What is disk offset ET and why it needs to be counted

Disc offset (designation ET from German EinpressTiefe) is the distance between the mating plane of the disk and its central axis. The parameter is measured in millimeters and can be positive, zero or negative. For example, ET45 means that the disc protrudes inward by 45 mm relative to the center.

Why is this important? Incorrect offset changes the load on the wheel bearings, steering rack and suspension components. Even if the diameter and bolt pattern match, a disk with incorrect ET can lead to:

  • 🔧 Accelerated wear bearings and ball joints
  • 🚗 Deterioration in controllability (the car “floats” at speed)
  • 🛑 Harassment disc on the brake caliper or arch
  • ⚖️ Problems with passing maintenance (in Russia, a deviation of ±5 mm from the standard value is permissible)

Manufacturers calculate the reach taking into account the weight of the vehicle, the type of suspension and load distribution. For example, at Volkswagen Golf VII standard ET for disks R16 — ET51, and Toyota RAV4 — ET45. Even a slight deviation of ±10 mm can affect the life of the chassis.

📊Have you ever encountered problems due to discs not ejecting correctly?
Yes, there were vibrations at speed
Yes, the disc was rubbing against the caliper
No, I always selected according to parameters
I don't know what ET is

Formula for calculating disk offset ET

To calculate the departure yourself, use the formula:

ET = (X + Y/2) - Z

Where:

  • X — distance from the mating plane to the inner edge of the disk (measured with a ruler)
  • Y - total width of the disk (indicated in the marking, for example, 8J = 8 inches)
  • Z — distance from the mating plane to the hub (measured with a caliper)

Example: a disk has a width 8J (203.2 mm), X = 120 mm, Z = 65 mm. Then:

ET = (120 + 203.2/2) - 65 = (120 + 101.6) - 65 = 156.4 mm

However, in practice it is easier to use online calculators (for example, on sites DiskCalc.ru or Wheel-Size.com), where you just need to enter the parameters of the disk and vehicle. But if you buy a used disc without markings, manual measurement is the only option.

💡

When measuring Z (distance to the hub) use a caliper with a depth gauge - the ruler error can give an error of 2-3 mm, which is critical for ET.

How to measure disc offset without formulas (practical methods)

If the formulas seem complicated, there are two alternative methods:

  1. Comparison with standard disk

    Place the new and old disc on the hub, place a ruler against the rim and measure the difference in protrusion. For example, if a new disc protrudes 5 mm more, its ET is 5 mm less than stock.

  2. Using a template

    Cut out a template from cardboard along the contour of the old disk, place it on the new one and compare the position of the mating plane.

For accuracy use laser level or construction square. The main thing is to fix the disk on a flat surface (for example, on a table) and avoid distortions.

What should I do if the ET marking on the disc is erased?

Contact the seller for a certificate or product passport. On some discs, the offset is duplicated on the inside of the rim (shine it with a flashlight).

Permissible departure deviations: what the law and manufacturers say

There are no strict standards for ET in Russia, but there are recommendations:

Vehicle type Tolerance ET Consequences of exceeding
Cars (sedans, hatchbacks) ±5 mm Accelerated bearing wear
Crossovers/SUV ±3 mm Vibrations in the steering wheel, uneven tire wear
Sports cars ±2 mm Loss of directional stability
Freight/commercial ±7 mm Increased load on springs

Disc manufacturers (eg BBS, OZ Racing) allow a deviation of up to ±10 mm, but only if the disk certified for a specific car model. Otherwise, you risk losing your suspension warranty.

⚠️ Attention: On vehicles with multi-link suspension (for example, Audi A4 B8, BMW 5 Series F10) even a deviation of 3 mm can cause irreversible deformation of silent blocks.

Common mistakes when calculating ET and how to avoid them

Mistake #1: Ignoring disk width. Many people consider ET only from the mounting plane, forgetting that the width of the rim (e.g. 7.5J vs 9J) directly affects the final flight.

Mistake #2: Inaccurate measurements. Using a ruler instead of a caliper gives an error of up to 2 mm. For ET this is critical - a difference of 2 mm can lead to interference when the car is fully loaded.

Mistake #3: Disregarding spacers. If you are using spacers to widen the track, their thickness deducted from ET. For example, when ET45 and a 15 mm spacer, the actual offset will be ET30.

Check the standard ET for your model in the manual|Check the markings on the disk (ET, PCD, DIA must match)|Use a 3D visualizer (for example, on Wheel-Size.com) to check the gaps|Check the compatibility database (for example, DiskInfo.ru)-->

Let's look at real cases:

  1. Lada Vesta (standard disk 6J ET50)

    You bought the disc 7J with unknown ET. Measurements showed: X = 110 mm, Z = 60 mm. Width 7J = 177.8 mm.

    Calculation: ET = (110 + 177.8/2) - 60 = 108.9 mm. This disc is not suitable - deviation from standard ET50 will be +58.9 mm!

  2. Kia Rio 4 (standard disk 6J ET46)

    Disk 6.5J with markings ET42. The difference of 4 mm is within the tolerance, but the width has increased by 12.7 mm (with 6J up to 6.5J). This can lead to contact when the wheels turn out.

Critical error: on cars with a rear multi-link (for example, Skoda Octavia A7) decreasing ET by 10 mm increases the load on the levers by 20-30%. This leads to their deformation after 20-30 thousand km.

Online services and programs for checking ET

To quickly check compatibility use:

  • 🌐 Wheel-Size.com — database of 3000+ car models with visualization of gaps
  • 📊 DiskCalc.ru — ET calculator taking into account spacers and changed track
  • 📱 Application "Tuning Wheels" (Android/iOS) - scans the disk label and compares it with the database

How to work with Wheel-Size.com:

  1. Select the make, model and year of the car.
  2. Specify the disk parameters (diameter, width, PCD).
  3. The system will show the permissible ET range and warn of possible impacts.
⚠️ Attention: Online calculators do not take into account individual modifications suspension (for example, spacers for springs or modified lever geometry). After tuning, be sure to recalculate ET manually!
💡

Even if the online service shows "compatible", physically check the disc in a fully loaded vehicle (tank full, 4 passengers).

FAQ: Frequently asked questions about disc ejection

Is it possible to install a disc with ET0 on a car with a standard ET45?

No. A difference of 45 mm will radically change the load on the wheel bearings and can lead to their destruction after 5-10 thousand km. The maximum permissible deviation for passenger cars is ±5 mm.

Which ET to choose for a lifted SUV?

When lifting the suspension (increasing ground clearance), the offset should be less than staff by 5-15 mm (depending on the height of the elevator). This moves the wheel outward, compensating for the changed angle of the arms. For example, for Toyota LC200 after the lift +50 mm is optimal ET20-25 instead of the regular one ET35.

Does ET affect fuel consumption?

Yes, but indirectly. Incorrect offset increases rolling resistance (if the disc protrudes outwards) or overloads the bearings (if the UT is too positive). In both cases, fuel consumption can increase by 3-7%.

Can incorrect ET be corrected with spacers?

Theoretically yes, but:

  • Spacers thicker than 10 mm require extended bolts (standard ones may not withstand the load).
  • On vehicles with ABS, spacers can interfere with the sensors.
  • In Russia, the use of spacers not certified - this may cause denial of insurance payment in case of an accident.
Where is ET listed on the disk?

The offset is marked on the inside of the rim in the format ETXX (for example, ET45). On some discs it may appear as OFFSET XX. If there is no marking, look for it:

  • On the knitting needles near the central hole.
  • On the outer edge of the rim (you will have to remove the tire).
  • In the certificate or passport of the disc (if the disc is new).