Understand tire codes

Cracking the Tire Code: A Comprehensive Guide to Numbers and Letters

Have you ever puzzled over the numbers and letters on your tire's sidewall? Fret not – they're your tire's way of communicating essential details. In this all-encompassing guide, we'll decipher both the numerical and alphabetical components, empowering you to make informed choices when it comes to your vehicle's shoes.

Breaking Down the Code:

The series of numbers and letters on your tire's sidewall isn't there to confuse you; it's a roadmap to essential information about the tire. The sequence typically includes details about tire size, construction, speed rating, load index, and more. We'll break down each element to empower you with the knowledge needed to make an informed decision.

cracking the tire codes

Tire Size:

One of the primary elements is the tire size, expressed as a combination of numbers and letters. Understanding this code is crucial – it denotes the tire's width, aspect ratio, and diameter. For example, a tire with the code P215/65R16 breaks down to a width of 215 millimeters, an aspect ratio of 65%, and a diameter of 16 inches.

Aspect Ratio: In 225/40ZR18, the 40 represents the aspect ratio. It's a percentage that tells you the sidewall height relative to the tire width (225mm in this case). So, a 40 aspect ratio means the sidewall is 40% of the tire's width.

Generally, a higher aspect ratio (like 70) means a taller sidewall for a smoother ride, while a lower ratio indicates a shorter sidewall for sharper handling.

What about sizes like 35/12.50R20?

Confusing tire codes can leave you scratching your head. Let's decipher what each number and letter in an unusual tire size like 35 12.50 R20 tells us:

  • 35: This represents the tire's overall diameter in inches when inflated (not under load). In this example, the tire is 35 inches tall.
  • 12.50: This number indicates the section width of the tire, which is the distance between the sidewalls in inches. Here, the tire measures 12.5 inches wide.
  • R: AS you already know, this stands for "radial" construction, the most common type of tire design today.
  • 20: This is the diameter of the wheel the tire is designed to fit, measured in inches. So, this particular tire would fit a 20-inch wheel.

Letters and Their Significance:

Accompanying the numbers, you'll find letters that provide additional insights. The prefix letter, as seen in "P215," specifies the tire's service type. In this case, "P" stands for Passenger, indicating that the tire is designed for passenger vehicles. Other common prefixes include "LT" for Light Truck, "T" for Temporary (spare), and "ST" for Special Trailer. 

Load Index and Speed Rating:

The load index and speed rating communicate the tire's weight-carrying capacity and maximum speed. A higher load index indicates a greater load-carrying capacity, while the speed rating signifies the maximum speed the tire can sustain safely. Balancing these factors is essential to match your vehicle's requirements.

load index table

speed index table

Choosing the Right Tire:

Now equipped with the knowledge of both numbers and letters, selecting the perfect tire becomes a breeze. Consider your vehicle type, manufacturer recommendations, and driving conditions. Whether you're after passenger comfort or off-road prowess, our team at Cheap2Go Tires is ready to guide you to the ideal choice.

Choose your tires with confidence

Expert Tips for Tire Maintenance:

Beyond selection, proper tire care is key to longevity. We'll share pro tips on inflation, rotation, and regular inspections, ensuring your tires not only perform optimally but also last longer.

Empower yourself with the comprehensive understanding of tire markings. Cheap2Go Tires is here to simplify the tire code, making every drive a confident and informed journey. Stay tuned for more insights on tire care and expertise from our team. Have a good trip.