What do the markings on my tire mean?

From the size and tire type to the date when your tires were manufactured, there is a wealth of information in the numbers and symbols on your tire's sidewall. Here is a breakdown of what they mean. 

Tire Size 

An image of tires overlaid with numbers representing tire size

If a tire is marked with 235/55R17, this means:

  • 235 is the width in millimetres from sidewall to sidewall.
  • 55 is the aspect ratio, so this means the height is equal to 55% of the tire’s width.
  • R stands for radial construction which refers to how the tires are made.
  • 17 is the rim diameter in inches of the wheel from one end to the other.

Load Index & Speed Rating 

A Ford Mustang overlaid with a number representing speed rating

Using the above example, you would also see '99H' on the tire sidewall.

  • 99 represents the load index – a number that corresponds to the maximum weight a tire can support when properly inflated (for 99, the maximum weight is 775 kg).
  • H is the speed rating that tells you the maximum service speed for a tire. This rating ranges from A – Z. Check with your Ford Dealer for more information about speed ratings. 

Manufacture Date 

A wheel overlaid with a DOT number visible

On the tire sidewall, you will also notice four numbers, often preceded by the letters ‘DOT’. The DOT Tire Identification Number represents the date of manufacture by week and year. For example, if the number was 3616, that means your tires were made in the 36th week of 2016.

Additional Information

What kind of tires should I have for my Ford?
How do I know if I need the tires replaced on my Ford?
How do I check my tire tread?
How do I care for and maintain the tires on my Ford?