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Tire Aspect Ratio Explained

Tire size - tire aspect ratio highlighted

In every tire dimensions explained guide, readers will find the meaning of each number located on the tire's sidewall. We will not break that trend! However, we will focus on expanding on the aspect ratio of tires.

With car tire sizes, both the tire height and width, as well as the rim diameter are important. Learning how to measure tires is a life skill every driver should know.

Don't worry! We will explain tire size numbers and everything else you need to know regarding them.

What Is the Aspect Ratio of a Tire?

The aspect ratio of a tire means the height of the tire's sidewall. It is the second number in the tire size, which is shown as the percentage of the tire's footprint width. This tire size measurement determines how tall a tire will be in the end.

What Does the Second Number in a Tire Size (Aspect Ratio) Mean?

Let's take 235/80R16 as an example.

The first number on tire size is the footprint width measured in millimeters, 235 mm in this case. The tire size ratio is the number following that, shown in percentages. This means that the sidewall height is 80% of its width. Lastly, you have the rim diameter, which is 16".

In order to explain tire sizes completely, especially the aspect ratio, we need to bring out a calculator.

How to Calculate Tire Aspect Ratio?

Yes, it can get confusing that tire dimension is measured in millimeters, percentages, and inches. But, we can't really change industry standards. What we can do is learn to navigate the complicated topic of tire measurements to correctly calculate tire height, width, and rim diameter.

When it comes to the aspect ratio, tire measurements are crucial - mainly the footprint width. In a car tire size, the aspect ratio is the percentage of the tire width, so we need to know how to navigate.

Tire Dimensions Made Simple

Let's pretend that search engines do not exist for a moment, and we cannot ask them to convert millimeters to inches. What do we do then?

In order to convert millimeters to inches, you need to divide them by 25.4. If we take the 235/80R16 again, it will be 235/25.4 which results in 9.25".

Then, the next step in calculating tire size dimensions is looking at the aspect ratio. Therefore, you need to multiply tire width with the middle number in tire size as a percentage. It will go something like this:

235mm x 0.80 = 118mm or 9.25" x 0.80 = 7.4"

So, the height of the sidewall is about 7.4".

Tire size explanations

What Is Tire Height? (Actual Tire Dimensions)

The aspect ratio is not the actual tire diameter. The full dimensions of a tire are the tire sidewall twice plus the rim diameter. This means for 235/80R16:

7.4" x 2 = 14.8" + 16" = 30.8"

Taking this method to any other tire size example will give you a tire measurement estimation, helping you choose the correct tire sizes.

When it comes to understanding tire dimensions, it is important to note that this math is not foolproof. Actual tire ratios can differ depending on the manufacturer and the tire type.

Why Tire Sidewall Height Matters

The second number on tire size determines whether the tire is a low-profile tire or a regular one. As such, when we define aspect ratio we want, it will also determine how the vehicle will perform.

Tires with taller sidewalls have more rubber that cushions the vehicle during the drive. It guarantees a smoother performance. On the other hand, shorter tire size specs offer sharp controllability and high speed durability.

Various characteristics come with different tire sizes and aspect ratios. Therefore, understanding tire measurements will help drivers choose what's best for their vehicles and driving style.

Tire Aspect Ratio and Performance

Every tire dimensions guide will tell you there is a correlation between tire size and a vehicle's performance. This is the reason different vehicles need distinct tires.

In order to understand tire size numbers, we must mention how the second number in tire size affects the vehicle's performance. Smaller sidewalls create larger road contact areas, and vice versa, and this promotes versatile tire characteristics.

The Effect of Tire Ratios Explained:

  • Shorter sidewalls result in sharp steering and better controllability compared to taller tires
  • A low aspect ratio results in higher rolling resistance, which can ruin fuel efficiency
  • Taller sidewalls lessen road vibrations felt by the passengers in the vehicle's cabin
  • Braking, cornering, and maneuvering are increased with smaller aspect ratio tires

Choosing the Correct Tire Aspect Ratio for Your Car

Once we understand tire sizes and their importance and correlation to a vehicle's performance, it is time to think about what we want out of our ride. Comfort and excellent fuel economy? Maybe high speed handling and stronger cornering?

Whatever it may be, it is important to know that even the tire size middle number can ruin our expectations, if we do not choose wisely. True, changing the entire tire size will be costly (as most likely the rims will be switched too), but it is a worthwhile investment to get the performance you want.

Yes, measuring tires will let you know what you can expect from low-profile tires vs. regular tires.

High Profile Tire vs. Low Profile Tire

The low-profile tire vs. regular tires debate has been ongoing for the majority of the last few decades. Low-pro tires are stylish, but when we measure tire size possibilities for our vehicles, style is not the only aspect we need to look at.

Tires with a lower aspect ratio will provide better handling, maneuvering, and performance. This is because such tires keep their optimal tire shape and their wider footprints maintain surface contact. Additionally, the larger wheel look creates a sporty aesthetic.

High profile tire vs. low profile tire

On the other hand, a taller aspect ratio will provide more comfort and fuel efficiency. This absorbs the shock of driving and prevents pressure accumulation, making them the perfect touring or highway tires.

However, the average width of a tire is between 185 and 235. This means the average driver will run high-profile tires on their vehicles. Yet, low-profile tires are becoming more and more popular among sports car enthusiasts.

What Is Considered a Low-Profile Tire?

The definition of a low-profile tire has changed over the years. Nowadays, a low-pro tire is a tire made with thinner sidewalls, in other words, lower aspect ratios.

Low Profile Tire Dimensions Made Easy:

For example, if we take two similar tire sizes, but their aspect ratio is the same, the tires will still not have the same sidewall height. There will be a significant difference between a 245/40R17 and a 285/40R17 tire, the latter tire will have a taller sidewall. But, as its footprint is wider, it will be considered a low-profile tire.

Is a Taller Sidewall Better?

While short sidewalls look good and they can offer sharper handling, they come with a trade-off. Low-profile tires experience faster tread wear rates, higher rolling resistance, lesser traction in winter conditions, etc. Compared to this, high-profile tires offer better traction, fuel economy, and comfort levels. They are also able to handle larger loads with ease, depending on the tire type needed.

In other words, tires with a higher aspect ratio are designed for everyday driving, while low-pro tires tend to be the stylish choice.

Tire Aspect Ratio Comparison

Tire aspect ratio comparison infographic

Understanding Tire Size

If you want tire measurements explained, you have come to the right place. At Priority Tire, we wish to provide the information our customers will be able to use. While we have a longer blog post where we explain tire measurements in depth ("Understanding tire size"), let's run through the basics first.

Where is the tire size on a tire? The tire size is located on the tire's sidewall, which consists of three sets of numbers. They are the tire width (the width of the footprint), the height of the sidewall (the height compared to the width in percentages or aspect ratio), and the rim diameter (the size of the rim the tire will fit on).

Tire sizes can also feature letters. P-metric sizes, basically tires for passenger cars and SUVs, will have a "P" before the first numbers. Additionally, if the size has an "R" between the aspect ratio and the rim diameter, then the tire has a radial construction.

Understanding tire measurements - tire size meaning

How to Find Tire Size?

The answer to "Where to find tire size?" is simple. The tire size is located on the sidewall. There is no specific universal placement for the tire size, but the numbers are always big enough to be noticeable.

Furthermore, the vehicle's door jamb will also have a sticker that states which tire sizes will fit the car. If drivers are uncertain of the tire size needed, they can also check the sticker. However, when all else fails, visiting a mechanic and asking for their professional opinion on the tire size measurements is the best option.

Frequently Asked Questions

Can I Use Tires With Different Aspect Ratio?


As long as the difference is not drastic, tire size ratios can be changed without major issues. However, if you wish to significantly change the aspect ratio, figuring out tire size specifications for the tire width and rim diameter needs to be switched as well. This means the tire's height and width need to be optimized.

What Happens if You Put the Wrong Size Tire on a Car?


Not choosing the correct tire width and height will cause problems. It can create problems with the vehicle's speedometer, anti-lock braking system, and stability system. If the tires are bigger to a significant degree, they are at risk of rubbing against the vehicle when turning. This results in premature wear and even vehicle problems.

What Do the Numbers on Tire Size Mean?


The numbers on the tires' sidewall represent tire size measurements. The first number in tire size is the width of the footprint in millimeters. The 2nd number in tire size is the aspect ratio, which number determines tire height represented by the height of the sidewall as a percentage of the width of a tire. Lastly comes the rim diameter of a tire which is shown in inches.

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