No idea what all those numbers and letters mean on the side of your tire? They say a lot about what kind of tire you have and what it can do. Let's use P21560R16 as an example:
“P” stands for “passenger.” Most vehicles will have a “p” but some trucks will recommend an “LT” for “Light Truck.”
215 represents the section width of the tire or how wide the tire should be mounted on the proper rim with the proper air pressure.
60 is the aspect ratio or the height of the sidewall divided by the width of the tire. The sidewall is very important because it helps to keep the shape of the tire.
“R” stands for radial design referring to the how the tire is constructed. There is a bunch of steel cords under all that rubber and “radial” references how they are weaved together to prevent tire punctures according to where you drive. Most passenger or everyday vehicles have a radial design.
And lastly “16” refers to the size of rim that this tire can be fitted to. Tires can have anywhere from a 14”-20” rim depending on the vehicle.
To find what tire your vehicle requires you check the placard on your door panel or your owner's manual.