What Is ET in Rim Size? Wheel Offset Explained Simply

If you have ever seen ET35, ET40, or ET45 written on a wheel and wondered what it means, ET refers to the wheel offset. It tells you how far the wheel’s mounting surface sits from the centre line of the wheel, measured in millimetres.

In simple terms, ET determines how far your wheel sits inward or outward from the car. Choosing the wrong offset can cause tyre rubbing, affect steering and handling, and put additional stress on suspension and wheel components.

For UAE drivers considering new wheels or tyres, checking the correct ET is especially important before making a change.

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What Does ET Mean on a Wheel?

ET stands for Einpresstiefe, a German term meaning “insertion depth.” In wheel terminology, it means offset.

Wheel offset is measured in millimetres and describes the distance between:

• The wheel's centre line
• The mounting surface that attaches the wheel to the vehicle

For example, ET35 means the wheel has a +35 mm offset.

The ET number is important because two wheels can have the same diameter and width but sit very differently on the car if their offsets are different.

Quick Example

If your original wheel is 18x8 ET45 and you replace it with an 18x8 ET25, the second wheel will sit approximately 20 mm further outward, assuming all other dimensions remain the same.

That difference can significantly change clearance and the appearance of your vehicle.

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Where Can You Find the ET Number?

You can usually find the ET marking directly on the wheel.

Check these areas:

1. Behind the wheel spokes
2. Near the wheel hub
3. Around the valve-stem area
4. On the inside of the wheel barrel

You may see markings such as:

• ET35
• ET40
• ET45
• ET50
• ET-10

Some wheels may show the offset without the letters “ET”.

If you cannot find it, check your owner's manual, vehicle specifications, door-jamb information or ask a professional tyre and wheel specialist.

Positive, Zero and Negative ET Explained

Wheel offset is generally divided into three types.

Most modern passenger cars use positive offset wheels.

A lower ET number generally pushes the wheel outward, while a higher ET number generally moves it inward.

What Happens If You Use a Lower ET?

A lower ET moves the wheel outward.

For example, changing from ET45 to ET25 means the wheel moves approximately 20 mm outward, assuming the wheel width stays the same.

This can create:

• A wider-looking stance
• Less clearance between the tyre and outer fender
• More potential for tyre rubbing
• Changes in steering feel
• Additional load on suspension and wheel-bearing components

Lower ET can be useful for certain wheel upgrades, but it should always be checked against your vehicle's approved specifications.

What Happens If You Use a Higher ET?

A higher ET moves the wheel further inward.

For example, changing from ET35 to ET50 moves the wheel approximately 15 mm inward if wheel width remains unchanged.

This may result in:

• More clearance from the outer fender
• Less clearance from suspension components
• Possible contact with struts or brake components
• A more tucked-in appearance

So, a higher ET isn't automatically better. The correct value depends on your vehicle, wheel width, brake setup, and tyre size.

Why Does Wheel Offset Matter?

1. Tyre and Fender Clearance

Incorrect ET can cause your tyres to rub against the inner suspension components or outer fender.

This is particularly important if your vehicle has been lowered or fitted with wider tyres.

2. Steering and Handling

Changing wheel offset changes the wheel's position relative to the steering axis. A significant change can affect steering feel, stability, and the way the car responds to bumps.

3. Suspension and Wheel Bearings

A major offset change can alter the loads placed on wheel bearings and suspension components.

That's why simply choosing a wheel because it “looks good” isn't enough.

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4. Brake Clearance

The correct offset also helps ensure the wheel clears your brake calipers. This becomes particularly important when installing larger aftermarket brakes.

5. Vehicle Appearance

ET has a major effect on stance.

• Higher ET: wheels sit more inward
• Lower ET: wheels sit further outward
• Negative ET: wheels can create an aggressive, deep-dish appearance

How Do You Calculate Wheel Offset?

If the ET isn't marked on your wheel, you can calculate it by measuring the wheel.

You generally need:

1. The wheel's total width
2. The wheel's backspacing
3. The wheel's centre line

The basic relationship is:

Offset = Backspacing − Centre Line

For example, if a wheel's centre line is 100 mm and the backspacing is 120 mm:

120 − 100 = +20 mm

So the wheel has approximately ET20.

For an accurate measurement, the tyre normally needs to be removed because the wheel's bead-seat dimensions are what matter.

Common ET Values

There isn't one universal ET value that fits every car. However, you'll commonly see values such as:

These are only general ranges. Always verify the manufacturer's recommended fitment for your specific vehicle.

Does ET Affect Tyre Wear?

Yes, changing ET significantly can influence tyre wear.

An incorrect offset can alter the wheel's relationship with the suspension and steering geometry. If the setup is significantly outside the vehicle's intended specifications, it may contribute to uneven tyre wear or changes in handling.

If you notice unusual wear after installing different wheels, have the wheel alignment and fitment checked.

Is ET Important When Buying New Wheels in the UAE?

Absolutely.

Before buying aftermarket wheels in the UAE, check:

• Wheel diameter
• Wheel width
• ET/offset
• PCD/bolt pattern
• Centre bore
• Brake clearance
• Tyre size
• Load rating
• Vehicle manufacturer specifications

You should also make sure the final setup doesn't cause excessive tyre protrusion or clearance problems and complies with applicable UAE vehicle requirements.

For UAE roads, it's especially important to choose a properly matched wheel and tyre combination rather than selecting an offset based only on appearance.

FAQ

What does ET mean on wheels?

ET means wheel offset. It describes the distance, in millimetres, between the wheel's centre line and its mounting surface.

Is ET35 better than ET45?

Neither is automatically better. ET35 places the wheel further outward than ET45 when the wheel width is otherwise identical. The correct ET depends on your vehicle's specifications and wheel dimensions.

Does a lower ET push the wheel out?

Yes. A lower positive ET generally moves the wheel outward, while a higher ET moves it inward.

Does ET affect tyre rubbing?

Yes. Changing ET changes the wheel's position and can affect clearance between the tyre, fender, suspension, and brake components.

Can wheel spacers change ET?

Yes. A spacer effectively moves the wheel outward, reducing the effective offset. However, spacers should be selected and installed correctly because they can affect wheel-bearing loads, clearance, and vehicle compliance.

Where can I find my wheel's ET?

Look for markings such as ET35 or ET45 on the back of the spokes, wheel hub or inside barrel. If there is no marking, check the vehicle documentation or consult a wheel specialist.