At first glance, tyres might seem like simple rubber rings, but do not be fooled. Tyres are made using intricate calculations to optimize your driving experience. Making uninformed modifications to your car tyre size can lead to complex issues affecting performance and safety. Among the crucial factors influencing your ride and handling quality is the tyre aspect ratio.

In today’s post we will help you understand the meaning of tyre aspect ratio and how to use a tyre aspect ratio calculation formula when buying new tyres.

What Is Tyre Aspect Ratio?

The tyre aspect ratio is a percentage that represents the height of the tyre's sidewall (the distance from the rim to the tread) in relation to its section width (the width of the tyre from sidewall to sidewall). Essentially, it tells you how "tall" or "low profile" a tyre is.

You can find the aspect ratio represented by the two digits appearing after the slash in the tyre's size code. Here we have a couple of examples to help you understand better.

Example 1: Vredestein Ultrac Vorti 325/35R22

Reading the numbers on the sidewall, we can infer that:

• 325 represents the section width in millimeters (mm).

• 35 is the aspect ratio, meaning the sidewall height is 35% of the section width.

• R indicates a radial construction.

• 22 is the rim diameter in inches.

Example 2: Apollo Aspire 245/40R20

Once again, reading the tyre markings, we can see that,

• 245 represents the section width in millimeters (mm).

• 40 is the aspect ratio, meaning the sidewall height is 40% of the section width.

• R indicates a radial construction.

• 20 is the rim diameter in inches.

Comparison:

The Vredestein Ultrac Vorti 325/35R22 has a wider section width (325mm vs 245mm) and a lower aspect ratio (35 vs 40) compared to the Apollo Aspire 245/40R20. This means the Vredestein has a proportionally shorter sidewall despite being a wider tyre. A lower aspect ratio generally results in sharper handling and a sportier feel but can also lead to a firmer ride. Conversely, a higher aspect ratio like the Apollo's often provides a more comfortable ride but might offer slightly less responsive handling.

Tyre Aspect Ratio Calculator Formula

Tyre aspect ratio is calculated using the tyre aspect ratio calculation formula, which is very simple to understand and implement. You can even use your smartphone’s calculator to find out the correct aspect ratio for your needs.

Tyre Aspect Ratio = (Sidewall Height / Section Width) x 100

Tyre aspect ratio calculations are used by automakers and tyre advisors for installing the best suited tyres for your vehicle.

Use cases for tyre aspect ratio calculation

The tyre aspect ratio is a fundamental piece of information used by various individuals and professionals involved in the automotive industry and beyond. Here's a breakdown of who relies on this crucial specification:

1. Automotive Engineers and Designers:

Engineers consider tyre aspect ratio when designing vehicle platforms, ensuring that wheel wells and suspension systems can accommodate a range of tyre sizes. Aspect ratio also affects the vehicle's overall dynamics and influences the calibration of systems like ABS, traction control, and stability control.

2. Automotive Technicians and Mechanics:

Changes in tyre size or aspect ratio can affect speedometer accuracy, ABS performance, and other vehicle systems. Technicians use this information to diagnose related problems. Modifications to wheel size or aspect ratio may necessitate adjustments to vehicle alignment and suspension settings. Technicians use aspect ratio information to ensure that new tyres fit correctly on the vehicle, considering factors like clearance and load capacity.

3. Tyre Manufacturers and Engineers:

Tyre aspect ratio is a key design parameter impacting a tyre's performance characteristics, including its handling, comfort, and load capacity. Manufacturers tailor the tyre aspect ratio to meet the requirements of different vehicle types and intended uses.

4. Motorsport Professionals:

In motorsport, adjusting the tyre aspect ratio is a common way to fine-tune a vehicle's handling characteristics and adapt to different track conditions. Different racing disciplines require tyres with varying aspect ratios to optimize performance for factors like grip, speed, and durability.

5. Vehicle Owners:

Enthusiasts looking to modify their vehicle's look may change wheel sizes and consequently need to adjust the aspect ratio of a tyre to maintain the proper overall diameter and achieve the desired aesthetic. As discussed earlier, understanding aspect ratio is vital for selecting tyres that match your desired ride comfort, handling performance, and vehicle's specifications.

6. Apollo Vredestein Sales Staff:

Professional sales staff at Apollo Vredestein tyre shops rely on their understanding of tyre aspect ratio to guide customers towards tyres that meet their needs and preferences.

How Can You Use Tyre Aspect Ratio Calculations When Buying New Tyres?

The sidewall height, derived from the tyre aspect ratio, is a critical factor to consider when choosing new tyres. It directly influences your vehicle's ride comfort, handling characteristics, and even aesthetic appeal. Here's how to use sidewall height as an indicator:

1. Ride Comfort:

A taller sidewall provides more cushioning, effectively absorbing bumps and road imperfections. This translates to a smoother and more comfortable ride, especially on rough roads. It's often preferred for SUVs, sedans, and vehicles focused on comfort.

Lower sidewall height (smaller aspect ratio): A shorter sidewall offers less cushioning, resulting in a firmer ride. While you'll feel more of the road, this setup enhances responsiveness and provides a sportier feel, commonly favored for performance cars.

2. Handling and Performance:

While comfortable, taller sidewalls can flex more during cornering, potentially leading to less precise handling and a feeling of “roll." The reduced flex of a shorter sidewall improves steering response and cornering stability, contributing to a more dynamic driving experience.

3. Appearance:

Tyres with larger sidewalls tend to have a more traditional and robust look while tyres with shorter sidewalls often create a more sporty and modern aesthetic, with a "low-profile" appearance.

4. Load Capacity and Towing:

Generally, tyres with larger sidewalls offer a higher load capacity, making them suitable for heavier vehicles or those used for towing. Whereas, tyres with lower sidewalls are not suited for such heavy duty applications and may fail if pushed to their limits.

5. Matching to Wheel Size and Vehicle Requirements:

Maintaining the original overall diameter of your tyres is crucial for accurate speedometer readings and proper vehicle functioning. When changing wheel sizes, you may need to adjust the tyre aspect ratio to maintain the correct diameter. Always consult your vehicle's manual or a tyre professional to determine the appropriate tyre size and aspect ratio for your specific vehicle.

Using the Tyre Aspect Ratio Formula to Find the Sidewall Height

A simple mathematical reverse engineering of the tyre aspect ratio calculator formula can help you find the height of your tyre sidewalls. Here’s how,

Sidewall Height = (Tyre Aspect Ratio / 100) x Section Width

Using this formula, we can check the sidewall height of the Vredestein Ultrac Vorti and (35/100 x 325mm = 113.75mm) and the Apollo Aspire 4G Plus (40/100 x 245mm = 98mm) and see that while the Aspire has the shorter sidewall height, it’s also proportionately thinner than the Vredestein, which makes it better suited for luxury sedans where comfort is a priority. On the other hand, the Ultrac Vorti mixes performance with style, and can be a great choice for a sportier high performance car.

Finding the Best Tyres for Your Car

Understanding the aspect ratio of a tyre and how to calculate it using the tyre aspect ratio calculation formula empowers you to make informed choices. However, to ensure you find the perfect tyres with the correct aspect ratio to match your specific vehicle and driving needs, expert guidance is invaluable.

For personalized assistance and recommendations, we encourage you to visit your nearest tyre shop and consult with an Apollo Vredestein representative. Our tyre experts can help you navigate the various options and select the tyres best suited for your car.

Alternatively, you can connect with our helpful team directly by calling our helpline number, 1800 212 7070.