Car tyres seem to be the simplest parts of a car that people should know about but not many people know the exact sizes of the tyres they have on their cars and whether it’s the right type for their vehicle.
The knowledge of a lot of people when it comes to tyres is restricted to the diameter of their wheels, such as 15 inches, 16 inches, 17 inches etc.
The exact size of your tyre and the meanings of all the numbers written on them also matter as certain automobiles that come with high performance suspensions have different tyre requirements for the front and back wheels of the vehicle respectively.
Finding out the size of your tyres is a simple task as you can see the information you need written on the sidewall of your tyre with newer vehicles having it written somewhere around the drivers door.
What The Number And Letters Mean
If for instance, you drive a 2008 Toyota Sienna, the equipment tyr on the space bus should be a P215/70R15. The “P” represents passenger tyre, the 215 is the section width of the tyre in millimeters, where the sidewall of the tire bulges at it’s widest point and 70 represents what is known as the aspect ratio or the percentage of sidewall height to section width.
This means the sidewall is 70% as tall as the tire is wide. R stands for radial and 15 represents the diameter of the wheel.
Also, when the letters “M + S” is written on your sidewall, it usually indicates the tyre’s tread design makes it suitable for mud and snow. A tyre with “LT” written in place of ‘P’ means that the tyre is suitable for a light truck.
Low Profile Tyres
These are tyres that have the sidewall height to section width (aspect ratio) lower than 70 percent. The smaller the aspect ratio, the shorter the side wall of the tyre resulting in what is referred to as a low profile tyre. Any tyre with an aspect ratio of 40 and below has a short profile and those of 70 and above are tall tyres.
Speed Ratings And Load Carrying Capacity
Some other important information that you should be conversant of is the speed ratings and load carrying capacity of your tyres. For example, a 2015 Chevrolet Corvette comes with P245/40ZR18 (93Y) tires on the front and P285/35ZR19 (99Y) tyres on the rear.
The letter Z in the tyre size tells the speed rating of the tyres and that it can withstand speeds that’s exceed 151 miles per hour.
The numbers 93 and 99 on the other hand signifies the load carrying capacity of the tyres.
Here is a list of likely speed ratings and load carrying capacity ratings you are likely to see.
Speed Ratings and Load Carrying Capacity
M- Up to 81 mph
N- Up to 87 mph
P- Up to 93 mph
Q- Up to 99 mph
R- Up to 106 mph
S- Up to 112 mph
T- Up to 118 mph
H- Up to 130 mph
V- Up to 149 mph
W- Up to 168 mph
Y- Up to 186 mph
Z- Up to 151 mph
The most important thing when it comes to speed ratings and load carrying capacity is to use the exact tyres your vehicle needs to maintain the speed and load the vehicle is designed for. Using the wrong tyres could be fatal, which is why you should get the right information before replacing the tyres of your vehicles.