Ford Tires Centre in Vegreville, Alberta
There is a wealth of information on the sidewall of your tires. From size and type to the date they were manufactured.
In the photo above (235/55R17) We can see the following information. 235 is the width in mm from sidewall to sidewall. 55 is the aspect ratio. This means the height of the tire is equal to 55% of the tire’s width. R = Radial Construction. And 17 is rim diameter in inches of the wheel from one end to the other.
Again, using the example above we see 99H. The 99 represents the load index. This corresponds to the maximum weight a tire can support when properly inflated. (for 99, the maximum weight is 75kg) H is the speeds rate indicating maximum service speed for the tire. In this case H = 210km/h (this is not recommendation to exceed speed limits)
Lastly, you will find 4 numbers preceded by the letters DOT. The DOT Tire Identification number represents the date of manufacture by week and year. So for example, if the number is 3616 the tire was made in the 36th week of 2016.
For more information, check out Wikipedia Tire Code explanations here.