Tire Size & Weight Guide

Your vehicle’s tires play an instrumental role in driving safety, as they are the only parts in contact with the road. Yet many drivers don’t give tires a second thought until they wear out or go flat. Of course, we know some car owners find it challenging to understand their tires with all the sizes and varieties available. In addition, tire manufacturers make them for specific uses and particular vehicles. So, we had our tire experts create the following guide to help you understand what tires you should use and why.

How To Read a Tire Size

Red GMC Fleet Truck by Truck Hardware is licensed with CC BY 2.0

To understand your tire’s specification, you must first understand how to decipher the part number or size. Tire specifications vary by the intended purpose and vehicle type. Many drivers replace their vehicle’s tires with the same style because it guarantees a familiar feel and performance. However, you might be surprised to learn that a better option exists.

Every tire has specifications printed on its sidewall. Typically, the specifications will look like P225/75/R18 91V. Knowing what these letters and numbers mean helps you understand the tire’s intended use. For example, the first letter ” P” designates a passenger vehicle tire type. You could find an “LT” instead for light truck. The number after the P tells you your tire’s tread width in millimeters. So, we have a passenger tire with a 225-mm tread width in this case.

The next number in this example, 75, represents your tire’s aspect ratio. The aspect ratio is your tire’s sidewall height, also in millimeters. You should know that high-performance tires have lower aspect ratios than all-season or all-terrain tires.

Next, we have another letter, “R,” for radial. Unless you have a specialty vehicle, you need a radial tire. Following the R, you’ll see another number that indicates the tire’s diameter but not the outside diameter. Instead, it measures the inside diameter of the tire or the part that wraps onto the wheel. Our example has an 18-inch diameter, meaning your wheel must be 18 inches. This tire will not fit on a wheel of any other size.

The following number, 91, represents the tire’s load rating. A tire’s load rating tells you how much weight the tire can support once mounted and inflated. In our example, a 91 load rating can support 1,356 pounds on its own. Multiply that number by four, and your tires can hold up to 5,424 pounds. The final letter “V” stands for your tire’s speed rating or the top speed you can drive on it safely. In this case, the V speed rating can travel up to 149 mph before compromising safety.

Tire Types

Tires differ by manufacturer, yet all manufacturers make tires for specific purposes. Common names include “touring,” “all-season,” “snow.” and “all-terrain.” These names are often printed on the sidewall, but not always. For example, you probably want a touring tire if you live in a warm climate without wintry weather. Touring tires deliver optimal traction on paved roads but less on dirt or other surfaces.

Conversely, you’d benefit from all-season or snow tires if you live in a region with heavy snowfall. Many drivers that experience long periods of snowfall switch out their touring tires for snow tires during the winter months, then switch back again when the warm weather arrives.

Each tire type has tread patterns that provide optimal traction under specific conditions. Thus a snow tire performs best in snowy weather. Keeping your snow tires on in summer won’t impact safety so much as fuel economy. The snow tire tread has more drag than a touring tire, making it less economical.

All-terrain tires have an aggressive tread pattern designed to deliver more traction in sand, mud, and dirt, making them your best option for pickups like the GMC Sierra. In addition, you can safely use all-terrain tires on SUVs if you intend to go off-road often.

Tire Performance

Understanding how and where you drive determines the type of tire you should use. You also need to know what you want in terms of comfort and noise. So, carefully consider what you want your tires to do before installing them.

For example, an all-terrain tire performs well off-road, yet on pavement, this type of tire creates more vibrations and noise and lowers your fuel economy. If you never go off-road, you should use a different tire. Touring tires provide smooth performance with minimal vibrations and noise and deliver better fuel economy. If you own a sports car, you probably want high-performance tires with excellent grip for cornering at high speeds.

GMC and Buick Tire Sizes and Weight Ratings

When choosing a tire, selecting the proper weight rating is essential. So what’s the weight rating for an SUV or pickup truck tire? It would be impossible to include every available GMC and Buick tire’s weight rating in this article. So instead, we created a chart with the most common vehicle and tire size.

As you can see, the weight ratings vary by tire. You want to be sure that when you multiply the tire’s weight rating by four, your rating can hold at least the gross vehicle weight of your GMC or Buick. Our service center professionals can help you determine the proper tire for your vehicle should you have any questions or concerns. We recommend you speak with someone at our tire department if you need to purchase new tires. Then, when you’re ready to have them installed, you can schedule your appointment at your convenience.