The tires have many markings and inscriptions on their sidewall. You have noticed them thousands of times and probably wondered what they mean. Well, these markings might be confusing at first. But, with the help of our article, we hope that this subject will become much clearer for you.
You may think that you don't need to know much about these markings. In the end, go to the store, tell the sales staff what you need and, Probably, they will help you. But our recommendation is to learn to decipher all these markings. This will help you choose the right tire whenever you make an online purchase. Even if you prefer to go to a physical store, the staff is not always trained to offer you exactly what you need.
Tire Size Importance
Choosing the right size of your tire is crucial for your performance and safety on the road. If you choose a tire whose size is not compatible with your vehicle, you will immediately notice changes in traction, stability, and comfort. So, if you want to choose the right size, start by reading the information in your owner's manual. Alternatively, you can see the placard on the driver's door jamb. You will find the manufacturer's recommendation regarding the optimal tire size that is most compatible with your type of vehicle.
Below we will discuss through images everything "tire size" means. The article should help you better understand the size recommended by the manufacturers. Also, you will find out how to correctly switch to other sizes in such a way as not to disrupt performance and safety on the road. So, your sidewall has a lot to tell you. Let's see what it is all about. Before we delve deeper, take a look at the following picture and get familiar with the common tire markings.
Deciphering The Tire Sidewall Markings
All the tires look like in the picture above. Sometimes there may be additional markings that tire makers include at their discretion. Either way, the image above illustrates the mandatory official "code" of tire markings that is required by law. Here is what each of the markings means:
"A" Segment - tire type
This segment refers to the tire type. There are different types of tires and each has a unique symbol. Thus, you can see the following symbols:
ST- stands for Special Trailers. These are usually large and are compatible with travel or utility trailers. ST tires have a rigid construction to cope with additional loads;
LT- refers to Light Truck tires. Their sizes differ from larger to medium, depending on the volume of the truck. Just like the previous type, LT tires are capable of carrying heavy loads so they are optimal for heavy-duty tasks.
P- refers to the passenger tires, as in the case of our example above. These are very different in size and construction, from coupes and sedans to crossovers, SUVs, minivans, and even small pickup trucks.
It is sometimes possible that the tire marking starts with a number, without any letter to indicate the type of tire. Such a tire most probably refers to European size metrics.
Segment "B" - Tire width
The marking on the tire sidewall continues with its width, which calculates how wide the tire is from one side to the other. This margin is measured in millimeters and usually includes a 3-digit number.
"C" segment- tire aspect ratio
This segment indicates the tire Aspect Ratio. It includes a 2-digit number. These 2 numbers refer to the percentage of tire rim height divided by its width. In our case, the tire aspect ratio is 65 (%). This means that the tire's height forms 65% of its width.
As a rule, many drivers look for tires with higher "profiles". For this purpose, they need tires with a higher aspect ratio. The bigger this marking is, the taller the tire sidewall.
"D" segment- tire construction type
This segment is nothing but the construction type of the tire. In our case, we are dealing with a radial tire, hence the abbreviation "R". This type is a replacement for the previous Bias Ply construction. Today, most tires are radial type because this construction is much more optimal. The radial type of tires is much more viable in terms of fuel efficiency and adheres much better to the road.
In addition, this type ensures an increased level of comfort and resists road impacts much better. Also, they have a longer life cycle. All these advantages have gradually removed the type of bias-ply tires, where the radial ones have become the standard of modern tires. Those of the previous generation, i.e. bias-ply, remained valid for a certain category of tires for specialized vehicles. See below the complex construction of a radial tire compared to a bias tire.
"E" segment- diameter
Here we come to the Wheel Diameter. This is a mark in inches and usually consists of a 2-digit number. Some use the term "rim diameter" which means the same thing. This mark measures the distance across the wheel face from one to another bead seat. This is where the wheel and tire meet. In our example, the wheel diameter measures 15 inches.
"F" and "G" segments- Speed and load ratings
In our initial image, segment "F" indicates the Load Index of the tire. Each tire has a certain load limit that it can withstand. Drivers, in turn, must not exceed this limit if they do not want too much stress on their tires. Otherwise, the tires wear out faster and are subject to excess heating, which can lead to a tire blowout.
The "89" number in our example is equivalent to a weight resistance of up to 1,279 pounds.
As for the "G" segment, it refers to the tire's Speed Rating. As in the case of the load rating, each tire is viable up to a certain speed. Manufacturers test each tire category to estimate the speed limit at which it is safe. Having said that, the higher the speed rating, the better the tire performs at high speed. However, we recommend that you maintain a cautious speed, no matter how good your tire is.
The chart below informs you about the load each tire can withstand. Take it into account to avoid exceeding the limits for safety purposes.
How To Choose The Right Tire?
Specialists recommend keeping to the tire size with which your car came from the factory. Car makers fit vehicles with the right tires so that they are maximally compatible with each other. As such, all you have to do is carefully read the markings of your existing tire and choose something similar when it's time to get new tires. Do not forget to take into account the conditions in which you will use the new tires. So, choose wisely between all-season, summer, all-weather, or winter studless or studdable tires.
If, alternatively, you are looking to upsize or downsize your current tires, I am afraid that you will have to consult with a specialist in the field. The thing is that changing tire size might impact your suspension if done incorrectly. So, for safety purposes, consulting an expert is the best way to go to avoid tricky pitfalls. Alternatively, you could see online tire size calculators that would help you to choose a suitable up/downsized tire. Even with this calculator though, confirm compatibility with a specialist before purchasing the tires.
Bottom Line
It is not enough to consider only the tread pattern and tire brand when choosing new tires. You must take into account its size and ratings so that the tire matches your car like a glove. Otherwise, you might severely damage your suspension system and experience poor vehicle performance. Drive safe!