TECHNICAL INFO AND DEFINITIONS

It is recommended that the replacement tire size speed rating be equal to or higher than that of the O.E. tire size speed rating. If a lower speed-rated tire is selected, then the vehicle top speed becomes limited to that of the lower speed rating selected. The customer must be informed of the new speed restriction. It is quite common and permissible during winter driving to use a winter tire with a lesser speed rating than the O.E. tire. Still, the customer must be informed of the rating decrease.

Mixing speed ratings on a vehicle is not recommended. If tires of different speed ratings are mounted on a vehicle, the lower speed-rated tires should be placed on the front axle. This is to prevent a potential oversteer condition. Vehicle handling may be affected, and the vehicle’s speed capacity is now limited to the lowest speed-rated tire.

Tires of different size designations, constructions, and stages of wear may affect vehicle handling and stability. For best all-around performance, it is recommended that all tires be of the same size, tire type (summer, all season, winter, all terrain, directionality, etc.), construction (radial or non-radial) and speed rating. Never mix radial and bias-ply tires on the same axle. Get specific information from your Dealer.

No. These tires are specifically designed for warm weather use. When average daily temperatures are at or below 45° F / 7° C, you should make the switch to winter tires.

Winter tires are not assigned tread wear ratings. They are designed for cold weather use only, usually when average daily temperatures are at or below 45° F / 7° C.

While the tire operates just fine in warmer conditions, it will wear out very quickly. The life of the tread is impacted by the amount of driving performed in warmer conditions because the rubber compounds that give this tire winter grip are not designed to withstand non-winter conditions over the long-term. In short, winter tires used in the summer wear out very rapidly.

Avoid used tires. You can never know what hazards and abuse a previously owned tire has suffered. Internal damage can lead to dangerous tire failure.

Plus sizing must be done with proper care. When replacing tires with optional size designations, be sure to check vehicle manufacturer’s recommendations found in the owner’s manual or on the door sticker.  Interchangeability is not always possible because of differences in load ratings, tire dimensions, wheel well clearance and rim size.

However, if you provide the original equipment tire size and the tire size you wish to install to your dealer, they can provide the tire specifications and differences.

The rim width range represents proper rim widths that will assist the tire/wheel assembly in meeting its performance potential. To achieve the best balance between ride, handling and tread wear, select a rim width in the middle of the manufacturer’s range.

To improve cornering traction and steering response, choose a rim at or near the maximum recommended width. The wider the rim width, the straighter the sidewall and the quicker the steering response. Conversely, using a rim width at the low end of the range will cause the tire to balloon or curve out, slowing steering response.

You can calculate proper tire specification on our website.

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, which 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. Below is more information on two of these commonly seen sizing systems.

1. P-Metric
   This is the metric on the tire that begins with P. The P-Metric sizing system was developed to better align with the European tire sizing system and provides a better description of the tire size.
2. European Metric
   This is the metric to the right of the P Metric, following the forward slash. 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 four primary light truck tire sizing systems: Light Truck Metric, Light Truck High Floatation, Light Truck Numeric and Light Truck European Commercial Metric.

1. Light Truck Metric
   This sizing system mirrors the P-Metric system for passenger tires.
2. Light Truck High Flotation
   Light truck high flotation tires have evolved as lower aspect ratio tires and 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.
3. Light Truck Numeric  
   This older system is still widely used, mostly on commercial vehicles.
4. Light Truck European Commercial Metric
   This size system mirrors the European Metric system for passenger tires and is intended for commercial light truck vehicles sometimes referred to as “Euro Vans”. Often these tires are referred to as European C-Type sizes.

DOT signifies that the tire complies with the United States Department of Transportation’s tire safety standards and is approved for highway use.

Example: DOT M5H3 459X 065

1^st and 2^nd Characters: tire manufacturer and plant code

3^rd and 4^th Characters: tire size

5^th-8^th Characters (optional): brand and other significant characteristics of the tire

9^th and 10^th Characters: the week the tire was produced

Final Number(s): the year in which the tire was manufactured

For Uniroyal brand tires, DOT markings related to the week and year of production will have an additional symbol for the decade of the 1990s. It will be shown as a triangle following these last three numbers.

Beginning in year 2000, an additional digit was added to the serial number to allow the year of production to have two digits.

A tire is mounted on the appropriate rim width as identified by T&RA or ETRTO then inflated to 1.8 bar (26 psi). A calibrated measurement tape is run around the circumference of the tire in the center of the tread, which represents the largest overall diameter. This measurement of circumference is then divided by the mathematical constant known as PI (3.14126...) to calculate the diameter.

If no instructions for tire mixing appear in the vehicle owner’s manual, adhere to the following guidelines:

• All four tires should be matched for tire size (unless the vehicle was originally equipped with different sizes on front and rear axles), tire brand and tire model.
• The tire rolling radius or revs/mile should match for all four tires. This can be achieved by having the same tire size, tire brand and tire model on all four wheels.
• Do not mix tire types such as all terrain, all season or winter.
• A single tire can be replaced even if the other three tires are worn as long as:
  • It is not contrary to the vehicle manufacturer's recommendation/owner's manual
  • All four tires have the same size, brand and model.
  • The difference in tread depth does not exceed 5/32".
• Note: tire rolling radius (or rev/mile) is sensitive to tire inflation pressure.  All tires should be properly inflated.

Tires with directional tread patterns must be mounted so that the primary direction of rotation matches the directional arrows on the tire sidewall. If all four tires are the same size, directional tires can be rotated front to back.

Tires with tread patterns that are both asymmetric and directional require left and right specific tires. Sidewall markings will identify the side of the vehicle and the primary direction of rotation for the tire. If all four tires are the same size, they can be rotated front to back.

P-metric sized tires are those with the "P" at the beginning of the tire size (such as P215/65R16). P-metric sizes were introduced in the United States in the late 70s and are installed on vehicles primarily used to carry passengers including cars, station wagons, sport utility vehicles and even light-duty pickup trucks. Their load capacity is based on an engineering formula which takes into account their physical size (the volume of space for air inside the tire) and the amount of air pressure (how tightly the air molecules are compressed). Since all P-metric sizes are all based on the formula for load, vehicle manufacturers can design their new vehicles (weights and wheel well dimensions) around either existing or new tire sizes.

Metric or Euro-metric tire sizes are the ones without the "P" at the beginning, (such as 215/65R16). Using metric dimensions to reflect a tire's width actually began in Europe in the late 60s. However, since Euro metric sizes have been added over time based on the load and dimensional requirements of new vehicles, the tire manufacturers designed many new tire sizes and load capacities around the needs of new vehicles. Not quite as uniform as creating sizes using a formula, but they got the job done.

Euro metric and P-metric tires in the same size (i.e. P215/65R16 and 215/65R16) are equivalent in their dimensions with just slight differences in their load capacity calculations and inflation pressure tables.

Excessive wheel spinning, when freeing a vehicle from sand, mud, snow, gravel, ice or wet surfaces, can result in explosive tire failure, causing serious personal injury or vehicle damage. Do not exceed 35 MPH (55km/h), as indicated on the speedometer. Never stand near, or behind, a tire spinning at high speeds when attempting to push a vehicle that is stuck.

Never exceed the load-carrying limits molded on the sidewall of the tires or the maximum vehicle axle load limit as shown on the vehicle tire placard, whichever is less. Overloading builds up excessive heat in the tire and could lead to failure.

The speed rating of a tire indicates the speed category (or range of speeds) at which the tire can carry a load under specified service conditions. The speed rating system used today was developed in Europe in response to the need to categorize tires into standardized speeds. A letter from A to Z symbolizes a tire's certified speed rating, ranging from 5km/h (3 mph) to above 300 km/h (186 mph).

The DOT symbol certifies the tire manufacturer's compliance with the U.S. Department of Transportation’s tire safety standards. Tires manufactured for use in the United States and Canada have the full DOT serial number located on one sidewall near the rim. A partial DOT serial number will appear on the opposite side of the tire.