Can rims with a larger ET be fitted?

2026-03-25

For many drivers, changing rims is the first step toward improving the appearance of their car or tailoring it to their needs. We often focus on the design, diameter in inches, or color. However, choosing rims is primarily a matter of technical parameters, which directly impact handling and driving safety. One of the key markings is the rim's offset, or wheel ET. This determines how far the wheel will extend into the wheel arch or how far it will protrude outward. Even a small change in this parameter can affect suspension geometry, bearing load, or the risk of rim contact with braking components.

Is it possible to install rims with a larger ET than recommended by the manufacturer? In many cases, yes – but only if all rim parameters are carefully analyzed and the vehicle's potential design limitations are taken into account. In this article, we'll explain when such a change is safe and when it could lead to technical problems.

What is rim ET and why does it matter?

Before we answer the question of whether it's possible to install rims with a larger ET, we need to precisely explain what this parameter actually is. In practice, it's one of the most important dimensions, affecting not only the car's appearance but, above all, its construction and driving safety. Without understanding what a rim's ET is, it's difficult to consciously assess the risk of changing it.

Definition of ET – the foundation of circle geometry

Rim offset (from the German Einpresstiefe) is the distance between the rim's mounting surface (where it meets the hub) and the geometric center of its width. This value is given in millimeters and can be positive, zero, or negative.

In practice, this means that:

the higher the ET, the more the rim "goes" into the wheel arch,
the smaller the ET, the more the wheel moves outwards,
Changing the ET without changing the rim width causes the entire wheel to shift relative to the hub.

It's the offset of the rim that determines how the wheel sits in the wheel arch—whether it's tucked in or protrudes closer to the fender edge. In a context like car wheel design, offset isn't an aesthetic detail, but a design parameter that influences the distribution of forces acting on the suspension.

Why is ET crucial to car design?

The ET parameter has a direct impact on several key design elements of the vehicle.

First, it changes the effective wheelbase. Even a difference of just a few millimeters can affect driving stability and the way the car responds to steering inputs.

Secondly, it affects suspension geometry. Car manufacturers design their steering and suspension systems with a specific ET in mind. Changing this value can affect:

scrub radius,
wheel bearing load,
the work of the rockers and pins,
wear of suspension components.

Thirdly, it affects the physical fit of the rims to the specific car model. Too high an ET can cause the rim or tire to contact the shock absorber or brake caliper. Too low a ET can result in rubbing against the fender.

It's worth emphasizing that car manufacturers calculate the ET for each model very precisely, taking into account the vehicle's weight, suspension characteristics, and homologation requirements. Therefore, changing this parameter should always be a conscious decision, not a random choice based solely on the availability of a given wheel model.

Can rims with a larger ET be fitted?

This is the key question of this article. The answer is yes, in many cases it is possible, but only with a thorough analysis of the wheel arch space and consideration of the suspension and braking system design. Changing the wheel offset isn't just a matter of aesthetics—it also affects the wheel's geometry. Therefore, before opting for a rim offset larger than the manufacturer's specifications, it's worth understanding what the actual changes are to the car.

What happens when we increase ET?

The principle is simple: the larger the rim's offset, the more the wheel moves inward toward the wheel arch. This means that, for the same rim width, changing the offset causes the entire wheel-tire assembly to move toward the suspension.

If the manufacturer specifies an ET of 40, and you install a rim with an ET of 50, the wheel will "move back" 10 mm towards the suspension strut. In practice:

visually the wheels become more "hidden",
the car may look less dynamic (wheels falling into the wheel arch),
the distance between the tire and the suspension elements is reduced.

That's why the question "can I fit rims with a larger offset?" shouldn't be considered solely in terms of appearance. Changing the offset has design implications that aren't immediately apparent.

Potential technical problems with too high ET

The greatest risk with too high an ET comes from the limited space on the inside of the wheel. Consequences of a larger ET can include:

1. Rubbing against suspension components

The wheel can come close to the McPherson strut, shock absorber, spring, or control arm. Even if everything appears correct during static adjustment, contact can occur during driving due to suspension deflection. Tire rubbing is a real risk, leading to damage and a decrease in driving safety.

2. Collision with the brake caliper

In modern cars, especially those with larger discs and extended calipers, mounting space is very limited. Too large an ET can prevent the rim from providing adequate clearance for the brake caliper. In extreme cases, mounting is physically impossible.

3. Impact on turning radius and stability

Changing the wheel's position relative to the steering knuckle affects the scrub radius. While a difference of a few millimeters doesn't always result in drastic changes, larger deviations can result in:

a different reaction of the car to the steering wheel turn,
increased sensitivity to ruts,
changed feeling of stability at higher speeds.

Therefore, answering the question "can rims with a larger ET be installed?" should always be preceded by a technical analysis of the specific vehicle model. In some cases, a difference of 5 mm will be safe, while in others, a difference of 8–10 mm can mean a real risk of collision with the vehicle's structural components.

Larger rim ET vs. rim width

When considering changes in ET, this parameter cannot be analyzed in isolation from rim width. In practice, rim width and ET are two closely related elements that together determine the exact position of the wheel relative to the hub, suspension, and fender. Many drivers focus solely on ET, overlooking the fact that even with identical offset, a wider rim changes the position of both the inner and outer edges of the wheel.

Relationship between width and offset

ET alone isn't everything. As we increase the width of the rim, its geometric center also shifts. This means that:

a wider rim with the same ET will stick out more,
at the same time, it will be closer to the suspension elements from the inside,
changing ET and width simultaneously may partially compensate – or worsen the problem.

Practical example:

Change from 7J ET40 to 8J ET45 .

The difference in width is 1 inch, or 25.4 mm. Half of this value (12.7 mm) extends to each side of the rim's centerline. At the same time, the ET increases by 5 mm.

As a result:

the inner edge of the rim will come closer to the suspension by approximately 17–18 mm,
the outer edge will protrude slightly less than in the case of just increasing the width (because part of the difference is compensated by the larger ET).

This demonstrates that aluminum rim parameters such as width (J) and ET must be considered together. This is why it's important to perform precise calculations before making any changes, rather than relying solely on intuition.

Why use an ET calculator before purchasing?

Click on the image to go to the calculator

For more complex modifications (different width + different ET + different tire diameter), manual calculations can lead to errors. Therefore, one of the essential tools for modifications is an ET calculator .

A good ET calculator allows you to:

compare the old and new rims,
check how many millimeters the wheel will come closer to the suspension,
determine how much the outer position will change relative to the fender,
assess whether a safe installation space will be maintained.

When analyzing the results, pay particular attention to the offset value on the inner side. This number represents the potential risk of friction with the shock absorber, McPherson strut, or braking system components.

Professional wheel ET calculation is now standard for informed wheel selection. If you're wondering how to choose wheels, an ET calculator should be your first step before placing your order – especially if you plan to change more than 3–5 mm from the manufacturer's specifications.

How to safely choose rims with a larger ET?

The decision to install rims with a larger ET shouldn't be left to chance. Even if the difference seems small, maintaining an appropriate safety margin is crucial. The rim ET – the selection must take into account both the vehicle manufacturer's specifications and the actual amount of space in the wheel arch. Below are practical rules that can help reduce this risk.

Permissible error limits (tolerance)

In practice, it is assumed that the permissible ET of the rim can differ from the factory one by about 5-10 mm - provided that the rim width is not significantly changed and that the car design provides adequate space.

A commonly used rule of thumb is to maintain a change in track width of approximately ±1%. In most passenger cars, this translates to a difference in ET of just a few millimeters. This is the range within which:

the suspension geometry is not significantly disturbed,
we do not increase the load on the bearings excessively,
we do not significantly impair the stability of the driving track.

The problem begins with larger wheel travels, such as a change from ET35 to ET55. This 20 mm difference translates into a significant wheel offset towards the suspension and often results in a lack of space for safe installation. In such cases, the ET tolerance is significantly exceeded, and the risk of collision with the car's structural components is high.

Therefore, any change above 8–10 mm should be treated as potentially problematic and requiring careful analysis.

Measurements "from nature" - how to check the amount of space?

Before you decide to buy rims with a larger ET, it is worth taking a simple but very effective step: check the real amount of space in the wheel arch.

How to check rim ET in practice?

1. Measure the distance from the inside edge of the tire to the shock absorber or McPherson strut.

It's best to use calipers or a precision steel gauge. The minimum safe margin should be a few millimeters – remember that the suspension moves while driving.

2. Check the space with the wheels turned.

At maximum steering angle, the wheel changes its position relative to the wheel arch and suspension components. This is the point where rubbing most often occurs.

3. Take suspension sag into account.

A stationary vehicle experiences different conditions than a moving vehicle with passengers and luggage. Wheel installation must take dynamic loads into account.

If your measurements indicate, for example, that you have 15 mm of free space on the suspension side, and the planned ET change will cause the wheel to move 12 mm inward, the safety margin will be minimal. In such a situation, the decision should be made very carefully.

A professional offset measurement and wheel arch analysis are the surest way to avoid costly purchase mistakes. Without this, even a theoretically "safe" modification can prove problematic in practice.

When does an ET change require correction?

Sometimes, selected rims have an ET that's too high for the vehicle's specifications, but are otherwise perfectly matched in terms of design, diameter, and width. In such a situation, the question arises: can the ET be adjusted to ensure safe installation? In many cases, yes, but this requires the use of appropriate technical solutions and adherence to rigorous installation guidelines.

Wheel spacers – a way to save rims with too high ET

The most common correction method is the use of wheel spacers. A spacer is a metal ring mounted between the hub and the rim, physically moving the wheel outward. In practice, this reduces the effective wheel offset.

The principle of operation is simple:

ET50 + 15 mm distance = effective ET35

This means that the spacer "reduces" the offset by its own thickness. This allows you to fit rims with a larger offset to a car that requires a smaller offset.

There are two basic types of wheel spacers:

1. Travel distances

Installed with longer screws. Typically used for thinner thicknesses (e.g., 3–15 mm).

2. Screw-on spacers (with their own pins/screws)

First, they are bolted to the hub, and then the rim is attached to the spacer. Used for larger wheel thicknesses (usually over 15–20 mm).

Wheel spacers are an effective way to correct ET, but they shouldn't be considered a forced solution. Their selection must be precise and tailored to the specific car.

Safety of assembly using spacers

Simply changing the wheel offset using a spacer isn't dangerous – provided the installation is done correctly. The key elements are:

1. Suitable wheel bolts

For thru-axle spacers, longer bolts are necessary to maintain the correct thread length in the hub. A bolt that's too short poses a real risk of loosening the wheel.

2. Hub centering

The spacer should be hub-centric – meaning it should have the correct centering hole and centering lip for the rim. Improper centering can cause vibrations at higher speeds.

3. Tightening torque and post-assembly inspection

After mounting wheels with spacers, it is recommended to check the tightening torque after driving several dozen kilometers.

4. Legal issues and technical inspection

In Poland, wheel spacers are permitted as long as the wheels don't protrude beyond the bodywork and don't interfere with the vehicle's structure. During a technical inspection, the diagnostician assesses whether the modifications will negatively impact safety. For larger changes, it's worth ensuring that homologation requirements are met.

In summary, changing the wheel offset by using wheel spacers is possible and often done, but it requires a conscious approach. This is a component of the chassis, so safe wheel installation should be an absolute priority.

Frequently Asked Questions (FAQ) – Rims with a larger ET

Can I install rims with a larger ET than the factory ones?

Yes, it's often possible, but a larger ET moves the wheel further back in the wheel arch . In practice, this means a greater risk of contact with the inner components: the shock absorber/strut, spring, control arm, covers , and sometimes the brake caliper (depending on the rim design, not just the ET).

Changing a few millimeters can be hassle-free, but safety depends on the entire setup: rim width, tire size and actual width, profile, suspension geometry , and how much clearance you have from the factory. If the wheel is set back too far, the problem usually occurs not in a straight line, but rather when cornering, under suspension flex , and under load.

How much can the ET of a rim be increased without the risk of rubbing?

There's no single universal value for all cars. Many cars can tolerate a 2-5mm change in ET, but there are models where just +3mm can eliminate critical play at the strut or control arm, especially with wider rims and tires.

The best rule of thumb is simple: increasing ET by X mm reduces internal play by X mm (and simultaneously tucks the wheel further into the wheel arch by X mm). If you want to increase ET, check the actual free distance on the inside and leave a safe margin: a minimum of about 3–5 mm of play at the closest point, and for cars with soft suspension or significant deflection, more is better.

What happens if ET is too high?

Too much ET can cause:

rubbing from the inside (McPherson strut, spring, wishbone, covers),
problem with assembly (no space for clamp or suspension elements),
sometimes the steering system works worse (different sensations on the steering wheel),
greater susceptibility to rubbing at full turn or on uneven surfaces.

Regarding the bearings: simply moving the wheel more inward is usually not as "loading" as pushing the wheel outward a large distance, but you are still changing the suspension operating conditions and geometry (including the caster radius ), so extreme deviations from the factory are not a good idea.

Does a larger ET reduce the wheelbase and affect handling?

Yes. A larger ET "tucks" the wheel inward, so the track width decreases (on an axle in total by about 2 × the ET difference , if the width and other parameters remain the same).

The impact on handling depends on the scale of the change and the car, but typically:

the car may be slightly less stable compared to a wider track,
the suspension geometry changes (including the swing radius),
the feeling of forces on the steering wheel and the reaction to ruts may change.

This does not mean that every change of 3–5 mm will be immediately “bad” – but with larger deviations the differences can be clear.

Do spacers completely solve the problem of too high ET?

The spacer can "correct" an excessively high ET by reducing the effective ET (e.g., ET45 + 5 mm spacer ≈ ET40). This often works, but it's not always an ideal solution because:

the spacer pushes the wheel outwards – so there may be friction against the wheel arch from the outside,
a greater wheel extension usually increases the load on the running gear components more than moving the wheel back inwards,
you need to select the correct type (through/screwed) and the appropriate screws with the correct length and cone/ball.

Spacers are commonly used in everyday use, but they must be selected and installed correctly: centering, clean seating, proper torque, and inspection after driving several dozen kilometers . For thicker spacers, bolt-on spacers are more often chosen.

How can I check if a rim with a larger ET will fit my car?

The ET calculator is a good starting point, but it does not replace measurement , as it does not take into account all design differences (e.g. the shape of the rim spokes, the actual tire width, clearances in a specific car).

The surest method:

Measure the current internal clearance (to the strut/wishbone) and external clearance (to the wheel arch lips) on the current set.
Calculate the offset resulting from the change in ET and rim width (if it changes).
Leave some margin for tire and suspension work: 3-5 mm is generally considered the absolute minimum at the closest point, and more is safer.
If possible: try on one rim for the front and rear (important: full steering angle, suspension deflection, load).

If you are changing rim width or tire size at the same time, checking "ET only" may give you a false sense of security.

Can changing the ET be a problem during the MOT?

It may, if it results in a condition that the diagnostician deems unsafe or inconsistent with the vehicle's roadworthiness requirements. The most common "trouble spots" are:

rubbing against suspension or body parts,
tire protrusion beyond the outline of the fender/wheel arch,
incorrect selection of tires/rims (e.g. lack of required load capacity, damage, incorrect mounting),
looseness and damage to running elements that will be revealed during inspection.

The mere fact that the ET differs from the factory one by a few mm is not "automatically" a basis for a negative result - the key is whether the wheels are mounted correctly, nothing rubs, and the vehicle meets the road safety requirements.

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