Have you ever wondered why some wheels fit your car perfectly, while others - even with the same diameter and bolt pattern - look "wrong"? Most often the problem lies in mysterious letters ET, which many car owners ignore when purchasing. This parameter, hidden on the back of the disk among other markings, actually determines how the wheel will “sit” relative to the hub - and not only the appearance, but also management security, suspension wear and even fuel consumption.

In this article we will look at what it is ET in disks (or disc offset), how to measure it correctly, what values are considered acceptable for your car, and what happens if you ignore this parameter. You'll also find out if you can install wheels with a different ET, how this will affect ride quality, and where to find the exact data for your model. Spoiler: even a difference of 5 mm can lead to premature wear of the wheel bearings or incorrect operation of the ABS.

What is ET on disks: decoding and physical meaning

Abbreviation ET (from German EinpressTiefe) is translated as “extrusion depth” and means disc offset - the distance between the mating plane of the disk (the one that is pressed against the hub) and the imaginary central axis of the wheel. It is measured in millimeters and can be:

  • 🔹 Positive (ET35, ET40) - the mating plane is shifted inside relative to the center of the disk. Such discs are “recessed” deeper into the arch.
  • 🔹 Zero (ET0) - the plane coincides with the central axis.
  • 🔹 Negative (ET-10, ET-20) - the plane is taken out outward, the disc protrudes beyond the arch (often used in tuning).

Simply put, ET shows how much the wheel will “stick out” or “hide” relative to the body. For example, if your car has a standard offset ET45, and you installed the disk with ET30, the wheel will move outward by 15 mm. This will not only change the appearance, but will also increase the load on the wheel bearings as the force arm (the distance from the center of the wheel to the fulcrum) will become greater.

📊 How do you usually choose wheels for your car?
By appearance
According to manufacturer's recommendations
By parameters (ET, PCD, diameter)
I buy used without inspection

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

If the markings on the disc are erased or you doubt their accuracy, the offset can be measured manually. You will need:

  • 📏 Ruler or caliper (more precisely).
  • 🪛 Square or even strip.
  • 📝 Note paper.

Algorithm of actions:

  1. Place the disc on a flat surface face down (matting plane up).
  2. Place the rack against the rim of the disc so that it touches the outer edges (see photo below).
  3. Measure the distance from the mating plane to the rail (X).
  4. Turn the disk over and measure the distance from the rack to the inner edge (Y).
  5. Calculate the offset using the formula: ET = (X + Y)/2 — Y.

Make sure the disc is clean and not deformed|Use an accurate tool (calipers are preferable)|Measure the X and Y distance at least 3 times for accuracy|Check the result with the table of acceptable values ​​for your model-->

Example: if X = 120 mm, and Y = 100 mm, then ET = (120 + 100)/2 - 100 = 110 - 100 = 10 mm. This means that the disc offset is equal to ET10.

⚠️ Attention: If you get a negative value when measuring, this is normal - such a disk has a negative offset (for example, ET-15). However, for most production cars, negative ET is not acceptable and is only used in sports or performance cars.

Permissible deviations ET: when you can install wheels with a different offset

Car manufacturers always indicate recommended departure in technical documentation. However, in practice, many car owners install wheels with a deviation of ±5 mm, and sometimes more. Is it really safe?

The answer depends on several factors:

  • 🚗 Suspension type: On machines with multi-link suspension (for example, Volkswagen Golf or BMW 3-series) even a small change in ET can lead to accelerated wear of silent blocks. While on cars with MacPherson strut suspension (for example, Lada Vesta or Renault Logan) the tolerances are slightly wider.
  • 🔧 Disc width: The wider the rim, the more critical the offset becomes. For example, on disk 8J a deviation of 5 mm will have a greater effect than 6J.
  • 🛠️ Availability of amplifiers: If the car is equipped reinforced wheel bearings or sports suspension, the tolerances can be slightly increased.
Deviation of ET from standard Consequences Recommendations
±2 mm Invisible to control, minimal suspension wear Acceptable without restrictions
±5 mm Slight change in steering effort, possible uneven tire wear Acceptable with regular suspension checks
±10 mm or more Significant deterioration in controllability, risk of hub failure, incorrect ABS operation Not recommended, only for tuning with suspension modifications
Negative ET (ET-10 and below) The wheel protrudes beyond the arch, there is a high risk of damage when driving over uneven surfaces Only for sports cars with wide arches

Example: if on Toyota Camry standard departure ET45, then the disk with ET40 will move the wheel outward by 5 mm. This will lead to:

  • 🔄 Increase the load on the wheel bearing by ~15%.
  • 🚗 Slight “weighting” of the steering wheel at high speeds.
  • 🔥 Faster wear of the outer edge of the tire.
💡

If you nevertheless decide to install wheels with non-standard ET, be sure to check whether the wheel does not touch the fender liner or suspension elements when the steering wheel is turned completely. To do this, turn the steering wheel all the way left and right on a lift or overpass.

Where to find the right ET for your car

To avoid guessing which offset suits your car, use official sources:

  1. Instructions for use: The "Wheels and Tires" section always lists the acceptable wheel parameters, including ET. For example, for Hyundai Solaris this is ET46–52 depending on the year of manufacture.
  2. Body sticker: On many cars (especially European ones), the wheel parameters are indicated on a sticker in the driver's door opening or on the inside of the gas tank flap.
  3. Official websites of manufacturers:
    • 🔗 Volkswagen — section "Accessories → Discs".
    • 🔗 Toyota — "Selection of spare parts" service.
  • Databases: Services like Diski.ru or AlloyWheelsDirect allow you to select wheels according to the car model, taking into account ET.

    • If you buy used wheels, be sure to check the departure with the database ET catalogs (for example, WillTheyFit.com), where you can check compatibility by VIN or model. Remember: Even if the wheel physically fits on the hub, it does not guarantee that its ET fits your vehicle!

    What should you do if you can't find ET for your model?

    If your vehicle is rare or you are unsure of the data, please contact your authorized dealer to request a technical specification (Wheel Fitment Guide). An alternative is to measure the offset on a standard disc and look for a similar one.

    Consequences of incorrect ET: from visual to critical

    Many car owners mistakenly believe that offset only affects appearance. In fact, the consequences can be much more serious:

    1. Deterioration in handling

    Discs with smaller ET (for example, ET30 instead of ET45) shift the wheel outward, increasing roll-in shoulder — the distance between the point of contact of the tire with the road and the steering axis. This leads to:

    • 🔄 Heavier steering wheel, especially at low speeds.
    • 🚗 Increasing the turning radius.
    • 🌀 At risk aquaplaning due to changes in tire angle.

    2. Accelerated wear of the suspension

    With abnormal ET, the vectors of forces acting on:

    • 🔩 Wheel bearings — the load increases by 20–40%, which reduces their service life by 2–3 times.
    • 🔧 Shock absorbers and springs — uneven weight distribution leads to their distortion.
    • 🛠️ Levers and ball joints - increased wear due to changes in operating angle.

    3. Problems with the brake system

    If the disc is too recessed (large positive ET), it may touch brake caliper. If the offset is negative, the brake force lever increases, which can lead to:

    • 🔥 Overheating of brake pads.
    • ⚠️ False alarms of ABS.
    • 🚨 Lengthening the braking distance by 10–15%.
    ⚠️ Attention: On vehicles with electronic assistance systems (ESP, traction control) abnormal ET can cause errors in the operation of the sensors. For example, on Skoda Octavia With ET other than recommended, the "Check Stability Control" light will often come on.

    The offset of the disc directly depends on its width. The wider the rim, the larger the ET must be so that the wheel does not protrude beyond the arch. For example:

    • 🔹 For disk 6.5J on Kia Rio regular ET - 46 mm.
    • 🔹 For disk 7.5J on the same model, the recommended ET is already 38–40 mm.

    This is due to the fact that as the width of the disk increases, its mating plane automatically moves outward. If you leave the offset the same, the wheel will protrude greatly, which will lead to:

    • 🚗 Touching the fender liners when turning.
    • 💨 Deterioration of aerodynamics (increased air resistance).
    • 🛑 Risk of damage to the disc when driving over uneven surfaces.

    Formula for calculating allowable ET when changing rim width:

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

    Example: if on Ford Focus standard disk 6.5J ET50, and you want to put 7.5J, then:

    New ET = 50 - (7.5 - 6.5)/2 = 50 - 0.5 = 49.5 mm

    Round up to ET50 (nearest standard value).

    💡

    When selecting wide rims, always check whether rolling out the arches will be required. Even if the ET is calculated correctly, the tire width may not fit into the stock space.

    Common mistakes when choosing disks according to ET

    Even experienced car owners sometimes make mistakes that lead to problems. Here are the most common:

    1. Ignoring manufacturer's tolerances: For example, on Nissan Qashqai regular ET - 40 mm, but some install discs with ET30, believing that “10 mm is not critical.” In fact, this leads to accelerated wear of the hubs after 20–30 thousand km.
    2. Buying disks “by appearance”: Discs with negative ET (e.g. ET-20) look aggressive, but without modification of the suspension they are dangerous - the risk increases wheel separation during a sharp maneuver.
    3. Disk width not taken into account: When switching from 6J on 8J Many people forget to adjust the ET, resulting in the wheel protruding beyond the arch.
    4. Trust in "universal" disks: Stores often offer discs with “universal” ET (for example, ET35), but in practice they are not suitable for all cars.

    To avoid mistakes, always check the parameters with manufacturer's catalog or use online matching services such as Wheel-Size.com, where you can virtually “try on” the disc on your model.

    FAQ: Answers to frequently asked questions about ET in disks

    Is it possible to install disks with ET different from the standard one?

    Technically possible, but with reservations: deviation up to ±5 mm usually not critical for most vehicles, but requires regular suspension checks. Deviation more 10 mm not recommended without suspension modification. The exception is sports cars, where negative ET is used to improve handling.

    Which ET is better: positive or negative?

    Optimal for production cars positive ET (for example, ET35–ET50), as it provides a balance between handling and suspension load. Negative ET (ET-10 and below) is used in drifting or rallying, but requires reinforced suspension and wide arches.

    What happens if you install a disk with ET 10 mm smaller than the standard one?

    The wheel will move outward by 10 mm, which will lead to:

    • 🔧 Increase the load on the wheel bearing by ~30%.
    • 🚗 “Weightier” steering wheel and worsening feedback.
    • 🔥 Faster wear of the outer part of the tire.
    • 🛑 Possible wheel hitting the fender liner when turned completely out.

    On vehicles with independent multi-link suspension (for example, Audi A4) this can also cause uneven wear of the silent blocks.

    Where can I watch ET on disc?

    The offset is indicated on the back of the disc in the format ETXX, where XX — value in millimeters. For example, ET45. If the marking is erased, you can measure ET yourself (instructions are given above) or find the parameter in the catalog for the disk model.

    Can incorrect ET be corrected using spacers?

    Spacers allow you to adjust the offset, but this temporary solution. For example, if you need ET40, and the disk has ET30, you can install a spacer 10 mm thick. However this:

    • ⚠️ Increases the load on the hub (the risk of the wheel coming off due to a poor-quality spacer).
    • 🔧 Requires extended bolts or studs.
    • 🚗 May disrupt wheel balance.

    Spacers are only allowed for temporary use (for example when testing wheels) or in sports cars with reinforced suspension.