What do the markings mean on the side of my tyre?
For the purposes of this question, let’s say a 205/55 R16 91V:

• 215: This is the tyre width in millimeters.
• 60: This is the height or profile of the tyre sidewall (aspect ratio), expressed as a percentage of the tread width. In this case, the height of the tyre sidewall is 205×0.55 = 112.75mm.
• R16: Here’s the diameter of the wheel rim, measured in inches – the wheel rim is 16″ in this case.
• 91: This is the ‘load rating’ of the tyre. It’s a measure of the maximum weight it can support. 91 denotes a load rating of 615kg.
• V: The speed rating of the tyre. I.E. the maximum speed at which the tyre can support maximum load. This should be higher than the maximum speed of the car. In this case, ‘V’ means a speed rating of up to 149mph.