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What Tire Size Outside Diameter Chart: All You Need to Know.

October 29, 2023

The tire size outside diameter chart is a tool used to determine the diameter of a tire based on its size specifications. By consulting this chart, it is possible to compare different tire sizes and find the best fit for a vehicle.

Tire size is a critical aspect of vehicle performance. A tire that is too large or too small for a vehicle can negatively impact handling, fuel economy, braking, and acceleration. To avoid these problems, it is important to understand how tire size is measured and how to use the tire size outside diameter chart to find the best match for your vehicle.

This chart lists tire sizes according to their nominal width, aspect ratio, and rim diameter. By comparing these specifications to the chart, you can determine the outside diameter of the tire and ensure that it is the correct size for your vehicle.

What Tire Size Outside Diameter Chart: All You Need to Know



    Understanding Tire Sizes

    Tires are an essential component of any vehicle, and knowing the correct dimensions is crucial. Tire sizes are usually displayed on the sidewall of tires, and they can be a bit confusing, with a combination of letters, numbers, and symbols.

    This section will explain the key terminologies for tire sizing and provide a guide on how to read a tire size outside diameter chart.

    Explanation Of Tire Size Terminology

    • Tire type: Refers to the type of vehicle for which the tire is intended, such as passenger car (p), light truck (lt), or temporary use spare (t).
    • Aspect ratio: Describes the height of the tire’s cross-section as a proportion of the tire’s width. For instance, an aspect ratio of 60 means that the height of the tire is 60% of the tire’s width.
    • Rim diameter: The diameter of the wheel on which the tire will fit, measured in inches.
    • Load index: This rating indicates the maximum weight that a tire can support when adequately inflated. The higher the number, the greater the weight the tire can carry.
    • Speed rating: This indicates the maximum speed at which the tire can safely operate. Speed ratings are a letter from a to z, with a being the slowest and z the fastest.

    How To Read A Tire Size Outside Diameter Chart

    The tire size outside diameter chart helps you choose the correct size for your vehicle. Here’s how to read it:

    • Locate your vehicle’s make and model in the chart: Look for your car’s make and model in the first column of the chart.
    • Check your tire’s rim diameter: The rim diameter is found in the second column of the chart. Ensure that it matches your vehicle’s recommended rim diameter.
    • Check your tire’s aspect ratio: The aspect ratio is located in the third column of the chart. Ensure that it matches your vehicle’s recommended aspect ratio.
    • Check your tire’s load index and speed rating: These figures are located in the final column. Ensure that they match your vehicle’s specifications.

    Importance Of Knowing Your Vehicle’S Recommended Tire Size

    Using the correct size of the tire is crucial for several reasons. First, the recommended tire size ensures optimal vehicle performance, including fuel efficiency, safety, and ride comfort. An incorrect tire size can affect the speedometer’s accuracy, cause low gas mileage, and decrease your vehicle’s braking and handling capabilities.

    Moreover, tire sizes affect the vehicle’s load-carrying capacity, and using the wrong tire size may cause the tire to overload. Overloading the tire may lead to tire failure, and under no circumstances should you overload the tire.

    Common Tire Sizes For Different Types Of Vehicles

    Tire sizes vary depending on the type of vehicle. Here are a few common tire sizes used for specific vehicle types:

    • Passenger cars: 195/65r15
    • Suvs and crossovers: 225/60r18
    • Pickup trucks: Lt245/75r17
    • Sports cars: 225/45r18
    • Compact cars: 185/70r14

    Impact Of Changing Tire Sizes On Performance

    Changing your tire size can affect your vehicle’s performance in numerous ways. For instance, installing larger tires than your vehicle’s recommended size may increase the speedometer’s inaccuracy, decrease acceleration, and reduce the vehicle’s load-carrying capacity.

    On the other hand, smaller tires than the recommended size may impact your vehicle’s fuel efficiency and handling over rough terrain. It’s important to consult with an expert to ensure that you are using the correct tire size for your vehicles.

    Understanding tire sizes can have a significant impact on your vehicle’s performance, so it is crucial to ensure that you know your vehicle’s recommended tire size. Always check the tire size before purchasing to ensure that it matches the recommended size and follow the manufacturer’s guideline for installation.

    Factors To Consider When Choosing Tires

    Selecting the appropriate tires is vital not only for vehicle performance but also for the driver and passenger’s safety. The following are essential factors that one should take into account when choosing tires:

    Tread Wear, Traction, And Temperature Ratings

    Tread wear, traction, and temperature are the key components of your tire’s performance. The following are some essential points to consider:

    • Tread wear rating measures how long the tire will last before requiring replacement. The higher the rating, the longer the tire’s lifespan.
    • Traction grades evaluate a tire’s ability to stop on both wet and dry road conditions. Traction ratings are graded based on the letter a, b, or c, with a being the highest and c being the lowest.
    • Temperature rating is used to indicate a tire’s ability to dissipate heat under load conditions. The higher the temperature rating, the better the tire’s ability to dissipate heat.

    Load Index And Speed Rating

    Load index and speed rating are crucial factors in selecting tires that can carry the weight and velocity of a vehicle. Here are some key things to keep in mind:

    • The load index indicates how much weight a tire can bear and is expressed as a numerical value. A higher number means a tire can support more weight.
    • Speed rating helps drivers to make sure they choose tires that match the speed rating of their vehicles. Speed ratings are expressed as letters, with higher letters indicating a higher speed capacity.

    Tire Construction Types

    Tire construction types play a significant role in determining the overall quality and durability of a tire. The following are some critical points to consider:

    • Radial tires are the most common tire type. They have layers running perpendicular to the tire’s direction of rotation, providing improved steering control, and a smoother ride.
    • Bias ply tires are more durable than radial tires and are used in off-road vehicles due to their excellent off-road traction.

    Application-Specific Factors

    The choice of tires depends on the type of application for which they are needed. Here are a few examples:

    • Winter or snow tires are perfect for cold weather and snow-covered roads.
    • Performance tires are optimized for handling and speed and are ideal for racing or sports cars.
    • All-season tires are versatile and capable of performing well in a range of conditions.

    When choosing tires, it is important to take into account all the above-mentioned factors and assess them according to your vehicle, driving habits, and the prevailing weather conditions in your area. Following these guidelines can make the difference between a safe and comfortable ride and a potentially dangerous one.

    How To Measure Tire Size Outside Diameter

    What tire size outside diameter chart: all you need to know

    As a car owner, knowing your tire size outside diameter is vital knowledge. It comes in handy when buying new tires or even verifying what size tires you currently have on your vehicle. In this section, we will discuss how to measure tire size outside diameter, the tools required for measuring, and tips to ensure you take accurate measurements.

    Step-By-Step Process For Measuring

    To measure tire size outside diameter, you need to follow these simple steps:

    • Locate the tire’s sidewall: Start by finding the tire size information on the outside wall of the tire.
    • Look for the size code: The tire size code usually starts with a letter, which represents the tire type or its purpose. For example, “p” denotes a passenger vehicle tire.
    • Identify the width: Locate the three-digit number next in line after the tire code letter. This number is the tire’s width in millimeters.
    • Find the aspect ratio: The aspect ratio is the second set of numbers in the size code and is a percentage. It is the height of the tire’s sidewall relative to its width.
    • Determine the tire construction: The tire construction can be either “r” or “d.” “r” refers to radial construction, while “d” refers to diagonal or bias-ply construction.
    • Calculate the outside diameter: To calculate the outside diameter, use this formula: width x (aspect ratio ÷ 100) + (rim size in inches x 2.54).

    Tools Required For Measuring

    The following tools can be used to measure tire size outside diameter:

    • Measuring tape: You can use a measuring tape to measure the width and aspect ratio of the tire.
    • Rim: A rim can be used to measure the tire’s diameter. Place the rim against the tire and measure its diameter using a tape measure.

    Tips For Ensuring Accurate Measurements

    To ensure that you get accurate measurements, here are some tips to follow:

    • Measure at the widest point: When measuring the tire width, ensure that you take the measurement at the widest point of the tire.
    • Measure when the tire is cold: It is essential to measure tire size outside diameter when the tire is cold since tires tend to expand when they get hot.
    • Use the right tools: Always use the correct tools for measuring, as using uncalibrated tools can give inaccurate sizes.
    • Be careful: Take your time when measuring your tire size outside diameter. Any error can lead to purchasing the wrong size, which can be expensive.

    Measuring your tire size outside diameter is a simple process that you can do yourself. Always ensure that you use the correct tools and follow the tips we have discussed to get accurate measurements. Knowing your tire size outside diameter can come in handy when it comes to buying new tires or even verifying the size of your current tires.

    Tire Size Conversion Chart

    If you’re confused by the different tire sizes, you’re not alone. Understanding the numbers and letters on your tire’s sidewall can be challenging. Fortunately, a tire size conversion chart can help. Here is a breakdown of everything you need to know about using a tire size conversion chart.

    Explanation Of Tire Size Conversion

    Tire size conversion refers to the process of determining the equivalent tire size in a different measurement system, such as switching from metric to inches or vice versa. To use a tire size conversion chart, you need to know your tire’s current size and either the metric or inch system you want to convert it to.

    For instance, when you see “215/60r16” on your tire, you’re looking at the size in the metric system. Each number represents the tire’s dimensions, and you can find a chart with the appropriate conversions to translate those numbers into the inch system.

    Tips For Using A Tire Size Conversion Chart

    Using a tire size conversion chart might seem daunting, but with a couple of helpful tips it won’t be a problem:

    • Always check the tire manufacturer’s recommendations before buying a tire. They’ll have a suggested size, which will ensure maximum safety and performance.
    • Cross-check the tire size conversion chart with your vehicle’s manual or speak to a tire professional to ensure you’re making the right choice. There may be limitations on tire size, depending on your vehicle’s make and model.
    • If you’re buying replacement wheels for your car, make sure the new wheels have the same hub diameter, bolt pattern, offset, and backspacing as your stock wheels.

    Importance Of Consulting A Professional When In Doubt

    It is vital to consult with a tire professional when using a tire size conversion chart. When in doubt, it is critical to seek an opinion from an experienced tire dealer. They can provide you with more information and guide you in the right direction.

    Making sure you have the right tire size is crucial for your safety and the longevity of your vehicle. A trained expert will be able to look at your vehicle and understand better what tire size meets your needs. It’s never worth risking getting the wrong size, which could lead to potential safety hazards.

    So be sure to have a professional opinion in case of any doubts.

    Using a tire size conversion chart can be a lifesaver, but only if you understand how to use it correctly. Stick to the manufacturer’s guidelines and consult with a professional when in doubt to ensure that you pick the right size for your vehicle.

    Frequently Asked Questions For What Tire Size Outside Diameter Chart

    What Is Tire Size And Outside Diameter?

    Tire size is the measurement of the tire’s width, aspect ratio, and rim diameter. The outside diameter is the overall height of the tire measured and includes the tread.

    How Do I Know My Tire’S Outside Diameter?

    To determine the outside diameter of the tire, locate the number on your tire’s sidewall that indicates the rim diameter. Then, multiply this number by two and add the height of the tire tread.

    Do Different Tire Sizes Have Different Outside Diameters?

    Yes, the outside diameter of the tire changes with size. A tire with a smaller rim diameter will have a larger outside diameter than a tire with a larger rim diameter, all other factors being equal.

    Why Is Tire Outside Diameter Important?

    The outside diameter of a tire is significant because it affects the speedometer and odometer’s accuracy. A tire with a larger outside diameter rotates fewer times per mile, while a smaller tire must rotate more, leading to an inaccurate reading.

    Can I Change My Tire Size Without Changing The Outside Diameter?

    You can change your tire size without affecting the outside diameter by using a tire with a different aspect ratio. This maintains the same rim diameter and outside diameter, but changes the tire’s width and height.

    What Happens If I Use The Wrong Tire Size Outside Diameter?

    Using an incorrect tire size outside diameter can cause issues with the speedometer, odometer, and overall driveability of your vehicle. It can also lead to tire wear and tear, affecting the longevity and safety of your tires.


    As we come to the end of this article, we hope that you’ve gained a wealth of knowledge regarding tire size and outside diameter. Tire size is not only a crucial factor when it comes to selecting new tires, but also it can have a tremendous impact on your vehicle’s performance.

    Knowing how to read and interpret a tire size chart, as well as the outside diameter, will help you make an informed decision about the right tire size for your vehicle. By taking into account the factors discussed in this article, you can ensure that your tires are not only the perfect fit for your vehicle, but they’re also safe and optimal for your driving needs.

    Don’t let the process of finding the ideal tire size be daunting – utilize the information and tools at your disposal and find the tire size that works best for you and your vehicle.

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