How do I read the sidewall of my tire?
The side of a tire contains information needed for your safety and that of your customer. Being able to read sidewall markings will help you better understand the performance of each tire. It will also provide you with information when mounting and servicing the tire.
Passenger Tire Sizing
Three primary sizing systems exist for passenger tires today: P-Metric, European Metric and Millimetric. Each of these systems evolved from the first tire sizing system-the Numeric Sizing system-that is now obsolete. It was developed when all tires had the same aspect ratio, and it provided only the nominal cross section width of the tire and the rim diameter in inches. The following are examples that identify the three sizing systems that are commonly seen today.
The P-Metric sizing system was developed to better align with the European tire sizing system. It provides a better description of the tire size. See examples below.
Essentially, this system was a conversion of the Numeric system from inches to millimeters. Aspect ratio appears in the size designation in most cases where it is other than 82.
Light Truck Tire Sizing
Sizing for light truck tires takes the performance requirements of the vehicle, and the tires, into account. Light truck tires have evolved along with the expanded applications of trucks and vans that have grown to be multi-purpose vehicles that we use for work, for recreation or as passenger vehicles.There are three primary light truck tire sizing systems: Light Truck Metric, Light Truck High Floatation and Light Truck Numeric.
Light Truck Metric
This sizing system mirrors the P-Metric system for passenger tires.
Light Truck High Flotation
Light truck high flotation tires have evolved as lower aspect ratio tires became more popular on light trucks. The combination of lower aspect ratios and high flotation yielded better traction on sand and soft soil found in off-road situations.
Light Truck Numeric
This older system is still widely used, mostly on commercial vehicles.