What do tire size numbers mean?
The size breaks down into three numbers. Using our example size, 205/55 R16, this is what each number means:
205 is the width of the tyre tread in millimetres. This goes up in increments of 5. WhatTyre’s Search By Tyre Size function allows you to select widths between 165 and 305.
55 refers to the profile of the tyre, or the distance between the wheel and the edge of the tyre, looking at it from the side. The number is the percentage of the width of the tyre. It is commonly known as the “aspect ratio”. So, the profile of our example tyre is 55% of 205mm, or 112.75mm. This number also increases in increments of 5.
16 is the rim size, or the diameter of the inside of the tyre. It is expressed in inches and increases in increments of 1. WhatTyre’s Search By Tyre Size function currently allows you to search for tyres with rim sizes from 13 to 24.
WHY IS THERE AN R IN THERE?
The letter R means “radial” which is the way the tyre is constructed.
WHAT DO THE NUMBERS AND LETTER AFTER THE TYRE SIZE MEAN?
Congratulations! You are officially interested in tyres.
These figures show the limits of how you can use the tyre. The number is the “load index”, or how much weight the tyre can carry.
The letter is the speed rating. This tells you the maximum speed the tyre is suitable for. This is the fourth and final part of your WhatTyre tyre search. Most car tyres for road use have a maximum speed between 118mph (T) and 187mph (Y).
Therefore, our example tyre has a maximum speed of 150mph as it has the speed rating V. The load index of 91 means it can carry a load of 615kg.