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How to calculate tire profile height?

The height of the tire profile in its pure form is not indicated on the tire itself. For example, consider a Next read truck tire (remanufactured by Goodyear) marked 315/80R22.5. From the size you can see that the fit diameter (rim size) is 22.5 inches, and the width of the tire profile is 315 mm. Next, a certain number 80 appears, which, as we wrote earlier, indicates attitude profile height (SH) to profile width (SD), expressed as a percentage.

Thus, to calculate the profile height (SH) of a given tire, you need to:

SH = SD x (Profile height to width ratio / 100%)

SH = 315 x (80/100) = 252 mm

Thus, to simplify calculations in the field, we pre-divide the profile height to width ratio by 100, and then multiply the profile width.

In conclusion, we note that the smaller the numerical value of the ratio of the profile height to its width, the smaller the profile height at constant profile width. For example, for size 315/70, the profile height will be 220.5 mm, and for size 315/60 it is 189 mm. In any case, the profile height cannot exceed its width.

Tires of American and European production differ in marking. Often a situation arises when it is necessary to convert inches to centimeters. In this article, we will describe how to decipher tire sizes in centimeters.

Metric tire marking

The main dimensions of tires are prescribed by marking, these include:

1. Tire profile width - the distance, expressed in millimeters or inches, between the outer sides of the sidewalls of an inflated tire, excluding elevations, trim or belts. The specified value should not exceed the product rim width by more than 30%.
2. Tire series. Specifies 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 construction. 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 variant, the cord threads are overlapped. Radial tire design is more common, such tires provide better grip on the road surface, they are more reliable in operation.
2. wheel radius.

How to understand what tire markings mean? The designations on the side of automobile rubber are applied by tire manufacturers. Factory marking is in metric or inch system. For example, the size of tires marked with the metric system 265/75 R15 corresponds to the designation of the inch system 31 × 10.5 R15. The interpretation of these designations in centimeters means:

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

• 265 - a figure that determines the width of the tire (one centimeter is equal to ten millimeters, 265 mm = 26.5 cm);
• 75 is the percentage (75%) that determines the relationship between the height of the tire profile and the width of the rubber (265 * 0.75 \u003d 198.8 mm or 19.9 cm), the found number indicates the height of the tire profile;
• R - denotes the radial type of tires;
• 15 - wheel diameter, the size is indicated in inches, you can convert the specified parameter into centimeters by multiplying the digital value of interest by 2.54, since 1 inch is 2.54 cm, as a result 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 \u003d 26.7 cm);
• R - indicates the radial type of tires;
• 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 \u003d 40.6 cm);
• divide the resulting value by 2 (40.6 / 2 \u003d 20.3 cm).

Differences in the marking of tires

Tire marking with inch system

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

Letter values ​​can be at the end of the tire marking, in which case they mean:

1. "LT" - the tire refers to products with early marking:

• "Numeric" - numerical, tires are designed for vehicles transporting heavy loads, trailers
• "Wide Base" - tires with a wide base, manufacturers make 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" is a commercial tire used for vans and distribution 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 of European manufacturers. The indicated dimension corresponds to the decoding according to the P-metric system, but differs in smaller loads.

• 235 - product width (235 mm = 23.5 cm);
• 710 - a figure indicating the outer diameter of the tire (710 mm \u003d 71.0 cm);
• 460 - tire rim diameter (460 mm = 46 cm);
• A - the designation of asymmetric rubber sides, for example, 460A means that the outer side has a diameter of 45 cm, and the inner one is 47 cm.

Such non-standard markings are designed for vehicles with wheels of a specific size that differ in side profiles from standard metric or inch products. Faced with non-standard markings, it is better to find out their decoding from the tire manufacturer.

Comparison of calculated data

Dimensions requested by the tire calculator to perform calculations

Independent decoding of tire sizes requires a certain accuracy of calculations. You can check whether the conversion of values ​​\u200b\u200bfrom centimeters to inches and vice versa is done correctly 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 systems of sizes at the same time. Therefore, by entering the tire sizes recommended by the car manufacturer in the metric system, it is possible to get a list of American and European tires. It is very convenient, if necessary, to select the brand of rubber of interest, as well as view the possibility of changing tire sizes recommended by the manufacturer. When using tire calculators, it is necessary to take into account the error resulting from rounding, so it is better to translate the dimensions of interest manually, then compare them with the options calculated by the Internet resource.

Conclusion

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

Using the tire calculator, you can easily calculate how the outer dimensions of the wheel, ride height (clearance), speedometer readings and other characteristics will change when you install tires with a different size on your car. The calculator calculates all tire sizes in millimeters, and the vehicle speed in km / h.
Also, the calculator will help you calculate the required rim width for a specific 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 marking in the section: tire marking.

We recommend that you install only the factory tire sizes that are listed in the owner's manual for your machine. Installation of non-standard sizes may void your dealer's warranty and may affect 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 catalogue:

175/70R13-

175/70R13-

When recalculating tire sizes on a calculator, it should be borne in mind that:

With an increase in the diameter of the rim (and, as a result, a decrease in the height of the tire profile so that the outer diameter of the wheel remains unchanged), the load on the car suspension increases, as well as comfort worsens (the car will become noticeably stiffer).

With an excessive increase in the tire profile, the car becomes a “roll”, it is worse controlled, and at critical values ​​\u200b\u200bof the profile height, the tire may begin to cling to body parts and suspension of the car, which will subsequently lead to its destruction.

What is a tire calculator for?

With this tire calculator, you can easily calculate how the outer dimensions of the wheel, ride height (clearance), speedometer readings and other characteristics will change when you install tires with a different size on your car.

Old tire size

Width

Height

Diameter

New tire size

Width
Select 5.0 5.5 6.0 6.5 7.0 7.5.5 8.5 9.5 10.5 11.5 12.0 12.5 13.0 13.5 14.5 125 135 145 155 175 175 295 195 205 215 225 235 295 355 335 335 335 355 365

Height
Select 25 27 30 31 32 33 34 35 38 38.5 40 45 50 55 60 65 70 75 80 85 90

Diameter
Select 12 13 14 15 16 16.5 17 17.5 18 19 20 21 22 23 24 25 26 28 30 32

First enter the standard size installed on your car, and then the one you want to install.

The difference between the speedometer and the actual speed depends on the speed of the car, the higher the speed, the greater the difference

	External dimensions	old	New	Difference
	Tire width, mm (A)	0	0	0
	Profile height, mm (B)	0	0	0
	Disc diameter, mm (C)	0	0	0
	External diameter, mm (D)	0	0	0
	Change in ground clearance, mm			0

The site of the online store contains a convenient tire calculator that makes it easy to calculate changes in wheel parameters when switching to another tire size. With this online tool, you can calculate external wheel measurements, ground clearance (ride height), calculate speedometer readings and other characteristics.

With the onset of the new season, every responsible car owner considers it necessary to change tires in accordance with the season. The best option would be to install tires of the size recommended by the automaker for a particular car brand. In cases where this is not possible, deviations in diameter in the 2% range are allowed.

Replacing tires requires a serious approach. When choosing new tires and wheels, it is necessary to take into account such indicators as:

• tire width,
• profile height,
• wheel inner diameter,
• valid speed indices.

Incorrectly selected tires can cause malfunctions in the car's electronics, increase fuel consumption, worsen driving comfort, and also cause problems during a vehicle inspection at the traffic police.

How to calculate tires?

To select the tires of the required size, you need to use the tire calculator, which determines the theoretical dimensions. All measurements are in millimeters and speed is in km/h. To make a calculation, you should enter the parameters of the tires of your car in the appropriate line. Then enter the dimensions of the new tire and rim to be installed. After specifying all the parameters in the table below, information will appear on changes in the tire width and profile height, inner and outer diameter, the difference in speeds (real and according to the speedometer).

What to look for when choosing a tire

• Installing tires and wheels of non-standard size can lead to damage to the tire itself, damage to the wheel and reduce the performance of the car. When choosing tires, it is better to rely on the recommendations of the automaker.
• If the diameter of the wheel disc is larger, then in this case the load on the suspension may increase. To maintain the same diameter of the outer wheel, the height of the profile should be reduced.
• If you choose tires with a greatly increased profile, you need to be prepared for a loss in the quality of car handling. The tire can rub against the body and suspension, causing rapid wear.
• Even with the slightest difference between the indicators on the speedometer and in reality, the error can increase many times with an increase in speed, which makes driving unsafe.
• Narrow or too wide rims can cause tire deformation. This, in turn, will lead to premature wear and deterioration of performance.

When factory tires wear out or you want to install new rubber, the following question arises: which type of tire will fit perfectly? Each make and model of car is designed for an individual tread and wheel parameters. All the necessary information is contained in the technical documentation or on the vehicle body - on the gas tank cap from the inside.

The online store of tires and wheels "MOSSHINA" has developed a special tire calculator online, with which it is possible to determine the differences between tires in percentages, inches and centimeters.

Visual tire calculator

It is extremely important to choose the right size tires. If you make a mistake and deviate from the factory standard sizes even by a few percent, then the sensors will begin to distort the current information, fuel consumption will increase, and driving itself will become unsafe.

Tire calculator: tire comparison

Using our electronic form, you can quickly and easily compare wheel circumference and diameter, profile, tread. In addition, the tire calculator displays differences in suspension clearance, vehicle speed and engine speed.

Tire calculator visual online: terms of use

In the upper left corner there are two forms to fill out:

• Previous size (standard size of the original tire);
• New size.

In the fields from left to right, you need to enter the tire width (millimeters), the height-to-width ratio (percentage) and the rim diameter (inches). These indicators are indicated on the tire profile. For convenience and clarity, an image of a tire and a disk is displayed, which can be turned on and off.

When all fields are filled in, the tire calculator will calculate the difference and provide all the information in the table on the right. If the difference is 3% or more, then we do not recommend installing such tires.