Disc ejection (or CO - hole center) is one of the key parameters that determines how the wheel will “sit” on the car hub. An error in the selection of the offset, even by a few millimeters, can lead to premature wear of the bearings, uneven wear of the rubber, or even the wheel hitting the arch when turning. At the same time, many car owners confuse CO with other disk parameters, such as PCD (bolt pattern) or DIA (diameter of the central hole).

In this article, we will look at what disc offset is in practice, why it cannot be ignored when buying new wheels, and most importantly, how to independently measure or find out the CO for your car. You will learn about hidden markings on disks, online databases of manufacturers, and even “folk” methods using improvised means. And at the end - answers to frequently asked questions that will help you avoid common mistakes.

What is CD (disc offset) and why is it important?

Disc offset (ET, from German EinpressTiefe) is the distance between the plane of attachment of the disk to the hub and the imaginary central axis of the disk. It is measured in millimeters and can be:

  • 🔹 Positive (for example, ET45) — the mounting plane is moved outward relative to the center;
  • 🔹 Zero (ET0) — the plane coincides with the center;
  • 🔹 Negative (ET-15) - the plane is recessed inward.

Depends on departure load on suspension and steering. For example, a disc with a smaller ET (more "bulged") moves the wheel outward, increasing the track width. This may improve cornering stability, but at the same time increases the risk of the wheel hitting the fender liner. The opposite situation - a disk with a large ET ("recessed") - narrows the track, which is sometimes used in tuning to visually "sink" the wheels in the arches.

⚠️ Attention: A change in offset by more than ±5 mm from the factory value requires wheel alignment adjustment. Otherwise, the rubber will be “eaten up” unevenly, and the suspension will receive additional load.

Where to look for the CO on the disk itself: decoding the markings

The most reliable way to find out the offset is to look at the markings on the inside of the disk. It is usually applied by engraving or etching and contains a full set of parameters. We are looking for a combination ETXX, where XX is the offset value in millimeters. For example:

  • 📌 ET35 — offset 35 mm;
  • 📌 ET0 — zero departure;
  • 📌 ET-20 — negative offset (-20 mm).

The marking might look like this: 7.5Jx17 H2 5x112 ET45 DIA66.6. Here:

  • 🔧 7.5Jx17 — width and diameter of the disk;
  • 🔧 H2 — number of humps (protrusions for tubeless tires);
  • 🔧 5x112 - bolt pattern (PCD);
  • 🔧 ET45 — departure;
  • 🔧 DIA66.6 - diameter of the central hole.
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If the markings are worn out or missing, try cleaning the disc with a wire brush - often the data is written under a layer of dirt or paint.

On Chinese or budget disks, the markings may be applied with paint, which wears off over time. In this case it will help documentation on disk (if preserved) or contact the seller indicating the disk model.

How to measure disc offset yourself (3 methods)

If there is no marking or you doubt its accuracy, the offset can be measured manually. For this you will need:

  • 📏 Ruler or caliper (more precisely);
  • 📐 Square or straight slats;
  • 🧲 Magnet (optional, for finding the mounting plane).

Method 1: Measure with wheel installed

  1. Place the rack against the rim of the disc so that it touches the edges (as shown in the photo below).
  2. Measure the distance from the rack to the plane where the disk is attached to the hub (A).
  3. Turn the wheel over and measure the distance from the rack to the inner edge of the rim (B).
  4. Departure is calculated using the formula: ET = (B - A)/2 + A.

Method 2: Measuring the removed disc

Place the disc on a flat surface with the outer side facing down. Place a ruler under the edge of the rim and measure the height (H). Then turn the disk over and measure again. Departure is calculated as ET = (H1 - H2)/2.

Method 3: Using a caliper

This method is more accurate, but requires skill. Measure the distance from the mounting plane to the inner edge of the disk (X) and to the outer edge (Y). Then use the formula: ET = Y - (D - X), where D — disk width in millimeters.

Prepare a flat surface without slopes|Clean the disc from dirt and dust|Use a precise tool (calipers are preferable to a ruler)|Repeat measurements 2-3 times to check-->

⚠️ Attention: When measuring, keep in mind that even a small error (1-2 mm) can critically affect the selection of the disc. For example, departure ET45 and ET47 are visually indistinguishable, but the second disk may not be suitable for your car model.

Determining the central heating unit by VIN code or car model

If you haven't purchased the drive yet or want to check compatibility, the easiest way is to use the manufacturer's database. To do this:

  1. Find VIN code your car (usually it is indicated in the STS, on a plate under the hood or on the driver's door pillar).
  2. Enter it on one of the services:
    • 🔗 Wheel-Size.com (English, but with support for Russian brands);
    • 🔗 Wheels-Darom.rf (Russian-language catalogue);
    • 🔗 Official website of the disc manufacturer (for example, BBS, OZ Racing).
  • The search results will indicate the recommended offset (sometimes with acceptable deviations).

    • An alternative way is to use spare parts catalogs by car model. For example, on Exist.ru or Autodoc enter the make, model and year of manufacture, then go to the "Wheels" section. The system will show all compatible parameters, including CO.

    Car make Model Factory offset (ET), mm Permissible deviation, mm
    Volkswagen Polo (2018-2023) 38-45 ±3
    Toyota Camry V70 (2021) 40 ±2
    Lada Vesta (2015-2023) 35-40 ±5
    Hyundai Solaris (2020) 46-52 ±2
    BMW 3 Series (G20) 25-35 ±1

    Based on the recommendations of an official dealer|Independently using catalogs|I consult on forums|I trust the seller in the store|Another option-->

    Common mistakes when determining departure and how to avoid them

    Even experienced car owners sometimes make mistakes when dealing with disc slippage. Here are the most common of them:

    • 🚫 Confusing ET with PCD. Bolt pattern (PCD) is the location of the mounting holes (for example, 5x112), and offset is the displacement of the disk relative to the hub. Confusing them means buying a disk that simply won’t fit on the car.
    • 🚫 Ignore tolerances. For example, for Lada Granta factory offset ET35, but allowed ET38. Installing a disc with ET50 will lead to problems.
    • 🚫 Disc width is not taken into account. Departure ET45 on a disk wide 7J and 9J - these are different things! The wider the rim, the greater the influence of offset on wheel position.
    • 🚫 Trust “universal” drives. Discs labeled “Universal Fit” often have average parameters that are not suitable for a particular model.

    To avoid mistakes, always check the parameters with instruction manual your car or consult a tire specialist. Don't be too lazy to do it test installation one disc before purchasing a set - this will save time and money.

    What happens if you install a disk with the wrong offset?

    With low ET (the disk “sticks out”):

    - The load on the wheel bearing increases (risk of premature wear).

    - The wheel may touch the arch when turning or on uneven surfaces.

    - Controllability deteriorates at high speeds (yaw effect).

    If ET is too high (the disk is “recessed” inward):

    - Narrowing the track impairs cornering stability.

    - The wheel may touch the suspension elements or brake mechanisms.

    - Incorrect operation of ABS and exchange rate stability system (ESP).

    Departure specifics for tuned and sports cars

    Owners of sports cars or cars with modified suspensions often deliberately change the offset of the rims to improve appearance or handling. However, there are nuances here:

    • 🏎️ For lowered cars disks with negative offset (for example, ET-15) so that the wheel does not “rest” against the arch. But this requires widening the wheel arches or installing spacers (spacers).
    • 🏁 For drifting Sometimes wheels with minimal ET are used to increase track width and improve traction. However, this reduces the suspension life.
    • 🚗 For crossovers with increased ground clearance, the offset often remains standard, but the discs are taken wider (for example, instead of 7J install 8.5J with the same ET).

    Important: when tuning the departure, be sure to:

    1. Check gaps between the wheel and body/suspension elements at maximum steering angles.
    2. Correct wheel alignment after departure change.
    3. Consider bearing load - for example, on Subaru Impreza WRX departure ET55 standard, but upon installation ET35 a reinforced hub will be required.
    💡

    When tuning the offset, be sure to use spacers with centering rings, if the diameter of the central hole of the disk is larger than the hub hole. Otherwise, the wheel will “beat” when moving.

    Online calculators and mobile applications for calculating central heating

    If you are not sure of your measurements or want to check disk compatibility, use specialized services:

    • 📱 Wheel Fitment App (Android/iOS) - allows you to enter the disk parameters and check if it is suitable for your machine. There is a database of 10,000+ models.
    • 🖥️ Calculator at WillTheyFit.com — compares two sets of disks and shows how the offset will change when replaced.
    • 📊 Sergey’s Wheel Calculator (wheel-calc.ru) - visualizes the position of the wheel relative to the arch.

    An example of working with a calculator:

    1. Enter parameters standard disk (for example, 7Jx16 ET45).
    2. Specify parameters new disk (for example, 8Jx17 ET35).
    3. The service will show how many millimeters the wheel position will change and whether there will be any conflicts with the arch.

    Please note: online calculators give theoretical compatibility. For accurate results, always do physical fitting!

    FAQ: Answers to frequently asked questions about disc ejection

    Is it possible to install wheels with an offset different from the factory one?

    Yes, but with reservations. The permissible deviation is usually specified in the instruction manual (e.g. ±3 mm for Volkswagen or ±5 mm for Lada). Exceeding this range requires:

    • Checking the gaps between the wheel and the arch/suspension;
    • Camber adjustments;
    • Taking into account the increased load on wheel bearings.

    On sports cars (for example, BMW M3) sometimes they deliberately use a non-standard offset to improve handling, but this requires modifications to the suspension.

    What is the best offset for a lowered car?

    For lowered cars it is recommended:

    • Decrease ET (for example, with ET45 up to ET30), so that the wheel does not touch the arch;
    • Use narrow wheels (for example, 7J instead of 8J);
    • Install spacers (spacers) with centering rings;
    • Check ground clearance on a lift at maximum wheel turn.

    Example: on VAZ 2110 with a lowering of 50 mm, wheels are often installed with ET20-25 instead of standard ET35-40.

    What is “zero” offset (ET0) and what cars is it suitable for?

    Zero offset means that the disk mounting plane coincides with its central axis. Such disks are often used:

    • On SUVs (for example, Toyota Land Cruiser 200);
    • On sports cars with wide wheels (for example, Nissan GT-R);
    • On commercial transport (for example, Ford Transit).

    For passenger cars (for example, Hyundai Solaris) ET0 is usually not suitable - the wheel will protrude far beyond the arch.

    Is it possible to determine the offset from a photo of the disk?

    No, it is impossible to accurately determine ET from a photo, because:

    • The photograph is not to scale;
    • The offset depends on the width of the rim (e.g. ET45 on 7J and 9J visually will look different);
    • The shooting angle distorts the perspective.

    The only reliable way is marking on the disc or physical measurement.

    Where to buy wheels with non-standard offset?

    Discs with atypical ET can be found:

    • 🛒 B specialized stores (for example, K&K>, Replica Wheels for tuned cars);
    • 🌍 On foreign sites (for example, eBay, AliExpress - but be careful with the quality!);
    • 🔧 U local tuning studios, which make wheels to order;
    • 📦 On debriefings (for example, disks from Audi RS often have unique ETs).

    Before purchasing, be sure to check seller reviews and request certificate of conformity (especially for discs from China).