Tire size and correct selection for the car. How to decipher the marking?

Usually the numeric string for the tire size is expressed as XXX/XX RXX. In this case, X stands for specific numbers, and R is the diameter of the rim, expressed in inches. The problem is that the correct wheels are not always installed on the hubs and they differ from those recommended by the manufacturer. So what do you need to know about tire sizes? Read our text and find out how to fit tires to your car.

What tire size to choose for your car?

Preferably the one on which the car left the factory. Tire size is chosen not only for aesthetic reasons, but also for safety, running and structural properties. Riding on very large rims with low profile tires is extremely popular these days. Often these elements are finalized at the first stage of car tuning by juvenile (and not only) drivers. What are the effects?

Why Choose Factory Tire Sizes?

Larger rims require a lower tire profile. Otherwise, the wheel will not fit into the wheel arch and may rub against the dimpled MacPherson struts. In the rear, on the other hand, the tapping of the suspension can cause the tread to rub against the wheel arch. In addition, driving on very thin tires transmits more vibrations and vibrations to the suspension and interior of the car. This results in faster wear:

• rubber suspension elements;
• steering rod ends;
• stabilizers;
• joints. 

It also means less driving comfort, so choose a standard tire size.

Tire size - what does it mean?

Turning to the mysterious symbol at the beginning of the article, it would be good to decipher it. What does XXX/XX RXX mean?

The first 3 digits are the tread width. So the tire size starts from the width of the tire mounted on the rim (expressed in millimeters). Typically, for city cars, these are values ​​​​in the range of 175-195. Importantly, they change every 5 millimeters. So you won't find a 182 tire.

What does tire size mean - profile height

The next parameter is the profile (XX after the slash). It is expressed not in millimeters, but as a percentage. It strictly refers to the tread width, so it follows the slash. So let's assume your car's tire size is 195/70. This means that the tread width is 195 millimeters and the profile height is 70% of the tread value. Simple calculations will give 136 millimeters. Enough. 

The last tire size designation, i.e. rim diameter

There is another designation preceded by the letter R. This is, of course, the diameter of the rim in inches, i.e. the distance between the rims of the tire itself. In practice, it shows which rim should be put on the tires.

How to check tire size on a car?

If you want to quickly find out the size of a tire, just look at its profile. You should be able to easily find the string of numbers on it that we just deciphered. It is clear that besides him there are other traces on the tires. This is due to the fact that in addition to the dimensions of the tire, they have a lot of other features that should be considered before buying. But back to size. What to do if you have a reasonable suspicion that the previous owner did not choose the right tire size for the car?

What tire size to choose, i.e. checking for valid values

There are several ways to find information you can trust. First, look for the nameplate posted by the manufacturer. You may notice this:

• from the driver's door on the passenger side;
• on the gas tank hatch;
• on one of the vehicle's support legs. 

The tire size, together with the inflation level of each wheel, must be indicated on such a sticker or on a riveted tin plate.

What tires for the car - we are looking further

If the badge we mentioned in the previous paragraph is not on your car, don't worry. There are other ways out. One of them is to search the discussion forum about the brand. You can easily find there not only the factory values ​​for the car, but also all other equipment that can be installed on your car. Another option is to use calculators where you enter the year and version of the model.

Tire size and additional markings - do they matter?

Tire and rim size in general is important when mounting a wheel, but is also important when driving. There are other parameters that affect the way you drive and the safety of you and other road users. This includes, among other things, the load and speed index. These values ​​are usually placed immediately after the tire size. They consist of two or three numbers and a letter (eg 91H). What do these parameters say?

Load and speed index

The first of these, that is, the load index, informs the driver about what the maximum load on a given tire can be when reaching maximum speed. Unfortunately, special tables with values ​​are needed to solve the puzzle. 91 in this case means 615 kilograms. Impossible to guess. H is the speed index. In our example, this means that the tire speed must not exceed 210 km/h.

How about custom sizes?

Of course, there are many drivers who fit wheels of other sizes than those recommended by the manufacturer on their cars. However, they do not experience the excessive side effects described at the beginning of the article. So how do you choose a custom tire size to get it right? It is best to use online calculators. Based on a specific vehicle, they show how small and large discs can be installed on a given model without changing suspension components. Then you can also pick up wide and high tires for such disks.

How about tire size? For some, what the manufacturer says is just a suggestion. Others, on the contrary, cling to the factory settings. In principle, neither one nor the other group can be surprised by anything. Remember, though, that design isn't everything, and the tire is the only contact between the car and the surface. When choosing them, consider not only the size. Also pay attention to their quality.