If, when installing new rims, the wheel begins to touch the arch or suspension, and the steering wheel becomes “heavier” when cornering, the problem is due to an incorrectly selected parameter ET (disc ejection). This indicator, indicated on the back of the disc (for example, ET45), determines the distance from the mating plane to the central axis of the disk. Even a deviation of ±5 mm can cause the wheel to move inward or outward, which will affect handling, bearing wear and suspension life. For example, on Volkswagen Golf IV standard departure is ET38, and installing disks with ET20 will increase the load on the wheel bearing by 20–30%.

Reach is not just a geometric parameter, but a key safety factor. Non-compliance of ET with the manufacturer's recommendations changes the leverage of force application, causing the suspension to operate abnormally. In extreme cases this leads to loss of directional stability at high speeds or accelerated wear of rubber along the inner/outer edge. In this case, visually the disk can “sit” on the hub without problems, and the consequences will appear after 5-10 thousand kilometers.

What is ET offset on disks: technical definition

Disc offset (ET, from him. EinpressTiefe - “press-in depth”) is the distance between the mating plane of the disc (point of contact with the hub) and the imaginary central plane of the rim. It is measured in millimeters and can be:

  • 🔹 Positive (for example, ET40) - the mating plane is shifted forward relative to the center of the disk.
  • 🔹 Zero (ET0) - the planes coincide.
  • 🔹 Negative (for example, ET-15) - the mating plane is shifted back, the disk “sticks out” outward.

Most passenger cars use a positive offset (from ET20 up to ET50). For example, for Toyota Corolla E170 standard parameter - ET45, and for BMW 3 Series (E90) — ET34. Negative offset is typical for SUVs (e.g. Jeep Wrangler with ET-12.7) or tuned cars where the track needs to be widened.

How to measure ET offset yourself

1. Place the disc on a flat surface (with the mating surface facing down).

2. Measure the distance from the surface to the edge of the rim on one side (A).

3. Turn the disc over and measure the distance to the edge on the other side (B).

4. Departure ET = (A + B)/2 − B.

Important: offset is not related to wheel width or diameter. For example, disk 7.5Jx17 ET40 and 8.5Jx17 ET40 They have the same reach, but different widths. However, as the width increases, the ET often needs to be adjusted to keep the wheel within the arch.

What does ET departure affect: the consequences of a wrong choice

Deviation of the offset from the standard value changes the distribution of loads on the suspension and steering. Even if the disk physically fits onto the hub, the consequences can be critical:

ET deviation Consequences Examples of problems
ET less than normal (the disk “sticks out” outward) Increases the load on the wheel bearing and suspension arms Accelerated bearing wear (service life is reduced by 30–50%), vibration on the steering wheel
ET more than normal (the disk is “recessed” inside) Shifting the center of gravity of the wheel to the body, reducing the track Wheel touching the arch or shock absorber when turning, instability at speeds >120 km/h
ET = standard ±2–3 mm Tolerance for most vehicles Minimal impact on handling, possible uneven tire wear
ET differs by ±5 mm or more Critical change in suspension geometry Steering of the car to the side, uneven tread wear, risk of ball joint failure

For example, on Hyundai Solaris regular departure - ET46. Installing disks with ET35 (11 mm less) will result in:

  • 🔧 Increase the load on the wheel bearing by 25–30%.
  • 🔧 Shifting the tire contact patch outward, causing the outer edge of the tread to wear off 2 times faster.
  • 🔧 Possible contact of the wheel with the mudguard when the steering wheel is turned completely.
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Even if the disc is visually suitable in diameter and width, a discrepancy between ET by 5–10 mm can lead to suspension failure after 10–20 thousand km.

How to Determine the Allowable ET Reach for Your Vehicle

The standard offset is indicated in the technical documentation of the car or on a sticker in the doorway (next to the recommended tire pressure). Alternative sources:

  • 📄 Instructions for use (section “Wheels and Tires”).
  • 🖥️ Manufacturer's official website (for example, Toyota or Volkswagen provide data on models).
  • 🔧 Spare parts catalogs (for example, ETKA for VAG group vehicles or Elcats).
  • 📱 Mobile applications like Wheel-Size or TireSize Calculator.

If there is no data, use calculation formula: Acceptable ET = Stock ET ± (Width of new rim − Width of stock rim) / 2

For example, for Kia Rio 3 with standard disks 6Jx15 ET48 and tires 185/65 R15 when installing disks 7Jx15 allowable ET will be:

48 − (7 − 6)/2 = 47.5 (round up to ET48).

I use only standard parameters|I look at the disc manufacturer's recommendations|I trust the salesperson in the store|I use online calculators|I don't pay attention to ET-->

⚠️ Attention: Some disk manufacturers indicate in their catalogs “universal” models with the ET range (for example, ET35–45). Such wheels are only suitable for cars where the standard offset falls within this interval. For example, for Skoda Octavia A5 (regular ET38) disk with ET35–45 acceptable, but for Renault Duster (ET50) - no.

Is it possible to install wheels with a different offset ET?

Theoretically it is possible, but with strict restrictions:

  1. Deviation up to ±2 mm - acceptable for most cars without consequences.
  2. Deviation 3–5 mm - requires checking for wheel contact with the suspension or arch. Accelerated bearing wear is possible.
  3. Deviation more than 5 mm - not recommended. Exception: tuning with modification of the suspension (installation of spacers, change in the geometry of the levers).

Example: on Lada Vesta regular departure - ET35. Installing disks with ET30 (deviation −5 mm) will lead to:

  • 🔧 Increase in track by 10 mm (5 mm per side), which will affect handling.
  • 🔧 Increased load on external constant velocity joints (CV joints).
  • 🔧 Possible contact of the wheel with the plastic fender liner when turned completely inside out.

1. The gap between the wheel and the shock absorber/spring when the steering wheel is turned completely.

2. Distance from the inner edge of the disc to the brake caliper (must be ≥10 mm).

3. The behavior of the car at a speed of 100+ km/h (is there any wobbling of the rear axle).

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The exception is disks with zero departure (ET0), which are often used for tuning. They require installation spacers (aluminum or steel rings) to compensate for the difference. For example, for Subaru Impreza WRX with staff ET55 and disks ET0 55mm thick spacers will be required. However, this solution has disadvantages:

  • 🔹 The load on the hub and bearing increases.
  • 🔹 Extended bolts or studs may be required.
  • 🔹 Risk of “shooting” the wheel due to poor-quality spacer.

Common mistakes when choosing wheels based on offset ET

Even experienced car owners make mistakes that lead to problems with the suspension or tires:

✅ Check the standard ET offset in the vehicle documentation

✅ Make sure the new disc has the same center drill (DIA)

✅ Check PCD (bolt pattern) compatibility - for example, 4x100 is not suitable instead of 4x98

✅ Measure the gap between the future disc and the brake caliper (should be ≥5–10 mm)

✅ Visually assess whether the disc will protrude beyond the arch (especially with negative ET)

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Typical misconceptions:

  1. “If the disc fits on the hub, then the ET fits” - no, physical compatibility does not guarantee the correct geometry. For example, a disk with ET20 can sit on the hub Ford Focus with staff ET52.5, but this will cause the wheel to move outward by 16.25 mm to the side.
  2. "Wider rims always require less ET" - incorrect. Wheel width and offset are related, but are not interchangeable parameters. For example, on Audi A4 B8 standard wheels 7.5Jx17 ET43 can be replaced by 8Jx17 ET45 (wider, but with greater ET).
  3. “Spacers will solve all problems” - only if they are certified and installed correctly. Cheap spacers made of “soft” aluminum can become deformed, and incorrect tightening torque of the bolts will lead to “beating” of the wheel.

⚠️ Attention: On some vehicles (for example, Mercedes-Benz with the system 4MATIC or BMW xDrive) changing the ET offset can lead to malfunctions of the all-wheel drive. The electronics recognizes the change in geometry as a malfunction and activates emergency mode.

How to correct the consequences of an incorrect ET departure

If the wheels are already installed and problems are detected (vibrations, uneven tire wear, knocking), follow the algorithm:

  1. Diagnostics:
    • 🔧 Check the play in the hub bearings (jack up the car and rock the wheel).
    • 🔧 Inspect the tires for uneven wear (if the edge wears off on one side, there is a camber or ET problem).
    • 🔧 Test the car at a speed of 80–100 km/h: if the steering wheel “beats” or the car “drives”, immediately remove the rims.
  2. Temporary measures:
    • 🔧 If ET is less than standard, you can install spacers (but this is a half-measure).
    • 🔧 If ET is greater, check whether the wheel is catching on the suspension elements when fully turned.
  3. Final Solution:
    • 🔧 Replace the drives with models with the correct ET.
    • 🔧 If the discs are new and expensive, sell them and buy suitable ones (often stores go for exchanges).

⚠️ Attention: If you have driven more than 5 thousand km after installing disks with incorrect ET, be sure to check:

  • 🔧 Condition of the wheel bearings (listen for hum).
  • 🔧 Suspension geometry (the wheel alignment could “go away” due to wheel displacement).
  • 🔧 Integrity of CV joints (with negative ET they operate at an increased angle).

ET departure and tuning: when the rules can be broken

In tuning, the ET offset is often changed intentionally for:

  • 🔥 Track extensions (improved cornering stability).
  • 🔥 Wide rim settings (for example, ET20 instead of ET40 for disks 9.5J).
  • 🔥 Creating an aggressive appearance (“bulging” wheels).

However, this requires complex improvements:

Purpose of tuning Required Modifications Risks
Reducing ET for wide rims Installing spacers, replacing wheel bearings with reinforced ones, adjusting camber Accelerated wear of CV joints, increased load on levers
Increasing ET for recessed wheels Trimming arches, replacing shock absorbers with shortened ones Reduced stability when cornering, risk of the wheel hitting the suspension
Installing disks with ET0 Spacers 20–50 mm, extended bolts, reinforced hubs Increased risk of wheel “shooting off” in an accident

Example: on Nissan GT-R R35 often install disks with ET15–20 instead of the regular one ET40, but at the same time:

  • 🔧 Change the suspension arms to adjustable ones.
  • 🔧 Install spacers made of aluminum.
  • 🔧 Wheel alignment is corrected every 5 thousand km.
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Tuning with ET changes should be accompanied by increased suspension maintenance. For example, on sports cars, wheel bearings are changed every 30–40 thousand km (instead of 100 thousand km as usual).

FAQ: Frequently asked questions about ET crash on disks

Is it possible to install wheels with ET35 instead of ET45?

A deviation of 10 mm is critical. On most vehicles this will cause the wheel to move outwards by 10mm (5mm per side), increasing the load on the bearings and potentially causing the wheel to touch the arch. The exception is vehicles with wide arches (such as SUVs), but even then it is recommended to use spacers to compensate for the difference.

What is the best ET offset for a lowered car?

When the ground clearance is lowered, the ET offset should be closer to standard or even a little more (2–3 mm). Reducing ET when underestimating will lead to:

  • 🔹 Wheel touching wheel arch liners or shock absorbers.
  • 🔹 Deterioration in controllability due to a shift in the center of gravity.

Optimal: use disks with standard ET, but with a smaller diameter (for example, R16 instead of R17) to increase ground clearance.

Does ET affect fuel consumption?

Indirectly - yes. Increasing ET (the disc is “recessed” inward) increases the load on the suspension, which can increase consumption by 0.3–0.5 l/100 km. Reducing ET (disc "sticks out") increases air resistance, especially at high speeds, which also affects efficiency. However, the effect is less noticeable than from tire pressure or driving style.

Is it possible to drive with different ET offsets on the front and rear axles?

Absolutely not. Different offsets on the axles lead to:

  • 🔹 Unpredictable controllability (the car can “scour” along the road).
  • 🔹 Accelerated wear of the differential (in all-wheel drive vehicles).
  • 🔹 Uneven operation of ESP/ABS systems.

The exception is some sports cars (for example, Porsche 911), where the rear axle is wider than the front, but this is inherent in the design.

Which ET is suitable for wheels with bolts and nuts (for example, on a UAZ or Niva)?

For vehicles with wheel nuts (e.g. UAZ Patriot, Niva Chevrolet) ET offset must strictly correspond to the standard one. Deviations are unacceptable because:

  • 🔹 Nuts create a smaller contact area with the hub than bolts.
  • 🔹 Play in the connection with incorrect ET leads to “beating” of the wheel.

For UAZ regular ET usually ET58, for Niva Chevrolet — ET29 (before) and ET0 (back).