From load indices to speed rating, construction to the aspect ratio, there is indeed a plethora of tyre terminology that comes together to paint a picture of a tyre's abilities and suitability.
We've put up this handy guide to help you understand tyre marks. Want to quickly determine the physical dimensions of your tyre? Use our 'Find Your Tyres' feature on Firestone Tyres Birmingham to find the right tyres for you.
Are Tyre Marks Necessary?
Tyres are amongst the most critical components of your car when it pertains to remaining safe at all times. They are in the heart of the action, whether you're steering, braking, or drifting along. After all, it's the only piece of your car that makes contact with the ground. As a result, when it refers to tyre replacement, it's critical that you get it correctly.
Let's talk about tyre marks. These determine the dimensions and physical characteristics of a tyre to select a replacement that fits your car. While some of these tyre markings are insignificant, the majority have a considerable impact on the performance and security - so getting them properly is critical.
While tyres appear to be nothing more than circles of rubber, each is unique. As a result, it's critical that you double-check your tyre labels before making any reservations. Failure to do so may result in the purchase of tyres that are unsuitable for the vehicle and hence cannot be installed.
Where Can You Find Tyre Markings?
It should go without saying that tyre labels are engraved onto the sidewall of a tyre. What you may not realise is that you can obtain information about your manufacturer-recommended tyres in some other places as well, including:
- The owner's manual for the vehicle
- Fuel cap
- Inside the glove box's door
- The doorjamb of the driver
You must keep in mind that the sidewall of the tyre only shows the requirements for that specific tyre. To ensure that a tyre is suitable for your vehicle, examine your owner's manual or one of the sources listed above. You can also contact the Tyres team if you have any questions.
The Method To Understand Sidewall Markings On Your Tyre
The sidewall of a tyre contains information about the tyre. We will start with the size code, which is represented by a series of letters and numbers.
Let's look at an example: 18 95 H 225/55 R
- Sidewall decals
- Width of a tyre
- Profile or aspect ratio
- Tyre manufacturing
- Inch diameter of the rim
- The Load Index
- Index of speed rating
Tyre Diameter
"225" is the number in the sequence. This is the width of the tyre in millimetres, analysed from sidewall to sidewall.
Aspect Ratio
The aspect ratio – or assessment of the sidewall height – is represented by the next two integers ("55"). (in mm). This is really the ratio of the cross-section to the diameter of the tyre. In the above instance, a tyre with a ratio of 55 will have a height equivalent to 55% of its width.
Tyre Manufacturing
Following that is a letter which explains how a tyre is made. The "R" implies that the tyre is radial in manufacture. That's where the inner ply cords run radially around the case from bead to bead. Diagonal or biased ply, denoted by the letter "D," is a less common tyre structure.
Inch Diameter of the Rim
The next number represents the diameter code. This, unlike the width, is displayed in inches. This is significant since it indicates the width of the rim. The number "18" in the preceding example indicates that the tyre must be matched to an 18-inch rim wheel.
The Load Index
The load rating is found after the rim width. When a passenger automobile tyre is filled to its maximum recommended pressure, this informs you of its full capacity. In this case, the figure (in this case, "95") corresponds to the index instead of the weight. As a result, you must reference a load index table to determine the load in kg for every rating. For a load index of "95," the maximum load weight per tyre is 690kg.
Index of Speed Rating
As you might expect, this is the top speed a tyre can maintain when properly inflated and loaded. This letter, like the load index, refers to a look-up database that shows the maximum allowable pace of a tyre. In this case, "H" indicates that the car has a top speed of 130 mph when fully loaded.
You can find the above information on the Tyres Birmingham website. For any assistance give them a call.
