Decoding of wheel disc designations

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An attempt to install a disc with an inappropriate diameter of the central hole or the wrong number of bolts leads to the beating of the steering wheel and the destruction of the hub after a couple of thousand kilometers. That is why the correct decoding of the designations of wheels is a critical step before buying new components. Mistakes in setting parameters, such as PCD or ETIt can cost not only money, but also safety on the road.

Each number or letter on the inside of the product carries specific technical information, the neglect of which is unacceptable. Factory markings contain all the necessary data on geometry and load capacity, allowing you to accurately determine compatibility with your car. Let’s discuss in detail what lies behind each symbol and how to avoid fatal mistakes when choosing.

⚠️ Note: Using discs with parameters different from the factory specifications of the car can result in loss of warranty and road accidents.

Basic parameters: diameter, width and construction

The first thing that the driver pays attention to when visually inspecting or choosing in the catalog is the diameter and width of the rim. These parameters are denoted in inches and are usually separated by the symbol "x", for example, 7.5x17. The number 17 indicates the landing diameter, which must strictly correspond to the size of the tire, otherwise installation will be impossible or dangerous. The width of 7.5 inches determines the profile of the rubber used and affects the stability of the car in corners.

The rim design also has a value and is denoted by letter codes such as J, B or D. For passenger cars, the most common profile Jwhich characterizes the shape of the rim edge. The shape of the edge depends on how tightly the tubeless tire will sit and how reliably it will hold pressure at lateral loads.

rim-side shapes

There are different profiles of edges (J, JJ, B, D, K), each of which is designed for specific types of tires and loads. The JJ profile is often found on SUVs and has a steeper bend, which improves tire fixation at low pressure.

Blogging (PCD) and number of fastening holes

The most critical parameter, which does not allow even minimal deviations, is PCD Pitch Circle Diameter is the diameter of the circle along which the centers of the fastening holes are located. The marking looks like two digits separated by the “x” sign, for example 5x112. The first digit indicates the number of holes (usually 4 or 5 for passenger cars), and the second is the diameter of the circle in millimeters.

The discrepancy even 1-2 mm in the diameter of the chatter will lead to the fact that the disc will be loosely attached to the hub. As a result, when moving, a beat will occur, the bolts will begin to unscrew spontaneously, which is guaranteed to end with the wheel being separated at speed. Some manufacturers allow the use of universal disks with additional holes, but you can not rely on this without consulting an engineer.

• 🔩 4x98 is a common standard for VAZ cars and some Fiat models.
• 🔩 5x112 – typical of Mercedes, Volkswagen, Audi and many premium brands.
• 🔩 5x114.3 is the most popular standard for Japanese and Korean cars (Toyota, Honda, Kia).
• 🔩 6x139.7 – often found on large SUVs and pickups (UAZ, Mitsubishi Pajero).

Disk Departure (ET) and its Effect on the Suspension

Parameter ET (Einpress Tiefe) or disk departure indicates the distance between the vertical plane of symmetry of the wheel and the plane of application of the disk to the hub. It is measured in millimeters and can be positive, zero or negative. For most front-wheel drive cars, a positive departure is characteristic, when the mount is shifted outward relative to the center of the disk.

The change in departure relative to factory recommendations changes the shoulder of the run-in and the load on the hub bearings. Too small a flight (the disc strongly sticks out) increases the load on the suspension and can lead to the wheel touching the arches when turning or compressing. Too large a flight (the disc is sunk deep) can cause contact of the inner part of the disc with brake calipers or suspension elements.

Central Hole (DIA) and Hubs

Diameter of the central opening, marked as DIA, D or HUBIt should correspond exactly to the diameter of the landing burtic on the hub of the car. This value is measured in millimeters and is critical for the wheel's centering. If the hole in the disk is smaller than the protrusion on the hub, the disk simply will not wear.

In cases where the disk is universal and has a hole larger than necessary, special transition rings (sprists) are used. They allow you to install a disk with a large DIA on a car with a smaller landing diameter. However, using low-quality rings or installing them in a technology-disrupted manner can lead to wheel imbalance and vibrations.

Parameter	Designation	Unit of measurement	Criticism
Diameter of the central hole	DIA / HUB	mm	High (need rings)
Bluster	PCD	mm/number	Critical (no options)
Flight out	ET / Offset	mm	High (tolerance ± 5 mm)
Rim width	J / Width	inches	Medium (affects the tire profile)

Load indices and seasonal restrictions

Each disk has a maximum permissible load, denoted as LOAD or simply a number in kilograms/pounds (e.g. 690 kg). This parameter cannot be ignored, especially for crossover and commercial vehicle owners. The total load on four wheels should cover the full weight of the equipped car with passengers and cargo.

Also on disks are often found markings of seasonality. A snowflake sign against a mountain background indicates that the disc has been tested at low temperatures and retains strength in winter. Casting discs without such markings can become brittle in severe frost, which will increase the risk of cracks from impacts on the ice edges or hidden irregularities under the snow.

Additional markings and quality standards

In addition to geometric dimensions, various abbreviations can be found on products indicating quality standards and production methods. Marking TÜV It is a certificate of compliance with German safety standards, which is one of the most stringent certificates in the world. Japanese standard JWL The Japanese Wheel Light alloy also guarantees high reliability and JIS compliance.

The inside often indicates a production date, which can be embossed as a week and a year (e.g. 24/23 – 24th week of 2023). This is important because the life of alloy wheels, even when perfectly stored, is limited. Older discs may have microcracks in the metal structure, invisible to the eye, but dangerous during operation.

⚠️ Warning: Buying discs without quality certificates (TÜV, VIA, JWL) or with questionable marking of the country of origin carries the risk of alloy destruction.

Frequently Asked Questions (FAQ)

Can I put discs with a PCD 4x100 on a hub 4x98?

Theoretically, the 2mm difference seems negligible, and some drivers practice such a setup using eccentric bolts. However, this creates an uneven fit, which leads to rapid wear of the fastener, beating the steering wheel and potential wheel detachment. Experts categorically do not recommend without serious engineering improvements.

What does SAE marking on disk mean?

abbreviation SAE This is the standard of the Society of Automotive Engineers. This is an American standard that is often found on discs produced for the US market. It guarantees certain strength characteristics and methods of testing products.

How to find out the departure of the disk if the marking is erased?

Visually, it is impossible to determine the exact departure (ET). This requires a specialized measuring instrument or formula that requires knowledge of the distance from the landing plane to the inner elements of the disk. It is best to contact a specialized tire center, where the parameter is measured accurately.

Does the width of the disk affect fuel consumption?

Yes, installing wider discs increases the tyre-road contact spot, which increases rolling resistance. In addition, wide discs are often heavier than standard ones, which increases unsprung mass and rotational inertia, indirectly affecting the engine appetite.