Understanding Tyre Sizes in South Africa: A Comprehensive Guide for Drivers

Learn how to read and find your tyre size with our detailed guide tailored for South African drivers. Discover everything from metric to flotation tyre sizes, ensuring you choose the perfect tyres for your vehicle.

Knowing your tyre size is essential for every driver, but the numbers and symbols can often be confusing. Without understanding the correct tyre size for your vehicle, purchasing new tyres can become an unnecessarily challenging task.

To make sense of tyre size numbers, it's important to consider the different types of tyres that manufacturers produce. The combination of metric and numeric tyre size formats can add to the confusion. However, whether you're looking at tyres for a passenger vehicle or light truck (LT), a clear understanding of tyre sizes can simplify the selection process.

In this guide, we'll explore where to find your tyre size and how to interpret the numbers, ensuring you choose the right tyres for your vehicle in South Africa.

Where to Find Your Tyre Size

Locating the tyre size for your vehicle is straightforward, and there are several methods to do so. Vehicle manufacturers make it easy by placing tyre size information in various locations on the car.

Here are the most common places to find your tyre size:

- Owner’s Manual: Your vehicle’s owner’s manual lists the recommended tyre sizes, and may also provide suitable alternative sizes.

- Driver-Side Door (Jamb): Car manufacturers typically place a sticker on the driver-side door or door jamb that displays the original equipment (OE) tyre size.

- Glove Box Door: You may find another tyre size sticker on the inside of the glove box.

- Fuel Tank Hatch: The inside of the fuel tank hatch often has a smaller sticker showing the OE tyre size.

- Current Tyres: The most reliable way to check your tyre size is by looking at the sidewall of your current tyres. If the original tyres have been replaced with different sizes, the OEM tyre size might no longer apply.

How to Read Tyre Size Numbers

Finding where the tyre size is listed on your vehicle is just the first step. Understanding how to read these numbers is crucial before purchasing a new set of tyres.

Deciphering tyre size numbers can be tricky, as not everything is straightforward. Knowing how to accurately read tyre sizes is essential to ensure you select the right tyres for your vehicle.

Let's break down what tyre size means for both metric and flotation numeric tyres.

Metric Tyre Sizes

Whether you need tyres for a passenger vehicle or a light truck, metric tyre sizes are commonly used to specify the dimensions. These sizes are found on a wide range of tyres, including those for touring, performance, highway, and even some off-road applications, making them the most prevalent on South African roads.

Here’s a detailed explanation of metric tyre sizes:

Prefix Letters

Before the actual tyre size, manufacturers use letters to indicate the type of vehicle the tyre is designed for. Common prefixes include:

 - “P” for passenger cars, SUVs, crossovers, and electric vehicles.

 - “LT” for light trucks.

 - “ST” for specialty trailers.

Some tyres may also feature a “C” at the end of the size, indicating that they are designed for commercial vans.

Tyre Width:

The first number in the tyre size refers to the tyre's width in millimeters, measured from sidewall to sidewall. For example, in a tyre size of 205/55R16, the tyre’s width is 205 millimeters.

Aspect Ratio:

The middle number represents the aspect ratio, or the tyre sidewall height, expressed as a percentage of the tyre's width. For instance, in a 205/55R16 tyre, the aspect ratio is 55%, meaning the sidewall height is 55% of the tyre's width.

Construction Type:

The letter following the aspect ratio indicates the tyre's construction. Common types include:

 “R” for radial construction, which is the most common.

 “D” for diagonal or bias-ply construction.

 - A hyphen (-) signifies a bias-ply tyre without a radial structure.

If the tyre size includes “ZR,” it signifies a high-performance radial tyre capable of speeds of 240 km/h or more.

Diameter:

The last number in the tyre size is the diameter of the wheel in inches, which indicates the size of the rim the tyre will fit. While the width and aspect ratio can be adjusted slightly, the rim diameter must match exactly.

Flotation or Numeric Tyre Sizing

Flotation tyres are often used for specialty vehicles such as ATVs or tractors, but they are also common in off-road and commercial truck tyres. These tyres have a wider footprint, requiring broader wheels, which makes them ideal for navigating rough off-road terrains.

Flotation tyre sizes are measured in inches.

Here’s how to interpret flotation tyre sizes:

Tyre Height:

The first number indicates the overall tyre height or diameter. For example, in a 35x12.50R17 tyre, the tyre height is 35 inches.

Tyre Width:

Unlike metric tyres, the middle number in flotation sizes represents the tyre's width from sidewall to sidewall, rather than the tread width. In the 35x12.50R17 size, the tyre is 12.50 inches wide.

Construction:

 Similar to metric tyres, flotation tyres can be either radial or bias-ply in construction. An “R” after the width denotes a radial tyre, while a hyphen indicates a bias-ply tyre. For instance, 35x12.50R17 tyres are radial, while 35x12.50-17 tyres are bias-ply.

Rim Diameter:

The final number represents the rim diameter in inches, specifying the wheel size the tyre is designed to fit.

Comparing Flotation and Metric Tyre Sizes

Converting between flotation and metric tyre sizes is sometimes necessary, as the formats differ not only in how they are written but also in the units of measurement. Below is a handy chart that shows the most common conversions between flotation and metric sizes.

Load and Speed Ratings

Tyre size markings also include important information about load and speed ratings, which are found after the tyre size on the sidewall. These ratings indicate the tyre’s maximum load capacity and speed capability.

Load Index:

The load index is a numerical value that reflects the maximum load a tyre can carry. For most passenger cars, this value ranges between 75 and 100, while SUVs and trucks typically have a load index above 100. For metric light truck tyres, you may find two load ratings.

Speed Rating:

The speed rating is represented by a letter that indicates the tyre’s maximum speed capability. These letters range from A1 to ZR, with each corresponding to a specific speed range. The letter “H” is an exception to the alphabetical order. The speed rating is determined based on the tyre’s performance characteristics.

Frequently Asked Questions

1. What Do the Tyre Size Numbers Mean?

Each part of the tyre size number corresponds to a different dimension: the first number is the tyre width in millimeters, the second number is the sidewall height as a percentage of the width, and the last number is the rim diameter in inches.

2. How Can I Check My Tyre Size?

You can check your tyre size by looking at the sidewall of your current tyres. If your vehicle’s tyres have been replaced with a different size, the owner's manual or stickers inside the car may no longer provide accurate information.

3. Where Can I Find My Tyre Size?

Tyre size information can be found in several places: the owner’s manual, a sticker on the driver-side door or door jamb, inside the glove box, or the fuel tank hatch.

--

Shop Tyres by Size

For the best prices on high-quality tyres, explore our wide selection at Malas. Find the perfect fit for your vehicle today!