along and, in the case of the tyre pictured which is showing 65, means that the height of the tyre is equal to 65% of the tyre’s width
This tells you how the tyre has been made. So, in the case of the pictured tyre, the R stands for radial-ply which means the plies run radially across the tyre from bead to bead. An B indicates the tyre is of a bias construction which means the plies run diagonally across the tyre from bead to bead, with plies alternating in direction for reinforcement
This is indicated by the R (and a number) and, in the case of the pictured tyre R15 suggests the wheel rim is 15 inches. If you’re buying a new set of tyres for your car this is the size you’ll need
This tells you the maximum speed at which the tyre can carry its load (the load is indicated in pounds – elsewhere on the tyre sidewall you’ll find the load rating in pounds and kilograms). In the case of the pictured tyre which shows 91V, the tyre has a speed rating of 240km/h. Despite this rating, you should, of course, always drive the sign-posted speed limits.
Z: More Than 240km/H
This number means the tyre is compliant with applicable safety standards established by the US Department of Transportation, or DOT. Adjacent to this is a tyre identification or serial number