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Getting your car tyre sizes right- a guideline

There are things that human beings take for granted. And one of these is knowing if the tyre size for one’s vehicle is the right size. It may sound irrelevant, but for car owners, this detail is important for various reasons. Tyres carry a huge burden, and so it is important to know if the tyres one owns are the right size for their car. The right size enables a driver to operate the vehicle safely, and maneuver it. It is the tyre size that lends support to a vehicle, enabling it to carry the weight of the car, and its passengers. The tyre size is also what determines the speed of a particular vehicle.

So how then, does one ensure that they get the size of their tyres right?

Every tyre manufactured is labelled with a set of numbers of letters on its surface. For example, the label on your tyre may read 167/ 40 R 12 79H. The 167 represents the tyre’s width in millimeters. The 40 indicates the aspect ratio, which is the tyre height as a percentage of its width. The letter R, stands for radial construction. The number 12 is the diameter of the wheel rim in inches. The next number, 79, is the load index of the tyre; this indicates the maximum weight the tyres can safely hold up. The last letter, H, indicates the maximum speed rating of the tyres. The ratings go from A to Y and go up in increments, with H having a maximum speed of 130.

The markings 167/ 40 R 12 79H are a perfect example of the right tyre size for an ordinary vehicle. Although the markings are not constant and vary from one car to another.

For a car owner, it is a must that they need to own a spare tyre, in case of any damage. There are also situations that call for an individual to change their car tyres. Even in so doing, it is very important that one gets the tyres that have the right size for their vehicle, to prevent problems and accidents.

“If you’re replacing the tyres on your car, make sure that you replace them with those that have the same specifications and ratings. It is also important to make sure that these things match with the original one,” says Anthony Banda, a tyre fitter.

When shopping for new car tyres, one will notice that each tyre has a specific label on it, with different symbols. These symbols are intended to let the individual know how the tyre is rated in the following areas; fuel efficiency; noise; and performance in wet weather.

Fuel efficiency is symbolized by a petrol pump; whereas noise is symbolized by a loudspeaker. A rain cloud on the other hand, is what symbolizes a car’s performances in wet weather. Of course these symbols alone are not enough to let one know if the tyre is right for their car, and as such, there are ratings next to each symbol that communicate how the car performs in each situation.  This labelling is required by law to be there on all new tyres sold. Tyres are rated on a letter system from A to G, with A being the best and G the worst.

One may wonder how these elements are affected by tyre size in any way. It may be wise to note that the fuel efficiency rating that is labelled on tyres denotes the tyre’s tread pattern of the tyres comes from the type of tread pattern that the tyre has. And so, the better the rating, the better mileage the car has.

In the case of noise, the ratings are based on how much noise is heard from the outside, referred to as “drive by” noise. One sound wave signifies best performance, whereas three sound waves show that the tyre just meets the standard regulations.

When it comes to understanding how well a vehicle performs in wet weather, the wet grip is used. This is also indicated on the A to G scale, with A denoting maximum performance of the tyres in wet weather.

And in the words of Tim Shallcross, an advisor to the Institute of Advanced Motorists and former technical advisor to the AA, “it is important for anyone upgrading the wheels and tyres on their vehicle to check the Pitch Circle Diameter (PCD) and the wheel offset”.

He explains that the former is the distance between the holes for the wheel studs and the latter is the distance between the center line of the wheel and the mounting surface of the axle hub.

Despite keeping in mind all the above when figuring out the right tyre size for your car, it is also very important to keep in mind the make and model of the vehicle. In addition, one should also consider what they use their vehicle for, whether it is drives around town, long trips, or for driving off the road.

Other than considerations, one should decide which tyre benefits are most important to them when choosing the right tyre size. Having a specific benefit in mind, combined with knowing how to read and interpret labels on tyres will enable one make the right choice for their car tyre.

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