Have you ever noticed a mysterious abbreviation ET on the back of the rim and ever wondered what it means? This parameter is one of the most important when choosing wheels, but many car owners either ignore it or do not understand how it affects the behavior of the car. Meanwhile, wrong disc ejection (ET) can lead to accelerated suspension wear, uneven tire wear, and even loss of control at high speeds.

In this article we will figure out what it is ET in practice - without complex formulas, but with specific examples and consequences of errors. You will learn how to measure the offset yourself, what values ​​are considered acceptable for your car, and why even a small deviation from the factory parameters can result in expensive repairs. We’ll also debunk the myths about “universal” discs and show how manufacturers sometimes cheat with labeling.

If you are planning to buy new wheels or just want to understand why your car “floats” on the road after replacing the wheels, read on. We've collected all the critical information in one place, including compatibility tables and warnings about common errors.

What is ET on disks: a simple explanation

Parameter ET (from German EinpressTiefe) denotes disc offset - the distance between the mating plane of the disk (the part that is pressed against the hub) and the imaginary central axis of the disk. It is measured in millimeters and can be:

  • 🔹 Positive (for example, ET45) - the mating plane is shifted outward relative to the center.
  • 🔹 Zero (ET0) - the plane coincides with the axis.
  • 🔹 Negative (for example, ET-15) - the plane is recessed inward.

Simply put, ET determines how much the disk will “stick out” or “sink” relative to the wheel arch. This setting directly affects:

  • 🔧 Load on wheel bearings (too large an overhang wears them out faster).
  • 🔧 Suspension operation (incorrect ET changes the rolling arm, which leads to uneven wear of the shock absorbers).
  • 🔧 Controllability (the car may “scour” along the road or take turns poorly).

Important: Even if the disc physically fits on the hub, this does not mean that its ET fits your car. The manufacturer calculates the reach taking into account the weight of the car, suspension stiffness and steering kinematics.

📊 Have you ever paid attention to the ET parameter when purchasing disks?
Yes, I always check
Sometimes, if I remember
No, I didn't know it was important
I trust the seller in the store

How to measure ET yourself: step-by-step instructions

If the markings on the disk are erased or you buy a used version, the offset can be measured manually. You will need:

  • 📏 Ruler or caliper (more precisely).
  • 🪛 Square (or any object with a right angle).
  • 📝 Note paper.

Algorithm of actions:

  1. Place the disc on a flat surface face down (so that the mating plane is on top).
  2. Attach the square to the rim of the disc and measure the distance from the surface to the mating plane (parameter A).
  3. Turn the disk over and measure the depth of the well (parameter B) - the distance from the mating plane to the inner edge of the rim.
  4. Calculate the offset using the formula: ET = (A + B)/2 – B.

Example: if A = 120 mm, and B = 100 mm, then ET = (120 + 100)/2 – 100 = 10 mm.

Make sure the disc is clean and not warped

Use a precise tool (calipers are preferable to rulers)

Measure parameters A and B at least 2 times for accuracy

Check the result with the acceptable values for your car model-->

⚠️ Attention: On some disks (especially cast ones), the mating plane may not be perfectly flat due to technological protrusions. In this case, measure the distance to the main plane, ignoring small irregularities.

Permissible deviations ET: when can you “deviate” from the standard

Car manufacturers always indicate recommended departure for disks (for example, ET35–ET45 for Volkswagen Golf). But what if you liked a disc with a slightly different option? Here are the key rules:

Deviation ET (mm) Consequences Is it permissible?
±2 mm Invisible to the suspension, slight visual imbalance possible ✅ Yes
±5 mm Accelerated wear of wheel bearings (by 10–15%), vibrations are possible at speeds >120 km/h ⚠️ Highly undesirable
±10 mm or more Severe suspension imbalance, car “pull” to the side, risk of damage to arches ❌ No
Negative ET (if not specified by the factory) The disc protrudes beyond the arch, there is a high risk of damage when driving over uneven surfaces ❌ No

Exceptions:

  • 🚗 On some SUVs (for example, Toyota Land Cruiser 200) it is possible to install disks with ET10–ET25 instead of standard ET25 to increase the track.
  • 🚗 On sports cars (for example, BMW M3) sometimes they install wheels with a shorter offset to improve stability, but this requires modifications to the suspension.
⚠️ Attention: If you are installing drives with non-standard ET, be sure to check roll-in shoulder (distance between the center of contact of the tire with the road and the steering axis of the wheel). Changing it leads to heavier steering and uneven tread wear.
What is rolling leverage and why is it important?

The rolling shoulder is the distance between the point of contact of the tire with the road and the projection of the wheel's turning axis onto the road surface. With proper ET, this shoulder is minimal, allowing for easy handling and even tire wear. If the disc overhang is too large or small, the shoulder increases and the following problems occur:

- The steering wheel becomes “heavy” (especially at low speeds).

- When braking or accelerating, the car may “nod” or squat.

- The load on the steering rack and tips increases, which leads to their premature failure.

Consequences of incorrect ET: from vibrations to accidents

Many car owners mistakenly believe that the main thing is that the disc fits on the hub, and the offset can be adjusted with spacers. In practice, even a small deviation from the norm leads to serious problems:

1. Accelerated wear of the suspension

  • 🔴 Wheel bearings fail 2–3 times faster (with ET, different from the standard by 5–10 mm).
  • 🔴 Shock absorbers operate at the wrong angle, leading to oil leaks and loss of efficiency.
  • 🔴 Suspension arms experience increased stress, especially on rough roads.

2. Deterioration in controllability

  • 🔴 The car “floats” on the road, especially at high speeds (due to changes in wheel alignment).
  • 🔴 When braking, jerks to the side are possible (uneven distribution of braking forces).
  • 🔴 Braking distance increases due to improper weight distribution.

3. Tire problems

  • 🔴 Uneven tread wear (for example, a “sawtooth” pattern on the inside or outside).
  • 🔴 Increased risk of aquaplaning due to improper contact patch.

Critical case: on vehicles with rear multi-link suspension (e.g. Mercedes E-Class W212) incorrect ET can lead to deformation of the levers after 10–15 thousand km.

💡

If, after replacing the disks, you notice that the car has become worse on the road or the steering wheel vibrates at speeds of 100+ km/h, first check the ET compatibility. Often the problem is solved by installing spacers (but this is a temporary solution - it is better to choose the right wheels).

How disc manufacturers cheat with ET markings

There are discs on the market with double marking (for example, ET35/45), which misleads buyers. Let's figure out what this means and how not to run into a fake.

Three common tricks:

  1. "Universal" discs with ET range (eg ET20–ET40). In fact, this means that the disk can be installed on different cars, but only with spacers. Without them, the flight will be incorrect.
  2. Fake markings on replicas of famous brands (for example, BBS or OZ Racing). Often these discs have an ET value that does not correspond to actual measurements.
  3. Tuning wheels with reduced ET (for example, ET-12 for VW Golf, where is the standard ET35–ET45). Sellers position them as “sports”, but without modifications to the suspension they are dangerous.

How to check authenticity:

  • 🔍 Check the labeling with the official catalog of the manufacturer (for example, on the website Ronal or AEZ).
  • 🔍 Check the weight of the disc - fakes are often 10-15% lighter than the originals.
  • 🔍 Pay attention to the casting quality: there are no pores, chips or uneven coating on the original discs.
⚠️ Attention: Discs with markings are often found on the market ET0, which sellers pass off as “universal”. In fact, such a reach is only suitable for some American pickup trucks (for example, Ford F-150) and is rarely compatible with European or Asian cars.

Disc offset (ET) directly depends on its width. For example, if you install a wider disk (for example, instead of 7J take it 8.5J), then to maintain the factory suspension geometry you will need reduce ET.

Formula for calculating the new offset when changing the width of the rim:

New ET = Old ET – (New width – Old width) / 2

Example: if your car has wheels 7J ET40, and you want to put 8J, then:

New ET = 40 – (8 – 7) / 2 = 39.5 ≈ 40 mm (round to the nearest standard value).

However, there are nuances:

  • 🔹 On front-wheel drive cars (for example, Skoda Octavia) An increase in rim width of more than 1.5 inches requires an ET adjustment of 5–7 mm.
  • 🔹 On rear-wheel drive (for example, BMW 5 Series) you can afford wider rims with lower ET, but this will increase the load on the bearings.
  • 🔹 On all-wheel drive crossovers (for example, Subaru Forester) A change in wheel width of more than 2 inches may require a wheel alignment adjustment.

Important: when increasing the width of the disk it is also necessary:

  • 🔧 Install tires with a smaller profile (to maintain the outer diameter of the wheel).
  • 🔧 Check the gaps between the tire and the arch (especially when the steering wheel is turned completely).
💡

When selecting wheels, first determine the width, and then adjust the ET. Never change the offset “by eye” - even a difference of 3–5 mm can critically affect the life of the suspension.

Below is a table with acceptable offset values for common cars. The data is relevant for standard configurations (excluding tuning modifications).

Make and model Standard ET (mm) Allowable range ET (mm) Notes
Volkswagen Polo (2015–2023) 38–45 35–48 For versions with 6J and 6.5J wheels
Toyota Camry (XV70, 2017–present) 40 37–45 For 7J wheels. On hybrid versions ET is strictly 40
Hyundai Solaris (2017–2023) 46–52 43–55 Depends on the engine: 1.4L - ET46, 1.6L - ET52
Lada Vesta (all generations) 35–40 30–45 For 6J wheels. On versions with ABS ET strictly 38–40
Ford Focus (3rd generation) 50–55 47–58 For 6.5J–7.5J discs. On ST versions ET is lower (42–48)

For an accurate selection, always check with:

  • 📄 Operating manual your car (section "Wheels and Tires").
  • 📄 Disc manufacturer catalogs (for example, Alutec or Kosei).
  • 📄 Online selection services (for example, Diski.ru or KolesaDarom.ru).
⚠️ Attention: On some cars (for example, Audi A4 B9) permissible ET depends on the drive type: for quattro it is strictly fixed (for example, ET43), and for front-wheel drive versions may vary (ET38–ET45).

FAQ: Frequently asked questions about ET on discs

Is it possible to install wheels with ET different from the factory one if they fit on the hub?

No, you can't. Even if the disc physically seats on the hub, incorrect offset changes the load on the suspension and steering. For example, on Kia Rio factory ET - 46–52 mm. If you install disks with ET35, then:

  • The load on the wheel bearings will increase (they will fail after 20–30 thousand km instead of 100 thousand km).
  • Directional stability will deteriorate at speeds >100 km/h.
  • Tires will wear unevenly (especially the inner edge).

Exception: if the difference in ET is compensated by spacers exact thickness and a professional wheel alignment was done.

Which ET is better for tuning: positive or negative?

It depends on the purpose:

  • 🔧 Negative ET (for example, ET-12) visually widens the track, making the car wider and more aggressive. Suitable for cruising and drifting, but:
    • Increases the load on the suspension.
    • It can hit the arches when the steering wheel is turned completely.
    • Requires installation of arch extensions (on civilian cars).
  • 🔧 Positive ET (for example, ET45) retains factory geometry, but limits the choice of wide wheels.

Optimal for everyday driving factory ET or deviation no more than ±3 mm. For track or off-road use, you can experiment, but only with a modified suspension.

What happens if you install wheels with ET 10 mm smaller than the factory one?

The consequences depend on the car model, but in most cases:

  1. The wheels will protrude beyond the arches (risk of damage when driving over uneven surfaces or parking near curbs).
  2. The load on the steering rack and tips will increase (the steering wheel will become “heavy”).
  3. On front-wheel drive cars (for example, Renault Duster) this will lead to accelerated wear of the CV joints.
  4. At speeds >120 km/h, vibrations may occur due to alignment imbalance.

Example: on Toyota RAV4 factory ET - 45 mm. If you install disks with ET35, the wheel will move outward by 10 mm, which will lead to:

  • Reducing the life of shock absorbers by 30–40%.
  • There is a risk of the tire hitting the arch when turning completely.
Can ET be changed using spacers?

Yes, spacers allow you to adjust the offset, but with reservations:

  • ✅ Acceptable use spacers up to 5 mm thick (for example, to compensate for the difference between ET40 and ET35).
  • ⚠️ Undesirable install spacers thicker than 10 mm - this increases the load on the hub and can lead to its deformation.
  • ❌ Prohibited use spacers on cars with aluminum suspension arms (for example, Audi A6 C7), since this leads to their accelerated corrosion.

Important: after installing the spacers necessarily do a wheel alignment and check the tightness of the hub bolts after 500 km.

Where can I find the acceptable ET for my car?

Sources of information (from most reliable to least):

  1. Factory manual (section "Wheel Alignment" or "Technical Data").
  2. Sticker on the door pillar (sometimes disk parameters are indicated there).
  3. Manufacturer's official website (in the "Technical Specifications" or "Accessories" section).
  4. Disk databases:
    • WillTheyFit.com (allows you to compare the compatibility of disks of different models).
    • Diski.ru/catalog (catalog with filters by car brand).
  • Owner forums (for example, Drive2.ru), but the data there needs to be double-checked.

    • ⚠️ Be careful: on some sites (for example, in advertisements for the sale of discs) may be indicated incorrect ET values. Always check with official sources.