Finding information about wheel rim parameters is one of the most common tasks when selecting new tires or purchasing a set of wheels on the secondary market. It often happens that the original stickers have long been torn off, and the paper tags are lost during the first wash. At this moment, the car owner is faced with a question: where are the markings on alloy wheels in order to accurately find out their sizes and compatibility with the car? The answer lies in the standards of manufacturers, which oblige all technical data to be applied directly to the metal of the product.
Usually basic information knocked out or cast on the inside of the disk, hidden from view when the wheel is installed. To see these numbers, it is not at all necessary to remove the wheel from the car, although this greatly simplifies the process. It is enough to turn the steering wheel all the way and look into the arch, illuminating the inner surface of the spokes with a flashlight. It is there, on the jumpers or the end of the hub part, that the desired engraving is located.
It is important to understand that there is no single global standard for the placement of this data. Some manufacturers prefer to hide the numbers deep at the hub, others place them on the outside of the spokes, and still others use the back of the rim. Knowing the exact location of the markings will save you time and nerves when selecting spare parts, and will also allow you to avoid mistakes when purchasing unsuitable discs.
Typical places where information is written on a disk
The search should begin from the inside of the disc facing the brake caliper. In 90% of cases, it is there, on one of the spokes or on the inside of the rim, that you can find the stamped numbers. Most often the marking is located on back side of the knitting needles, closer to the hub or, conversely, closer to the edge of the rim. If the disk has a complex Y-shape of spokes, look for the data on a wide part of the metal where it is convenient to place a long string of characters.
Sometimes, especially on premium brand discs or models with complex designs, engraving can be found on inner ring of the rim. This is the annular surface that fits against the bead of the tire. To view the lettering in this area, it is often necessary to remove the wheel or use a small mirror, since the viewing angle through the wheel arch may be limited by the suspension components.
⚠️ Attention: Never try to clean dirt or oxides from markings with sharp metal objects or aggressive chemicals. You risk damaging the deep relief of the numbers, making them unreadable, or damaging the varnish coating, which will lead to corrosion.
There are rare exceptions when the manufacturer places the parameters on the outside of the spokes, but this is more typical for designer models, where the dimensions are part of the visual style. Also, on some Japanese wheels, markings may be applied to a welded metal plate or stamped on hub hole. If you do not find the data in standard places, carefully inspect the entire inner surface in a circle.
Structure of the main marking line
Once you have found the engraving, you will be presented with a series of numbers and letters separated by multiplication symbols, fractions, or just spaces. The most important part is the main line, which looks something like this: 8.5J x 18 H2 5/112 ET 35 D 66.6. This code is easy to understand if you know the sequence of parameters. Always goes first rim width in inches, followed by the flange type (most commonly J), and then the diameter.
Next on the line is the number of mounting holes and their location diameter (PCD), followed by disc offset (ET) and center hole diameter (DIA). Understanding this sequence is critically important, since confusing offset with diameter or width with bolt pattern means buying a disk that will not physically fit on the car or will interfere with suspension elements.
Sometimes the line may be split into two parts or supplemented with a designation of the type of casting, for example, CAST or FLOW FORMING. Quality standard designations may also be present, such as VIA (Japan) or TÜV (Germany), which confirm the safety of the product. These characters are usually found at the end of a line or in a separate block next to the main information.
What do the letters after the diameter mean?
The letters H, H2, FH, P after the diameter value (for example, 18 H2) indicate the shape of the rim flange, which affects the fit of the tubeless tire. For most passenger cars, this parameter is standardized, and you don’t need to pay close attention to it when selecting it if you are not involved in professional tuning or racing.>
Explanation of key parameters: width and diameter
The first two digits in the marking indicate rim width in inches. For example, the number 8.5 means the tire seat width is 8.5 inches. The profile width of the installed rubber depends on this parameter. Installing a tire that is too narrow or too wide on a rim can result in an improperly formed contact patch, which will negatively affect handling and safety.
Immediately following the width is a letter indicating the flange profile. The letter is almost always found on passenger cars J. There are also profiles JJ, K, L, but they are typical for SUVs or specialized equipment. After the letter it is indicated disc diameter inches is the distance between the inner edges of the rim, not the total outer diameter of the wheel and rubber.
Diameter is one of the most noticeable parameters, and it’s difficult to make a mistake here, but it is impossible to fit R17 tires onto a 16-inch diameter disc, and vice versa. A discrepancy between the wheel and tire diameters will make the vehicle impossible to operate.
Bolt pattern and center hole diameter
The PCD (Pitch Circle Diameter) parameter in the marking is indicated by two numbers separated by a multiplication sign or an asterisk, for example, 5x112 or 4x98. The first number indicates number of mounting holes, and the second - on the diameter of the circle along which they are located. This is a critical parameter: even a discrepancy of 1-2 mm will make the installation of the disk impossible or will lead to the fact that the nuts will not hold.
The diameter of the central hole, denoted as DIA or D, indicates the size of the hole in the center of the disk where the vehicle's hub fits. In the marking it looks like D 66.6 or DIA 57.1. If the diameter of the hole on the disc is larger than on the hub, installation of centering rings will be required. If it’s less, the disc simply won’t fit on the car.
In some cases, disc manufacturers make universal holes with a margin, completing them with a set of insert rings of different diameters. The marking of such disks may indicate the maximum diameter, and plastic or metal adapters may be included. Always check that these rings are present when purchasing used wheels, as without them the wheel will wobble at speed.
| Parameter | Designation | Example | Impact on the car |
|---|---|---|---|
| Width | Digit (inches) | 7.0 | Contact patch width |
| Bolt pattern | PCD | 5x114.3 | Possibility of fastening |
| Departure | ET / Offset | 45 | Wheel position in the arch |
| CO | DIA / D | 60.1 | Wheel alignment |
Disc offset (ET) and its meaning
One of the most important and often misunderstood parameters is disc offset, denoted by the abbreviation ET (from German Einpresstiefe) or Offset. In the marking it looks like ET 35 or OFFSET 40. The offset is measured in millimeters and shows the distance from the vertical plane of symmetry of the disk to the mating plane where the disk is adjacent to the hub.
The lower the offset number, the more the disc protrudes outward from the arch. And vice versa: a large offset “recesses” the wheel deeper under the body. An error in selecting the offset, even by 5-7 mm, can lead to the wheel starting to rub against the spar, suspension elements, or, conversely, sticking out too much, creating a load on the wheel bearing.
☑️ Checking disk parameters
There is a myth that the crash can be ignored if the disk “seems to fit.” This is a dangerous misconception. The change in the run-in arm, which occurs when the offset changes, changes the load vector on the suspension. This can lead to accelerated wear of the rubber, knocking noises and even destruction of the steering elements.
Additional designations and quality standards
In addition to geometric dimensions, you can find various abbreviations on the discs indicating production technology and certificates. For example, marking JWL indicates compliance with Japanese standards, and TÜV - into German. For light alloy wheels, the designation is often found AL (aluminium) or the chemical composition of the alloy.
There may also be information about the maximum tire pressure (MAX PRESS) and maximum disk load (MAX LOAD). These parameters are important for owners of SUVs and commercial vehicles, where the weight of the vehicle and cargo plays a critical role. Excessive load can lead to deformation or destruction of the disc.
⚠️ Attention: If the disc is stamped "X2" or "TEST", this may mean that the disc is a pre-production sample or has been re-tested. Be careful when purchasing such products, their origin and actual strength may not correspond to the declared characteristics of mass-produced products.
There are also production dates, which are often embossed in the form of a dial or week and year code. Knowing the production date is useful when purchasing used wheels, since the age of the aluminum alloy and the condition of the paintwork directly affect the service life of the product. Old discs may have microcracks that are invisible to the eye.
How to read markings using examples
Let's look at a specific example line: 9Jx19H2 5/120 ET45 D72.6. Here 9 is the width of the rim in inches, J is the flange type, 19 is the diameter. 5/120 means 5 holes on a diameter of 120 mm. ET45 has a 45mm offset and D72.6 has a 72.6mm center bore. Seeing such a line, you immediately understand that the disc will fit, for example, on some BMW or Land Rover models, but will not fit on a Toyota or Ford due to different bolt patterns.
Another example: 7.5x16 4x100 ET38. This is a typical size for a class B or C class compact car. 7.5 inches wide, 16 diameter, 4 holes at 100mm diameter, 38mm offset. Failure to indicate DIA in the short notation often means that the hole diameter is standard for the bolt pattern, but it is best to double-check this with a ruler or caliper.
If you see fractional values in the departure, for example, ET 35.5, that's normal. The precision of manufacturing cast wheels allows such tolerances. The main thing is that the deviation from the car’s factory parameters does not exceed the recommended limits (usually ±5 mm for steel and ±2-3 mm for alloy wheels).
Common mistakes when reading labels
One common mistake is confusion between inches and millimeters. The width and diameter are always specified in inches, and the offset and diameter of the center hole are always specified in millimeters. Trying to interpret the width of 8.5 as millimeters will lead to comical but dangerous conclusions. It is also common to confuse the hole circle diameter (PCD) with the diameter of the bolt hole itself, which are completely different values.
Another mistake is to ignore the letter J or H. Although less critical for normal driving than PCD, installing a B profile wheel instead of a J on a modern low profile tire can cause the tire bead to not stay sealed and cause the tire to go flat.
Some car enthusiasts mistakenly accept the maximum load marking (MAX LOAD 690kg) for the weight of the disc itself or the recommended axle load. This is the limit that the drive can withstand if it fails and is not a guide for daily overload use.
Is it possible to install a disc with a large central hole?
Yes, you can, but you must use centering (spacer) rings. They eliminate the gap between the hub and the disc, ensuring proper wheel alignment. Without rings, vibration on the steering wheel is inevitable, even if the bolts are tightened tightly.
What to do if the markings are erased or unreadable?
If the numbers cannot be deciphered, you will have to measure the parameters manually. The bolt pattern and diameter can be calculated using formulas or using a special template (PCD ruler). It is extremely difficult to accurately measure the offset and width without removing the rim and special equipment, so in such cases it is better to contact a specialist at a tire center.
Does the country of origin of the disc affect the labeling?
The country of origin does not change the labeling logic, since the standards (ISO, JWL, TÜV) are unified. However, Japanese wheels are often marked JWL/VIA, European ones are TÜV, and Chinese ones may have less clear engraving or use their own load designation standards. Visually the line will look similar.
Is labeling required by law?
Yes, according to technical regulations, wheel rims must have markings that allow their parameters to be identified. The absence of markings or its unreadability may cause a refusal to pass a technical inspection, since the inspector will not be able to Verify that the wheels comply with safety requirements.