What You Need to Know About Various Sizes of Car Tyres

You possibly end up more confused when looking for the right size of car tyres. Fact is you are not alone in this matter as many other individuals go through the same issues. What does the R mean? What is Radial or Cross ply? Which is the best tyre for driving on snow or mud? Don’t worry because your local tyre dealer on the same par as gilnahirktyres.co.uk will be able to help you out if you get stuck.

It is always good to know why things are the way they are and so here is all the information you will need as follows…

These are only a few of the many questions people ask. In order to get good service from your car, it is important to always fit the right tyre. This is usually determined by the car manufacturer recommendation, type of terrain, nature of use, load capacity and much more. So what does a vehicle tyre that is marked P215/65 R15 on the sidewall mean?

Car Tyre Size P215/65 R15 Explained

  • P – Metric

Metric generally indicates what category of vehicles the tyre is suited for. US made tyres feature the letter at the beginning while European tyres don’t have the number. In the case above the P stands for passenger vehicles. Another metric symbol is LT which means suitable for Light Trucks.

Tyres marked for light trucks require higher inflation pressure than passenger tyres due to carrying heavier loads. The metric values for European and American tyres aren’t the same hence a buyer should familiarize with then metrics before buying.

  • 215 -Tire Width

215 basically stand for 215 millimeters and is the distance between one sidewall to the other. The higher the number the wider the tyre, for, example there is 185, 210, 215,220, 225, and more. A wide tyre means that it offers more traction and grip on the road. It is also more effective on slippery situations such as snow, mud or rain especially if the inflation pressure has been reduced.

  • 65 – Aspect Ratio/Height

In our example, there is a number 65 after the forward slash. This is referred to as the tyre aspect ratio and basically compares the tyres height to its width. In our case, the tyre has an aspect ratio of 65 meaning that it accounts for 65% of the width of the tyre. 65% aspect ratio means the height of the tyre is 139.75mm (0.65 x 215). A large tyre ratio means that the tire’s sidewall is also bigger. Low profile car tyres which are mainly used in racing or high performance have a small aspect ratio.

  • R – Radial

Radial indicates the nature or construction of tyre. Tyres are manufactured using different techniques and the most common design is radial, cross ply (bias), belted bias and solid. Radial indicates that the layers used to make the tyre run radially. This type of tyre is the most common especially in private and light commercial vehicles. Other types such as cross ply/ bias, belted bias, and solid are usually used for heavy commercial applications.

  • 15 – Wheel Diameter

15 is the diameter of the car tyre and is measured in inches. This measurement is what people are most familiar with. It is the halfway distance from one end of the inner opening of the tyre to the other end. Or in simpler terms it indicates the correct size of car rim that will fit into the tyre. Diameters range from 13 to 22 inches.

A lower number means the rim is also small. Passenger vehicles are fitted with small rims such as 13, 14, and 15. SUVs, vans and light trucks can accommodate 16, 17, and 18 inches, while large vehicles are fitted with rims of 22 inches and above.

Other Important Notes about Car Tyres

When choosing the right tyres for your vehicle there are other issues of concern. These include the following:

-Load Index: This index is indicated on the sidewall of the tyre in either pounds or kilograms. It guides the user on the maximum recommended load the tyre can safely carry when properly inflated. For instance, a tyre marked 91 should not carry more than 615 kgs. Exceeding the limit may cause the tyre to burst prematurely or accelerate tear and wear.

-Speed Rating: The maximum speed at which the tyre should run is also indicated on the sidewall using alphabetical letters. For example, a tyre labeled H has a top speed of 210km/h or 130 mph. V-rated tyres have a capacity to attain a top speed of 149 mph or 240km/h. NB: It is critical to stick within safe and recommended speed limits.

-Traction Grade: This measures how well the tyre grips the surface especially during wet conditions. Good grip improves road handling as well as safe braking. The grades comprise of AA, A, B, and C, with AA offering the best traction in wet surfaces.

-Temperature grades: car tyres are also marked with temperature grade that indicates the temperatures the tyre can withstand. A tyre that can withstand high temperature can also operate at higher speeds and in extreme conditions such as desert. Grade A can run in speeds exceeding 115 mph, B is suitable for between 100 and 115 mph, while C is effective for between 85 and 100 mph.

The above are some of the things that are indicated by the tyre size marked on the sidewall. Although the numbers may appear basic, they play a vital role in improving drivability and ensuring you stay safe. When choosing car tyres always pay attention to the tyre size and stick to the car as well as tyre manufacturer’s recommendations.


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