How to determine the size of a car's rim

Wheel size

Reading time: 8 minutes

Car owners around the world are often faced with the problem of replacing their wheel rims. This happens due to forced reasons - when they are deformed, broken, worn out, or at the request of the car owner himself, due to a too unpresentable appearance, small size and for other reasons. Thus, the car accessories market is always ready to offer its customers a wide range of products and goods for every taste and budget.

What is the standard disk size?

The standard wheel size is a characteristic of the wheels that are installed by the automobile concern at the factory in accordance with the requirements of technology, the class of the vehicle, as well as strength calculations carried out by the engineering personnel of the enterprise.

Wheel store

Coming off the assembly line, the car acquires the following basic wheel rim parameters:

The shape of the rim flange, designed to securely fix the tire. This parameter for passenger cars, regardless of model and modification, is usually expressed in the letter designation J or JJ.
The width of the rim of the product, on which the final tire size depends. It is expressed in inches in increments of 0.5 units. As a rule, standard car brands have a range of this dimension from 4 to 12 inches, which corresponds to tires from 145 to 345 mm.
The most important parameter is the radius of the product, which is defined as the diameter of the rim without taking into account the edges and ranges from 12 to 24 inches, respectively, written as R12, R13, ..., R22, R23, R24. The radius of the tire, which should be similar to this value, as well as its profile, depending on the size of the wheel arch and the technical requirements of the manufacturer, depend on this important parameter. So, on the R16 for the Toyota Land Cruiser 200 you can install tires with a profile height of 90 mm. The same radius, but for the VAZ 2110, entails only low-profile tires with a dimension of 35-40 mm.
Also at the factory, the wheel offset range required for a specific brand is assigned, that is, the ET parameter, or the value in projection from the place where the disk is fixed to the hub to its mating plane on the inside. So, the larger the ET value, the deeper the wheel will sit under the wheel arch and vice versa. This disc dimension can be negative, and in this case the disc will protrude slightly beyond the dimensions of the body. The average range of this parameter is from -25 mm to +50 mm.
If the previous parameters allow for a slight variation in wheel dimensions, then such indicators as drilling and bolt pattern, as a rule, must be the same, otherwise the wheel simply will not fit on the hub.

Disc rim width and seat dimensions

Wheel drilling is the size of the central hole of the disk, with which it fits onto the axle. As a rule, it ranges from 50 to 120 mm, depending on the model, brand and class of the vehicle.
The disc bolt pattern is a parameter that determines the number of studs on the hub and their length. Designed for mounting wheels. For small cars, the studs are made with parameters 4×98, 4×100, that is, the disc is fixed to 4 anchors, each 98 or 100 mm long. In the case of business, premium class cars or SUVs, the number of fasteners increases to 5 or 10 pieces, and their length can increase to 150 mm.

How to determine the size of alloy wheels and stampings for a car

Of course, each original disk on a car is marked, and upon detailed inspection you can see a line with all the geometric parameters listed above. If for some reason, for example, in case of wear, this value is not readable, then you can always measure the wheel and display its marking yourself. This is done as follows:

To determine the width of a product, you simply need to measure its rim in millimeters with a ruler or tape measure, and then divide the result by 25.4 mm to convert it to inches.
The radius of the product is determined in a similar way, only here the diameter is measured. Many people mistakenly believe that the value with the R symbol indicates the radius of the disks, but this is fundamentally incorrect and it is the greatest distance between two points on the wheel rim that needs to be measured. In this case, for the accuracy of measurements, it is necessary to ensure that the measuring tool passes strictly through the center of the disk, because otherwise the car enthusiast will only be able to measure the chord, and the disk radius indicator will be incorrect. The result obtained must be divided by the same 25.4 cm to obtain the parameter value in inches. It should be noted that the measurement may well have an error of +/-5 mm, since radius can only be expressed as a whole number.
The most difficult thing is to measure the wheel offset, that is, determine the ET parameter. To do this, you need to lay the wheel flat, install a wooden strip on it, equal in length to the diameter of the metal part, and then measure the distance in millimeters to the mating plane of the disk. Then the wheel is turned over 180 degrees, and the procedure is repeated again, but for the reverse side of the product. The results obtained must be substituted into the formula ET = (X + Y)/2, where X is the first measurement, Y is the second, and ET is the desired offset indicator, all units here are indicated in millimeters.

Other disk size characteristics

To determine the drilling or diameter of the mounting hole, the car enthusiast only needs to measure the greatest distance between the edges of this perforation, and then look at the nearest typical value in the table of correspondences and deviations. The size of the wheel rim holes depends solely on the design of the hub for a particular car brand.

The size of stamped discs is determined according to the same scheme, without any special features.

Decoding the wheel size

So, in order to correctly decipher these inscriptions, below are some specific examples that a car enthusiast can see on his rims.

The owner of a Lada who has decided to change the wheels to more presentable ones, as a rule, sees on the disk the inscription 5.5J x 15 ET42 d56.1 4x98, which means a wheel disk with a rim width of 5.5 inches, a J edge shape, non-separable ( indicator “x”), with a radius of 15 inches, a positive wheel offset of 42 mm, a mounting hole diameter (drill) of 56.1 mm, mounted on 4 studs of 98 mm each (bolt pattern indicator).
The letter J, depending on the class, weight and model of the vehicle, can be replaced by JJ, K, JK, B, P or D, which must correspond to the marking of the purchased disk.

Determining wheel offset

Also on the wheel there may be a hump or H designation, for example, 6.0J x 17 H2 ET38 d65.1 5x112. Hump refers to special protrusions along the sides of the disc, which increase the reliability of fastening the rubber to the metal. So, this indicator can be marked as H - single hump, on one side of the wheel, H2 - double, respectively, on both edges, or X (truncated hump).
In addition, for drivers of minivans, pickup trucks and other vehicles designed to transport loads over 900 kg, it is very important to purchase highly durable products that can withstand significant loads.

In addition, an important indicator of the strength of the product is the maximum tire pressure characteristic, and on the rim, as a rule, they write a value such as Max PSI 50 Cold, that is, the maximum tire pressure cannot exceed 50 pounds per square inch, or after translation - 3.5 kilograms per square centimeter.

The prefix Cold means that such measurements should be carried out exclusively on a cooled wheel, because, as is known, when heated, for example, in hot weather, the gas inside the wheel expands and has a stronger effect on the rubber from the inside. Accordingly, together with the softening of the polymer material due to high temperature, when operating overinflated wheels, there is a high risk of their rupture, which can lead to an accident on the road.

The last thing that can be read on the rim is letters such as SAE, TUV, ISO or ROSTEST, and all these characteristics mean an indicator of the quality of the product, that is, that it has passed mandatory certification after a series of tests on special stands and in full complies with the Russian and international standards required for it.

Other methods for determining disk sizes

Often the buyer does not want to deviate from the sizes of car rims dictated by the manufacturer of the car brand he owns, and then it will be enough to select a wheel rim according to the characteristics specified by the manufacturer. Thus, in many large points of sale, consultants have a specialized program installed on their computers that makes it easy to select the right wheels.

The client turns to the hall employee for help, and the specialist enters the make, model, modification of the vehicle, its year of manufacture, as well as other parameters if the system requests them, into special fields in the program.

As a rule, such systems are interfaced with a warehouse accounting program, and the seller immediately has the opportunity to inform a potential buyer about the availability of products at the point of sale, about the brands that produce these products, as well as about their prices, and the client can immediately decide on the design of the grille, material, disk size, and also correctly calculate your budget for the purchase.

Thus, the client will always be confident in the quality of the product, as well as in the selection of the absolutely correct size, and the warranty will never be removed from his car. Of course, many car enthusiasts are not satisfied with the too harsh pricing policy of official dealers, but the guarantee of long, reliable and safe operation more than pays for all overpayments by the client, and if you find out the prices from brand representatives, they are not much different from other outlets selling quality products.

It should also be taken into account that an incorrectly selected wheel size often leads to rapid wear of the calipers, brake system, hubs and other suspension elements, which will result in much larger repair costs.

Disc markings, symbols, terms on discs, designations

To choose wheels for your car, it is not enough to know the required diameter and the number of bolts for fastening. The disk must meet a number of parameters. The full disk size looks like this: 6.5×16 5/100 ET48 d56.1 . The ability to decipher symbols on disks will help you avoid mistakes when purchasing and disappointments when installing them on a car.

6.5 - rim width value . Indicated in inches. If you want to know the size in millimeters, then 6.5 must be multiplied by 2.54 (1 inch).

j (can be replaced by “ H2 ”) - for ordinary consumers these values are not important, because are service designations for manufacturers and sellers.

J is a value that encodes data on the design features of the edges of the rim flanges, such as their angles of inclination, radius/radii of curvature, etc.

H2 (short for Hump) - the presence of this designation indicates that there are annular projections (humps) on the rim flanges that keep the tubeless tire from sliding off the rim. The letter designation H means single (simple) hump. H2 - stands for double hump. There is also a Flat Hump - FH , Combi Hump - CH , Asymmetric Hump - AH . If there is an x sign between the designations of the width of the disk and its mounting diameter (as in this case), this means that the disk rim is one-piece, without humps.

5/100 - indicates the PCD value of the wheel (Pitch Circle Diameter). The number “5” is the number of fastening holes for nuts (bolts) on the disk, and in millimeters “100” is the diameter along which the fastening holes are located. If necessary, and there are no special instruments at hand, measurements can be taken with a regular stationery ruler.

IMPORTANT: The wheel mounting holes can be located on different diameters, which have a very tight tolerance relative to the central hole.

Warning! The mounting holes may have a small plus tolerance in diameter, which visually makes it difficult to accurately determine the PCD if it differs from the standard one by only 2 millimeters. For example, a wheel with a PCD value of 4/98 is often installed on a hub with a PCD value of 4/100. IS IT DANGEROUS. Only one nut (bolt) will be fully tightened. The mounting holes of the remaining 3 nuts will “lead”, as a result they will be undertightened or tightened skewed. As a result, the wheel will not be completely seated on the hub. When driving it will “beat”, there is a high risk that the nuts will gradually unscrew by themselves.

d - (example: d 66.6) - in millimeters indicates the diameter of the hub , or the value of the diameter of the central hole of the wheel. It is important that this parameter exactly matches the diameter of the vehicle hub mounting cylinder. Matching the sizes will ensure preliminary centering on the wheel hub, which will facilitate installation of the bolts.

ET - letter designation of disc offset , i.e. distance in millimeters from the mating plane of the wheel rim mounted on the car hub, and a conditional plane that runs in the middle of the wheel rim.

ET “positive” - the mating plane does not protrude beyond the conventional boundary.

ET “negative” - the mating plane is behind the imaginary plane.

In some countries, there is another designation for ET - OFFSET or DEPORT.

Examples of departure designations:

ET 46 - positive offset, 46 millimeters.

ET-20 - negative offset, 20 millimeters.

ET 0—zero offset.

Warning! It is dangerous to install wheels on a car whose disc offset differs from the standard one recommended by the car manufacturer. In an effort to give the car a sporty look, some car owners install wheels with a reduced offset. The car becomes a little more stable on the track, because... the wheel track becomes wider. And at the same time, the load on the car’s suspension and wheel bearings increases. And vice versa, it is impossible to increase the wheel offset - its wheel rim will rest against the brake disc. All this can lead not only to car breakdown, but also to an emergency on the road.

The wheel may also have the following symbols:

— Date of manufacture — (example: 0309) — means that the release date of the disc is the third week of 2009.

- ISO, SAE, TUV - the mark that is given by the regulatory body. This marking is confirmation that the wheel complies with international standards/rules.

— MAX LOAD 2000LB is the most commonly used value for the maximum wheel load capacity (in pounds or kilograms). In this example, the maximum permissible load limit is 2000 pounds, i.e. 908 kilograms. — PCD 4/100 — parameters of connecting dimensions; — MAX PSI50 COLD — maximum air pressure in the tire. In this example, no more than 50 pounds per square inch (3.5 kgf/sq.cm). “COLD” - translated as “cold” - a reminder that pressure measurements must be taken in a cold tire.

Recommendation from specialists at the online wheel store Kolesa Darom

Even if you feel that the technical terms are more or less clear to you, it is still better to select disks by consulting with a specialist directly at the time of purchase. This, at a minimum, saves money and time. And, as a maximum, it will save you from mistakes and, as a result, dangerous situations on the road.

Wheel rim bolt pattern compatibility table

Replacing your stock wheels with ones of a different shape or size can certainly give your car an exclusive look. This type of tuning is very popular and is practiced by most car owners. But simply changing the wheels for more beautiful ones won’t work. Here it is important to take into account some technical parameters provided by the car manufacturer and wheel manufacturers.

We recommend that you read the article about which wheels are best for cars.

How discs are marked

Each disc has an individual marking indicating:

•number of holes for mounting to the hub;

•diameter of a conventional circle passing through the axes of these holes;

Wheel rim bolt pattern compatibility table

Let's look at an example of full marking 9JX16 Н2 5/112 ET 35 D 66.6

9 – disk width (in inches);

J – designation indicating that the disk is intended for a one-wheel drive car (wheels for all-wheel drive vehicles are designated by two letters JJ);

X – disc manufacturing method (cast);

16 – installation diameter (in inches);

H2 – marking indicating the number of annular protrusions holding the tubeless tire (2);

5/112 – number of mounting holes/diameter of the circle on which they are located (bolt pattern);

ET 35 – disc offset value (in millimeters);

D 66.6 – diameter of the central (hub) hole of the disk.

How to determine bolt pattern

Each make and model of car has individual bolt pattern parameters. There are special tables for this, based on which you can select disks.

If it is not possible to use tables, or if your car is not included in them, you can determine the bolt pattern yourself. To do this, we count the number of holes for mounting the disk. The first parameter is there. Determining the diameter of the circle on which the holes are located is a little more difficult.

For disks with 3 holes, measure the distance between the walls of adjacent holes and multiply it by 1.155. The result obtained will be the desired diameter.

For disks with four-point mounting, measure the gap between the walls of opposite holes and multiply it by 1.414.

For five-bolt wheels, measure the distance between the two farthest holes through one, and multiply by 1.701.

Disc overhang size

Offset is one of the most important criteria for selecting wheels. It determines the distance between the vertical axis of symmetry of the disk and the plane of contact between the disk and the hub.

Disk offset occurs:

•positive (the vertical axis of the disk is located behind the mating plane);

•zero (the disk axis is superimposed on the mating plane);

•negative (the disk axis is located in front of the mating plane).

The disc offset parameters are strictly regulated by the vehicle manufacturer and are directly related to the suspension kinematics. A change in the standard overhang value is allowed by no more than 5 mm.

Below are tables indicating the bolt pattern, offset and diameter of the central hole of the disks for popular car models.

Wheel rim bolt pattern compatibility table

Tire and wheel sizes part 1. Marking and selection of car rims.

Marking and selection of car rims. A striking example of how easily different measurement systems can coexist and how deeply this confusion has entered our lives.

Number and bore diameter of the location of the wheel rim mounting holes. - fastening to the car
Disc central hole, hub diameter. — fastening to the car
Wheel rim width. — fastening to the tire (tire)
Wheel rim diameter. — fastening to the tire (tire)
Wheel offset. Wheel removal. - wheelbase width
Disc rim flanges, side flanges. — fastening to the tire (tire)
Rim shelves and bumpers. - fastening to the tire (tire)
Other possible designations.
Wheel mount. The procedure for tightening bolts (nuts).
Recommended tightening torque depending on the wheel thread diameter

You can familiarize yourself with the decoding of tire designations here.

The number and mounting diameter of the location of the wheel rim mounting holes.

6.5J×15 H2 5/112 ET39 d57.1 - “five holes with a diameter of 112 mm”

The second number is the diameter in mm at which the centers of these holes are located, which is called PCD = Pitch Circle Diameter and in our case it is 112 mm. In the tire industry, for chic, both of these parameters are often called “PCD”, and when indicating the PCD of a disk they write 5/112. The wheel mounting holes are located at different diameters with tight positional tolerance in relation to the central hole. There is a limited number of such diameters (examples are 98, 100, 112, 114.3, 120, 130, 139.7 and some others; they are used by automakers either by tradition or as the most suitable for certain types of cars - for example, size 139, 7 is typical for pickups and SUVs). Occasionally there are wheels with two “sets” of 4 or 5 mounting holes, located on two different diameters.

Disc central hole, hub diameter.

6.5J×15 H2 5/112 ET39 d57.1 - “hole for hub 57.1 mm”

d 57.1 - Diameter of the centering hole on the disk. Must exactly match the diameter of the landing cylinder on the hub. Often the same wheel (wheel rim) is offered for cars from different companies, so the central hole in the wheel rim must be different. Because in addition to the centering function, the landing cylinder has another, no less important one - it partially takes on the load that falls on the mounting bolts (studs). Therefore, if the centering hole of the disk you like is larger than the hub mounting cylinder, you will have to use special centering rings, which can be bought at tire centers, or ordered somewhere. The external and internal dimensions of the centering ring must correspond exactly to the diameters of the hub cylinder and the centering hole of the disk, respectively.

Wheel rim width.

A disc wheel consists of two main parts: the rim and the disc itself. The disc is the central part of the wheel, with which the wheel is attached to the car hub with bolts or nuts. The rim is a cylindrical part of a wheel with a special profile, which is located perpendicular to the disk and serves to mount a rubber tire on it.

6.5 J×15 H2 5/112 ET39 d57.1 - “disc (rim) seat width 6.5 inches”

DIMENSIONS: always given in inches (1 inch = 25.4 mm), except for Michelin designs, which give dimensions in millimeters.

ATTENTION: The width and diameter are selected according to the size of the rubber tire. To determine the overall width of the wheel rim, add another 26 mm to the rim width value on the marking. that is, the thickness of the outer and inner side edges. The overall width of the rim should be 12 (plus or minus 4) mm less than the width of the rubber tire profile

Wheel rim diameter.

6.5J× 15 H2 5/112 ET39 d57.1 - “wheel diameter (size) 15 inches”

15 – landing (!not overall!) diameter of the wheel rim in inches, which must correspond to the landing diameter of the tire. Passenger cars use wheels with a diameter of 12 to 32 inches, the most common diameters being 14-16 inches. 1 inch=25.4 mm.

Wheel offset . Wheel removal.

Disk offset is the distance between the mounting plane of the wheel (the plane of which the disk is pressed against the hub) and the middle of the disk width (an imaginary plane passing through the middle of the rim).

To determine the wheel offset, you need to measure dimension “B” on the inside of the wheel. Divide size “X” in half. Subtract size X/2 from size “B”. If the difference is positive, then the offset is positive; if it is negative, then the offset is “negative”. Or, in other words:

The offset is “positive” if the mating plane does not go beyond the imaginary plane.

The offset is “negative” if the mating plane passes through an imaginary plane.

Disc rim flanges, side flanges.

6.5 J ×15 H2 5/112 ET39 d57.1 - “type J rim flange”

J (JJ, JK, K,B, P, D...) This letter encrypts technical information about the edges of the disc rim (design, shape, height). The most common types of disks today are J (mainly for single-wheel drive vehicles), and JJ (usually for all-wheel drive). The flanges of the rim of the rim affect the installation of rubber, compensating weights, as well as the resistance to displacement of the tire on the rim in extreme conditions. Obviously, despite the external interchangeability of, for example, J and JJ disks, it is still better to choose the parameter recommended by the car manufacturer.

Wheel rim and champa shelves.

6.5J×15 H2 5/112 ET39 d57.1 - “shelves rims and humps type H2”

H (H2, FH, AH, CH...) – these letters encrypt information about the design features of the disk rim flanges and the protrusions (hamps) on them. Humps are designed for tubeless tires and ensure correct installation of the tire on the rim. Some tires require special wheel parameters in this regard; this point needs to be clarified when purchasing tires. In general, a car enthusiast does not need to delve deeply into the essence of these designations.

Other possible designations.

The disk may also indicate:

Date of manufacture . Usually a year and a week. For example: 0504 means the disc was released in week 5 of 2004.
SAE, ISO, TUV, PCT. - stamp of the regulatory authority. The marking indicates that the wheels comply with international rules or standards.
MAX LOAD 2000lb - a very common designation for the maximum load on a wheel (denoted in units of mass - kilograms or pounds). The maximum load listed here is 2000 lbs (908 kg).
MAX PSI 50 COLD - means that the tire pressure should not exceed 50 psi (3.5 kgf / sq. cm), the word COLD (cold) means that the pressure should be measured when the tire is cold.
Other

Dimensions and parameters of car wheels

The selection of car wheels should be treated with great care and attention! Each disk has several parameters for installation on a car, each of which must be taken into account when choosing. Some parameters are unchanged, while others can be adjusted within a small range. This article will tell you about all the intricacies of choosing cast and forged wheels.

Disk options

Size A (rim diameter in inches) – seat diameter – the diameter of the annular part of the rim on which the tire rests.

Dimension B (rim width in inches) - rim seat width - the distance between the inner surfaces of the wheel flanges. Determines the possible profile width of the installed tire. A deviation of 0.5-1 inch in the seat width is allowed, but for low-profile tires it should be minimal.

HUMP ( width in inches) – an annular protrusion, used for additional fixation when installing tubeless tire beads.

ET (offset in mm) – offset (offset) of the disk, i.e. a parameter that determines how deep the wheel is recessed into the car arch. The offset is the distance from the plane of the disk adjacent to the car hub to the plane passing through the axial middle of the width of the disk rim. For each vehicle, the manufacturer provides a list of acceptable wheel installation options. This parameter can be changed by +/- 5 mm without harm to the car's suspension. If the deviation is large, it is necessary to try on the disc on both the front and rear axles of the car, since it is possible that the disc will rest against suspension elements, fender liners or parts of the car’s brake system. In addition, installing wheels with an offset that is significantly less than intended leads to a significant decrease in vehicle stability in corners, increased steering sensitivity to road irregularities and uneven braking forces.

PCD – the number of mounting holes and the diameter of the circle of the centers of these holes. This value must correspond to the standard value, otherwise it is impossible to achieve reliable fixation of the wheel on the car hub. A deviation of even 1-2 mm can lead to misalignment of the wheel and fastening elements.

DIA (CO in mm) – diameter of the central hole of the disk. It must match the diameter of the centering protrusion on the vehicle hub. An upward deviation of its value is allowed. In this case, adapter centering rings are used to install the wheel.

Disk parameters can be indicated as follows, for example:

6×15 ET45 5×100 D57.1

6 – rim width in inches;

15 – disc diameter in inches

ET45 – disc offset (in mm);

5×100 – PCD , the number of mounting holes at a certain diameter location. It must be taken into account that for each car it (diameter) is different and cannot be changed under any circumstances;

D57.1 – DIA (TsO) diameter of the central hole of the disk, measured in mm;

6.5 J 15 H2 5×114.3 ET45 D54.1

6.5 – rim width in inches;

15 – disk diameter in inches;

5×114.3 – PCD , number of mounting holes at a certain diameter location.;

ET45 — disc offset (removal) (in mm);

D54.1 – DIA (TsO) diameter of the central hole of the disk, measured in mm;

J and H2 are symbols needed more by specialists. J encrypts information about the design of the rim flanges (can be JJ, JK, K or L) . And H2 is the design code for humps, ring protrusions on the rim flanges that serve to reliably hold the tubeless tire on the rim (there are many variations: H, FH, AH, etc.);