Searching for information about the geometry of wheels often turns into a quest, especially when the markings have erased on old stampings, and there is no documentation at hand. Disc launchET or OFFSET is a critical parameter that affects the stability of the vehicle and suspension wear. Errors in the selection can lead to the fact that the wheel will start to touch the arch or, conversely, the hub will be overloaded.
In most cases, data can be found directly on the product itself, in the technical documentation for the car or in specialized compatibility tables. Wrong takeoff It is able to shift the center of gravity of the wheel, which will negatively affect handling. That is why it is important to understand where to look for these figures and how to interpret them correctly.
There are several proven ways to get accurate data, from visual inspection to using online manufacturers directories. Below we will discuss each method in detail so that you can be sure of the correct choice of components for your vehicle.
Marking on the inside of the disc
The fastest and most reliable way to find out the departure parameter is a careful inspection of the disk itself. Manufacturers are required to apply technical information to the inside of the product, most often on the spokes or the back of the rim. Look for an acronym ET or OFFSET, followed by a numerical value, such as ET35 or ET45.
This figure indicates the distance in millimeters between the plane of attachment of the disc to the hub and the vertical axis of symmetry of the wheel. If the plane of attachment is shifted outward relative to the center, the departure is positive, if inward - negative. For most cars, it is a positive departure.
⚠️ Warning: Never focus on the appearance of the disk. Two externally identical wheels may have different hub geometry, which will lead to installation problems.
Sometimes, labeling can be hidden under a layer of dirt, paint, or corrosion, especially on old stamped discs. In such cases, it is recommended to clean the metal area with fine sandpaper to show the knocked out figures. Be careful not to damage the metal structure and not to disturb the balance.
If the marking is erased completely, measure the departure with a rod: add the depth of the disk and the distance from the landing plane to the edge of the rim, then divide in half and subtract the distance from the edge to the plane of the attachment.
Data search in technical documentation
The official source of truth is always the same. manual your car. In the section devoted to the technical characteristics or replacement of wheels, the manufacturer indicates the standard dimensions of the discs and tires. There you will find recommended parameters, including diameter, rim width and desired departure.
If the paper manual is lost, information can be found electronically on the website of the car manufacturer. Often the data are duplicated on a special sticker located on the body rack on the driver's door side, on the gas tank hatch or in the glove compartment. This sticker also indicates tire pressure for different loading modes.
The documentation may indicate several size options for different configurations or markets. It is important to choose the parameters that correspond to your engine model and suspension type. Use of discs with inappropriate offset This may cause the vehicle to fail a technical inspection.
- 🚗 Find the sticker on the central pillar of the body (from the driver's side).
- 📖 Open the "Technical Data" section in the service book.
- 💻 Check the electronic version of the manual on the brand website.
- 🏷️ Note the VIN sign, sometimes the data is duplicated there.
Use of online catalogs and compatibility tables
Modern technologies allow you to find out the departure of the disk without getting up from behind the computer. There are many specialized websites and online directories that have a database of parameters for thousands of car models. It is enough to enter the brand, model, year of release and modification to get a full list of suitable sizes.
However, it is worthwhile to be careful and double-check the data from unverified sources. The automotive industry knows many cases when the same model in different years of production changed the design of the suspension, and therefore the requirements for the wheels. Online directories convenient, but not always take into account regional features or restylings.
For accurate selection, it is better to use official catalogs of disk manufacturers, such as: K&K, SKAD foreign brands, BBS and OZ Racing. Their sites often have a car selection feature, where compatible parameters are guaranteed.
| Parameter | Designation | Unit of measurement | Where to find |
|---|---|---|---|
| Diameter. | R | Inches. | On the side of the tyre |
| Rim width | J | Inches. | Inside the disk |
| Flight out | ET / OFFSET | Millimeters. | Disk Spokes / Documentation |
| PCD | Number x Diameter | Millimeters. | Central part |
What is PCD and why is it important?
PCD (Pitch Circle Diameter) is the diameter of the circle on which the mounting holes are located. Even if the departure and diameter match, a PCD discrepancy of 1-2 mm will make the installation impossible or dangerous.
The impact of departure on handling and suspension
The departure parameter directly affects the distribution of loads in the suspension nodes. When changing the staffing value ET The shoulder of the wheel is shifted, which changes the nature of the car’s behavior on the road. Increased departure (wheel goes deeper into the arch) can cause the calipers or suspension elements to touch.
Reducing the departure (the wheel protrudes outward) visually expands the track and makes the car more stable in cornering, but at the same time increases the load on the hub bearings. BearingsThose that are not designed for such loads may fail significantly earlier than the deadline. In addition, protruding wheels quickly pollute the sidewalls of the body.
⚠️ Attention: The permissible deviation from the standard departure is usually ± 5 mm. Exceeding this value requires mandatory consultation with an engineer or a specialist tuning studio.
Also, it is worth considering that the change in departure changes the readings of the speedometer and the operation of stabilization systems (ESP, ABS), if they are tied to data on the rotation of the wheels. In some cases, the system may perceive the change in geometry as an emergency situation and limit engine power.
Deviation of departure more than 5 mm from the standard value creates a critical load on the hub bearing and can lead to its rapid destruction.
Features of selection for cast and forged discs
When choosing alloy wheels, the departure situation becomes even more important, since the shape of the spokes and internal geometry often do not allow the use of the parcel rings or change the settings. Cast discs have a strictly defined design, and an attempt to install a disc with an inappropriate departure can lead to the needles resting in the brake caliper.
Forged wheels, having high strength, often allow slightly larger variations in settings, but here there are strict rules. Forging manufacturers often specify the range of valid departures for a particular disk model. Ignoring this data can cause the disk to break up when it enters the hole.
If the central hole is larger than the normal one, centrical rings are used, which also affect the overall geometry of the wheel assembly.
- 🔨 Forged discs are stronger, but require accurate compliance with parameters.
- 🎨 The design of spokes cast discs may limit the choice of departure.
- ⚙️ Check the gap between the spokes and brake mechanisms.
- 📏 Use center rings with a large hub diameter.
☑️ Checking before buying discs
Frequent errors in determining parameters
One of the most common mistakes is the confusion between inches and millimeters. The departure is always measured in millimeters, while the diameter of the disk is in inches. Trying to substitute an inch value in a calculation formula or a compatibility table will lead to disastrous results.
Another mistake is to ignore the double marking. Some discs, especially those made in the United States or intended for different markets, may be double-marked or specific. Always double-check the data from multiple sources if the labeling seems strange or incomplete.
Also, drivers often forget that the departure is not the distance from the edge of the disk to the hub, but the distance from the plane of the mount to the geometric center. Misunderstanding This term leads to erroneous calculations when installing pads or choosing rubber.
Can I use the sleeves to change the flight?
The use of slots is permissible if they are made of a durable material (for example, aviation aluminum) and have the correct design. However, the shears increase the load on the hub and may require replacement of the regular bolts with longer ones. Safe use of paddles up to 20 mm thick, provided that the rest of the geometry of the wheel is normal.
Does the flight affect fuel consumption?
Yes, the departure change affects the aerodynamics of the car and rolling resistance. Protruding wheels create greater aerodynamic drag, which can slightly increase fuel consumption. In addition, changing the shoulder of the run-in may require great effort to rotate the wheel, which will also affect the economy.
What to do if the desired departure is not on sale?
If there is no disk with a perfect departure, you can consider using slots or, in rare cases, disks with the closest parameter (within a tolerance of ± 5 mm). Buying a disc with a very different departure "at will" is categorically not recommended, since this is a matter of traffic safety.