Your tires are the most important thing on your vehicle. They are the only contact point between you and the road, and they dictate more often than not how your vehicle brakes, how it handles and how it responds to emergency situations.
When you first purchase your vehicle, your tires are perfectly adapted to how your vehicle was engineered. When the moment comes to replace your tires, you have to make sure you buy the proper type. Here’s how you make that determination.
If you look at your tires, you will find a marking that looks something like this: P225/65R15 95H.
The first letter represents the type of tire. Most of the time, you will see a P which means this tire is made for passenger vehicles and complies with all regulations.
The numbers that follow represent the tire width, in this case 225 millimeters. The second number is the aspect ratio which compares the height of the tire to its width. So for example, 65 here means that the height of the tire is 65 % of the size of the width. The letter that follows refers to how the tire is constructed. This will generally be the letter R because the layers of the tire run radially across. Then we have the wheel size, in this case 15 inches.
Then we have the last two numbers and the letter. The first numbers represent the maximum load a tire can bear when fully inflated while the final letter is the tire speed rating. Here is a chart explaining speed ratings:
Q : 160 km/h
R : 170 km/h
S : 180 km/h
T : 190 km/h
U : 200 km/h
H : 210 km/h
V : 240 km/h
W : 270 km/h
Y : 300 km/h
Z : More than 240 km/h
Thank you to South Centre Volkswagen for their help with this article.