Tire Shopping: Understanding Your Options

 

Tire ShoppingTire Code Part 2:  Aspect Ratio, Tire Construction, and Wheel Diameter

It is important to familiarize yourself with the differences between the many available tire types when shopping for new tires. In this three-part series, we are looking at the tire code that is imprinted on all tires. Each part of the tire code alpha-numeric sequence identifies something about the tire. Being able to interpret that code can help you choose the best tires for you.

Aspect Ratio

The aspect ratio of a tire is calculated by dividing a tire’s section height by its section width when the tire is:

  • inflated to proper air pressure
  • mounted on the approved measuring rim
  • under no load

The aspect ratio affects steering stability. Generally, the shorter the sidewall, or the lower the aspect ratio, the less time it takes to relay the steering input from the wheel to the tire, for faster steering response. Aspect ratio also affects the tread contact patch. A low-profile tire typically produces a wider tread contact patch. This wider tread contact patch creates a firmer footprint that provides improved cornering traction.

Tire Construction

The construction of the tire is identified by the letter following the aspect ratio. The most common designation is R, which stands for radial construction. Other, less common construction types for modern passenger cars may include D for bias ply construction and B for belted tires.

Wheel Diameter

The number following the construction code indicates the size of the wheel that the tire will fit in inches. Tire sizes on most vehicles begin at 13-inches and go up to 18-inches. Custom package wheels can be 22-inches or even larger.

An important sizing calculation in tire fitting, aspect ratio should be considered with wheel diameter for the best tire and wheel combinations. Lower aspect ratio typically indicates a high performance tire, with better lateral stability. Most of the new tires will be marked R for radial construction, however if you are replacing old tires, you may see the D or B designations.

When considering aspect ratio, tire construction, and wheel diameter, you should always select your vehicle manufacturer’s recommended specifications to assure safe and optimal tire performance. Just as choosing a dependable, quality tire is important, it also necessary to choose one that is developed for the best performance given the weight and design of your vehicle.

Next Up: Tire Code Part 3:  Load Index, Speed Rating, and Use Designation.

Tire Shopping: Understanding Your Options

Tire Shopping: Understanding Your OptionsShopping for tires can be a little overwhelming with the wide range of styles and choices that are available. It is important to choose the right tire for your vehicle and the type of driving you do in order to get the best safety, performance, and gas mileage from your vehicle. So, how do you go about choosing the right tires?

Getting to know the differences between the many tire types that are out there is a great place to start. In this three-part series, we will look at the tire code that is imprinted on all tires. Each part of the tire code alpha-numeric sequence tells you something about the tire. Understanding that code can help you find the right tires.

Tire Code Part One: Tire Type and Section Width

Type of Tire

The type of tire and it’s intended use are indicated by the first letter in the code. Letter designations include P for passenger vehicles, T for temporary spare, LT for light truck metric, C for commercial, and ST for special trailer service.

Section Width

Following the tire type letter is the section width of the tire, which is listed in millimeters. This is the widest point from sidewall-to-sidewall, so a larger number indicates a wider tire.

The proper size and tire type are important to assure safety and the best tire performance. Buying a quality tire will not guarantee the best performance if the tire is not made to accommodate the weight and design of your vehicle. Also, since tire size is a factor in the calculations of the computerized functions of today’s vehicles, it is essential to install the recommended tire size.

Next Up: Tire Code Part 2:  Aspect Ratio, Tire Construction, and Wheel Diameter