Minimum disk width. Tire calculator online. Tire calculator - size comparison

Tires made in America and Europe have different markings. A situation often arises when it is necessary to convert inches to centimeters. In this article we will describe ways to decipher tire sizes in centimeters.

Tire marking in metric system

The main dimensions of tires are indicated by markings, these include:

1. Tire profile width is the distance, expressed in millimeters or inches, between the outer sides of the sidewalls of an inflated tire, without taking into account elevations, trim or belts. The specified value should not be more than 30% greater than the width of the rim of the product.
2. Series of tires. Indicates the ratio of the width and height of the product profile. Allows you to distinguish rubber in this way:

• low profile - series less than 70%;
• high profile - in the range of 70-82%;
• full profile - more than 85%.

1. Tire design. There are radial and diagonal tires. In the first case, the fibers of the cord layer are placed perpendicular to the circumference of the wheel. In the second option, the cord threads are overlapped. Radial tire design is more common; such tires provide better traction between the wheels and the road surface, and they are more reliable during operation.
2. Wheel radius.

How to understand what tire markings mean? Markings on the side car tires applied by tire manufacturers. Factory markings are in metric or inch units. For example, the size of tires marked in the metric system 265/75 R15 corresponds to the designation of the inch system 31 × 10.5 R15. The decoding of these symbols in centimeters means:

1. The designation 265/75 R15 indicates the tire sizes:

• 265 is a number that determines the width of the tire (one centimeter is equal to ten millimeters, 265 mm = 26.5 cm);
• 75 is a percentage (75%) that determines the relationship between the tire profile height and the tire width (265 * 0.75 = 198.8 mm or 19.9 cm), the found number indicates the tire profile height;
• R - denotes radial tire type;
• 15 - wheel diameter, the size is indicated in inches, you can convert the specified parameter to centimeters by multiplying the digital value of interest by 2.54, since 1 inch is equal to 2.54 cm, in the end we get 15 * 2.54 = 38.1.

1. The designation 31×10.5 R15 stands for:

• 31 - wheel height (31 inches or 31*2.54=78.7 cm);
• 10.5 - tire width (10.5 inches or 10.5 * 2.54 = 26.7 cm);
• R - indicates the radial type of tire;
• 15 - determines the diameter of the wheel (15 inches or 15*2.54=38.1 cm).

• subtract its radius from the total height of the tire (78.7-38.1=40.6 cm);
• divide the resulting value by 2 (40.6/2=20.3 cm).

Differences in tire markings

When deciphering tire sizes, pay attention to the letter in front of the tire dimensions:

1. “P” - indicates the “P-metric” system, used for minivans, light pickups (with a load capacity of up to 0.5 tons). This system is very convenient; it is often used by tire manufacturers.
2. “T” - the indicated letter marks “spare” tires: the rubber can be used until the main tire is repaired or replaced.
3. “LT” stands for the Light Truck-metric system, designed for trucks and vehicles capable of transporting large loads. This category includes vehicles with a carrying capacity of up to 1 ton.
4. “ST” - indicates “Special Trailer Service”, the products are designed for caravans and can also be used to transport boats or cars.

Letter values ​​may appear at the end of tire markings, in which case they mean:

1. “LT” - the tire refers to products with early markings:

• “Numeric” - numeric, tires are designed for vehicles transporting heavy loads, trailed trailers
• “Wide Base” - tires with a wide base; manufacturers produce such products with a rim diameter of 16.5 inches;
• “Flotation” - flotation, large-sized tires that allow the car to move on a sandy surface or mud.

1. “C” - tires for commercial use, suitable for vans and delivery vehicles capable of transporting large loads.

If at the beginning of the marking there is no letter designation and a three-digit number, for example, 45R15, then this is a tire with a metric size of the Euro-metric system, applicable on tires from European manufacturers. The indicated dimension corresponds to the decoding according to the “P-metric” system, but is characterized by lower loads.

• 235 - product width (235 mm = 23.5 cm);
• 710 - a number indicating the outer diameter of tires (710 mm = 71.0 cm);
• 460 - tire rim diameter (460 mm=46 cm);
• A - designation of asymmetrical rubber beads, for example, 460A means that the outer bead has a diameter of 45 cm, and the inner one has a diameter of 47 cm.

This non-standard marking is designed for cars with wheels of a specific size, which differ in side profiles from standard metric or inch products. When faced with non-standard markings, it is better to find out their decoding from the tire manufacturer.

Comparison of calculated data

Independent decoding of tire sizes requires a certain accuracy of calculations. You can check whether the conversion from centimeters to inches and vice versa is correct using tire calculators. With their help, you can also find out how many tire sizes are suitable for a particular car model.

Tire calculators are easy to find on the Internet; they usually have American and European sizing systems at the same time. Therefore, by entering the tire sizes recommended by the car manufacturer in the metric system, it is possible to obtain a list of American and European tires. This is very convenient, if necessary, select the brand of tires you are interested in, and also view the possibility of changing the tire sizes recommended by the manufacturer. When using tire calculators, it is necessary to take into account the error arising from rounding, so it is better to translate the dimensions of interest manually, then check them with the options calculated by the Internet resource.

Conclusion

American markings rubber, if you do not take into account the unusual inches, is very convenient to use. But in most situations you have to deal with the metric notation system. Converting inch dimensions to centimeters is not difficult if you understand the decoding of the designations applied by manufacturers to lateral surface car tires In this case, it is necessary to take into account the error in calculations, which may arise due to inattention or rounding of the obtained values. To correctly calculate the dimensions, it is better to use manually, then compare the obtained parameters with the data of tire calculators. We do not recommend using only one method, since the embedded electronic computer programs also contain a certain rounding error.

Using a tire calculator you can easily calculate how the following will change: the external dimensions of the wheel, the height ground clearance(clearance), speedometer readings and other characteristics when installing tires of a different size on your car. The calculator calculates all tire sizes in millimeters, and vehicle speed in km/h.
The calculator will also help you calculate the required rim width for a certain tire size.

How to use the tire calculator:

First enter the standard size installed on your car, and then the one you want to install and click “calculate”. The table on the right will show the results of the calculator's calculations.
Detailed information about tire markings in the section: tire markings.

We recommend that you install only the factory tire sizes that are listed in the owner's manual for your vehicle. Installing non-standard sizes may void the dealer's warranty, as well as degrade vehicle performance and handling.

Tire calculator for European tires

Old size:

New size:

145 155 165 175 185 195 205 215 225 235 245 255 265 275 285 295 305 315 325

/ 25 30 35 40 45 50 55 60 65 70 75 80 85

12 13 14 15 16 17 18 19 20 21 22 23 24

Found in the directory:

175/70 R13 -

175/70 R13 -

When converting tire sizes using a calculator, keep in mind that:

With increasing diameter wheel rim, (and, as a consequence, reducing the height of the tire profile so that the outer diameter of the wheel remains unchanged) increases the load on the car’s suspension, and comfort also worsens (the car will become noticeably stiffer).

If the tire profile increases excessively, the car becomes “rolly”, handles worse, and at critical values ​​of the profile height, the tire may begin to cling to parts of the car body and suspension, which will subsequently lead to its destruction.

It’s always better to purchase complete wheels right away, but if you suddenly had to start selecting tires based on rims, then don’t worry, now we’ll study all the features of this process so that even an inexperienced person can handle it.

Main parameters and their designation

First you need to familiarize yourself with the main parameters and their designation. The wheel diameter is designated by the symbol “D” and is considered the most significant characteristic. It is very important to follow the dimensions recommended by the manufacturer. An increased diameter will distort the speedometer readings. It is also possible for the wheel to rub elements of the body and chassis.

The diameter of the rims is designated “dd”, but their width (the distance between the inner edges of the rim) is “Wd”, and is usually indicated in the markings in inches. Height also matters; this characteristic has the code “dt”. Low profile tires wear out faster and are not suitable for all roads. If the condition of the road surface is not ideal, then it is better not to buy such tires, since in this case the load on the suspension increases and there is a possibility of disc deformation. In addition, they are noisier.

“Wt” – tire width. Wide tires are better suited for driving on dry roads, as this reduces braking distance. For urban conditions and slippery roads It is recommended to use narrow tires.

Before we talk directly about the selection of tires on rims, we should understand a little about the markings of one and the other. Let's start with the disks. The marking can be stamped anywhere except the inner surface facing the rim. To make it easier to understand, let's look at decoding using a specific example.

Let's say you found the following code "6.5JJx13FH6x98ET20d62.1". The first is the width of the disk and it is indicated in inches, in our case it is 5.5. to convert this value to millimeters, multiply it by 25.4. This is followed by a Latin letter (P,D,B,K,J) or a combination of them (JJ, JK). This symbol characterizes the shape of the profile contour, the height of the shelves, their angle of inclination and the radius of curvature. “JJ” indicates that the car is all-wheel drive.

If for letter designations If you see the “x” symbol, this means that the disk has a one-piece design, but collapsible copies have a “-” sign in the marking. Next, the diameter of the discs is indicated, followed by the humps index. This is the value indicating the annular projections along the edges. They have a very important function - fixing tubeless tires during turns. A simple hump is designated by one letter “H”, a flat one, as in our case, is “FH”, and an asymmetrical one is “AH”. There are designs that do not have humps.

The following indicates the value to be paid special attention when selecting tires for wheels, this is the location of the mounting holes, in our case “6x98”. This means that there are 6 of them, and the diameter of the circle is 98 mm. The number of holes ranges from 4 to 6, and the circumference can range from 98 to 137.9 mm. The following indicates the distance between the plane of attachment of the disk to the hub and its vertical axis. This parameter is called disc offset and is indicated by the combination of letters “ET”. The number following them indicates the offset value in millimeters, in our case it is 20 mm.

The offset can be positive, zero or negative. The suspension and steering mechanism are adjusted depending on this parameter. The last thing in the marking is the diameter of the mounting hole. For passenger cars this value ranges from 50 to 70 mm. Quite often the maximum load, production date and production method are also specified. Discs are produced forged, cast and stamped.

Tire markings

If you decide to select tires based on the width of the rims, then you definitely need to be able to decipher the tire markings. After all, this code contains all the necessary information. You can find it on the side surface of the tire. However, it indicates a lot of other information about the tires, starting from the country of manufacture, model and ending with purpose and type. This information, of course, is of great importance, as it affects the quality of the product, but if we are talking about selecting tires for certain wheels, then they do not play a decisive role.

But the most important information contained in code called a type. To make it as clear as possible, let's look at the decoding using a specific example. Let’s say you found the following code “225/50 R14” on the side of the tire. The first number indicates the profile width in millimeters. Moreover, measurements are made taking into account the sidewalls. Next comes the height value, expressed as a percentage relative to the width. For us it is 50%, which means that to arrive at the size in millimeters, you need 225x50%, which turns out to be 112.5 mm.

The following symbol gives information about the construction of the cord. "R" means the tire has a radial cord. And the number following it expresses the mounting size of the rim; it is indicated in inches. As a matter of fact, this is the most important information that is needed when selecting tires by size. The marking also contains a column with speed and load indices. There are many tables on the Internet in which these numerical and alphabetic designations are translated into specific values ​​of loads and speeds.

What will help you choose the right tires?

Choosing tires is a very responsible task, because if you put inappropriate tires on your car, technical specifications tires, then problems cannot be avoided. This could be incorrect speedometer readings, or even tires touching the wheel arches. How do you find out which tires are needed if, for example, you bought a used car and are faced with replacing them for the first time?

There are several ways to do this. The easiest way is to look in the machine’s operating book; you will probably find the necessary data in it. Sometimes we don’t have this opportunity, in which case we can look under the glove compartment lid, where there is a special table with the necessary information. True, there are cars where such a table is not provided. What to do?

Don’t be upset, you can always go to specialized websites that sell tires and fill out the plate (year, brand and other information about vehicle), you will receive detailed information regarding tires that are ideal for your car. If you decide to put tires of a different size on your car, then follow the change linear dimensions Tire calculator will help you with tire tires and speedometer readings.

How to match tires and wheels?

But there are cases, again, they are more often associated with used cars, when it is necessary to select tires according to the size of the rims, because these two components must correspond to each other as much as possible. Then simple rules will help. For example, The width of the rubber profile should be 25–30% larger than the size of the rim. So, for example, if the width of the disk is 5.5 inches, then adding 30% to this value, we get 7.15 inches or 185 mm. It is important that these two details coincide in their central holes. But if for some reason this does not work out, then a special installation ring will come to the rescue. Its outer diameter corresponds to the disk hole, and its inner diameter corresponds to the hub.

But this is not all the features of selecting tires according to. It is also necessary that the tires strictly correspond to the diameter of the circle of the centers of the disc mounts. A maximum deviation of 2 mm is allowed. In this case, special bolts with eccentrics are used for fixation. But it’s best if these parameters match 100%.

To make sure you make the right choice, you can refer to special tables for selecting tires for wheels, which indicate their sizes and compliance.

There is also such a thing as maximum load. Usually, they rarely pay attention to it, since disc manufacturers make their products with a good margin of safety. However, if you decide to experiment and, for example, install rims from a sedan on a jeep, then be sure to find out this characteristic. It is quite possible that the disk will not withstand such a load, and the first hole or bump will lead to very sad consequences.

1. What needs to be done?

You need to choose the right tire for a wheel with the specified parameters or for a specific car.

2. What tire parameters should be taken into account when purchasing?

When choosing tires, you need to consider the following parameters:

• seasonality;
• tread type;
• type of tire design - tubed or tubeless;
• type of cord construction;
• mounting (or landing) diameter;
• tire width;
• profile height;
• load index;
• speed index.

As in the case of choosing wheels, let’s make a reservation right away: if at this stage you no longer want to understand numbers and indices, you can simply use the tire calculator of any large online store or online service, where you can instantly select tires by indicating the model of your car or characteristics of existing disks.

However, if you continue reading, then it has already become clear to you that in fact the above list of parameters is quickly reduced to two or three points, since most of these are obvious or subjective characteristics. Let's go in order.

3. Seasonality

Seasonality is an obvious parameter: at the time of choosing tires, you understand perfectly well whether you need winter or summer tires. The issue of choosing so-called “all-season” tires and its applicability in year-round use is a topic for separate conversation, as well as the choice of mud or “universal”. Here it is only worth saying that they must be marked with the “snowflakes” icon or the letters “M+S” or “M.S”.

4. Tread type

In general, the tread pattern can be symmetrical or asymmetrical, as well as directional or non-directional. Symmetrical non-directional tread is the simplest basic type of tread: these tires are the most common and inexpensive. The directionality of the tread primarily increases its ability to effectively drain water from the contact patch - this. Well, the asymmetrical tread pattern is designed to combine good drainage and directional stability. The issue of choosing a projector pattern also deserves a separate discussion.

5. Type of tire construction - tubed or tubeless

By design, tires are designed for use with or without a tube. However, in modern conditions the question of choosing a tire design is almost predetermined: almost all modern passenger tires– tubeless. Such tires are marked with the inscription “Tubeless” (which means “tubeless”) or “TL”.

6. Type of cord construction

The type of cord construction - the strength part of the tire, its “skeleton” - is also a characteristic that does not require much attention when choosing modern tires: almost all of them today are radial. This fact is indicated by the very letter “R” in the tire marking: for example, the mark “185/70 R 14 88H” means that this is a radial tire with a seat diameter of 14 inches, and not a “radius” of 14 inches, as is often mistakenly said and believed .

7. Mounting (or landing) diameter

This is also a simple parameter if you already have wheels for which you are choosing tires: the seat diameter of the tire must match the diameter of the wheel. If you choose wheels along with tires, you need to check in the instruction manual what diameter wheels are acceptable for use on your model, and only then select tires of the same size for them.

8. Tire width

Tire width is the first digital index reflected in the tire marking. It is indicated in millimeters: the 185/70 R 14 tire has a width of 185 millimeters. This is perhaps the first parameter on our list, which can vary when choosing a tire for a particular wheel or car.

The point here is that the rim can also have different widths, and the tire must fit correctly on the rim. A tire that is too narrow will sit “like a house” on the rim, which is unacceptable due to high risk spontaneous dismantling, and too wide – “mushroom”, which is also unacceptable. Some tuning trends like stance consider the “house” landing to be beautiful and put it in a separate one, but from the point of view of civilian use it is not justified and incorrect.

Each car model has several options for wheel diameter and tire size suitable for use. All these options, recommended by the manufacturer, are listed in the car's operating manual: it is from this data that you should choose. In turn, a rim of a certain width has several acceptable tire options. Here the choice should be made depending on the desired characteristics.

Firstly, wider tires usually provide a larger contact patch with the road and, accordingly, better grip. Secondly, given the same diameter, tires with a larger width have a smaller profile - we’ll talk about it a little lower. Thirdly, wider tires have more weight, which will slightly affect the car's dynamics and fuel consumption. Well, fourthly, as the width of the tires increases, their tendency to . In addition, tires of different widths have different final costs - as a rule, you will have to pay a few extra hundred rubles for additional millimeters. Thus, the width of the tires must be selected taking into account the range allowed by the manufacturer and the desired characteristics.

9. Profile height

The profile height, or series, is the second index reflected in the tire marking. It is indicated as a percentage of the tire width: that is, it is the ratio of the profile height to the width as a percentage. For example, a 185/70 R 14 88H tire has a profile height of 70% of its width. It’s easy to calculate the height in millimeters: you need to multiply the width by the profile and divide by 100 - for our tires this figure is 129.5 millimeters.

The profile height affects the characteristics of the tire. First, the higher profile provides better comfort and puncture resistance. Lower profile tires, therefore, better transfer the road profile to the suspension and body, and are also more prone to damage when hit by defects in the road surface. Secondly, a lower profile provides better handling, and a higher one, on the contrary, provides greater “rollability” of the car. Thirdly, as mentioned above, given the same diameter, tires with a larger width have a smaller profile - this must be taken into account when choosing in accordance with the desired characteristics.

Load index is a parameter that reflects the maximum permissible load on a tire during its operation. It is indicated by a digital index, indicated after the geometric parameters of the tire: for example, our conventional tire 185/70 R 14 88H has a load index of 88. The decoding of the index can be found in the table provided by the tire manufacturer - in our case, the index 88 means a permissible load of 560 kilograms. When choosing tires, it is worth considering that the maximum permissible weight of the car, accordingly, should not exceed the maximum load multiplied by 4 - the number of tires on the car.

Speed ​​index is a parameter that reflects the maximum permissible speed at which the tire maintains its performance characteristics. This is a letter index, the decoding of which also needs to be clarified in the table provided by the manufacturer. Tires of the same diameter can have different speed indexes depending on other parameters - width, profile, composition rubber compound and, accordingly, prices. If the parameter is maximum permissible speed operation is important to you, then you need to choose tires with high price category with the best consumer qualities.

When replacing wheels and tires, taking into account geometric data obtained from tire calculator, it wouldn’t hurt to take a few measurements yourself. Firstly, the distance from the suspension to the wheel surface on the inside, as well as from the shock absorber cup to the tread surface. Secondly, from the wing, as well as steering rods to the tread surface. In this case, the geometric parameters of the new wheel assembly should not greatly exceed the size standard tires and disks. Otherwise, the vehicle may behave unstable.

A few basic rules to remember when replacing tires and wheels.

1. Tread summer tires standardly has a depth of 0.8-1 cm;
2. When installing disks with a larger diameter than standard ones, it is necessary to reduce the amount of offset - for every inch of height, 3 mm of offset;
3. Often the hub holes on discs that are not original have a larger diameter. Therefore, when installing them, you need to use special rings for fixation;
4. In the case when the hole on the disk is smaller than the hub mounts, it is strictly forbidden to drill them out, as well as grind the hub itself;
5. Correct selection of non-original wheels using a calculator will allow you to maintain the driving characteristics of the car;
6. If you are not sure about the compatibility of tires or wheels with your car, it is better not to install, or seek help from specialists.