What is ET disk flyout and what affects

Marking alloy wheels often makes car owners think: “Will these wheels suit me, will they touch levers, arches or brake calipers?”. One of these parameters is the departure of the disk, what it is and how to recognize it, we will try to tell you in this material in simple words.

Departure disk - this is the distance between the plane of the disk that is in contact with the hub of the car and the axis that bisects the disk.

The parameter of the disk departure is indicated by two letters ET (Einpress Tief, which means indentation depth) and measured in millimeters.

It will be clearer to show in the figure:

What is the offset of the rim

As you already understood from the image above, the crash happens:

• positive;
• negative;
• null.

A positive overhang means that the plane of the disc-to-hub attachment is behind the center plane of the disc, closer to the outside of the disc.

With a negative overhang, similarly, the hub mounting plane is behind the center plane of the disc, but closer to the inner side of the disc.

It is logical that at zero overhang, these two planes coincide.

How to find out the disk departure

At first: on alloy wheels, on the inside, there should always be a marking of its parameters, below in the photo we have highlighted the place where the parameters are indicated.

Judging by the photo, we conclude that the ET35 offset is positive.

Secondly: disk overhang can be calculated, but this is a more methodical method that few people use, but it will be useful to understand what a disk overhang is.

You can calculate the departure using the formula: ET \u2d S - B / XNUMX

• S is the distance between the plane of attachment of the disc to the hub and the innermost plane of the disc;
• B is the width of the rim;
• ET - disk crash.

What affects the disk departure

First of all, the disc overhang affects how the disc will be positioned in the arch.

The larger the overhang, the deeper the disc will be located in the arch. The smaller the overhang, the wider the disc will protrude relative to the hub.

Impact on the chassis

In order not to go deep into physics, it is better to show in the picture what forces act on the suspension elements (levers, wheel bearings, shock absorbers) of the car.

So, if, for example, we reduce the overhang, that is, make the car's track wider, then we thereby increase the shoulder of the impact of the load on the suspension elements.

What this can lead to:

• shortened service life of elements (faster wear of bearings, silent blocks of levers and shock absorbers);
• breakage during a one-time significant load (falling into a deep hole).

Example: what is the difference between departures 45 and 50

Based on the above definition, an ET50 offset disc will sit deeper in the arch than an ET45 offset disc. What does it look like on a car? See the photo:

Remember that each car has its own factory offset readings. That is, wheels with an offset of ET45 on one car will also not “sit” on a car of another brand.

Disc offset 35 and 45

As mentioned earlier, the ET (Effective Displacement) rating can determine whether the selected wheels will fit the vehicle. ET is calculated using the following formula: ET = A – B, where:

• A – distance from the inner surface of the wheel rim to the area of ​​its contact with the hub (in millimeters);
• B – disk width (also in millimeters).

The result of this calculation can be of three types: positive, zero and negative.

1. A positive result means that there will be a small gap between the area where the wheel touches the hub and the hub itself. In this case, the wheels are ideal for this car.
2. A zero result indicates that the discs can theoretically be installed on the car, but there will be no clearance between them and the hubs, which will increase the load from impacts when driving through holes or bumps.
3. A negative result means that the rims will not fit the car, as the hubs will not allow them to fit under the wheel arch.

Effective offset (ET) plays an important role when choosing wheels for a car, and its correct selection will help avoid problems with the suspension and handling of the car.

Tolerances

We have already figured out what the ET (effective bias) indicator is and how to calculate it. Now let's preview the valid options for this indicator before moving on to the difference between the values ​​of ET 40 and ET 45. The valid ET values ​​can be found in the table below:

Based on this table, we can conclude that the offset size of the rims affects whether they are suitable for your car. If you ignore this parameter, you may waste your money.

Now, having learned what the permissible disc offset is and how to calculate it, let's move on to the question that interests many car enthusiasts: what is the difference between the values ​​of ET 40 and ET 45? The answer to this question is:

1. Firstly, when installing discs with a lower ET value, the load on the wheel bearings will increase slightly. This may reduce the life of these parts and cause increased wear.
2. However, if you compare the values ​​of ET 40 and ET 45, you will notice almost no difference. It becomes noticeable, for example, when comparing discs with ET 20 and ET 50, where reduced wear resistance will begin to appear after just a few months. In addition, the stiffness of the suspension will increase due to the lack of play between the wheel and the hub.
3. Secondly, the difference will be in visual perception. For example, when installing wheels with ET 40, the wheels will hardly protrude beyond the car's arches, while ET 45 will force them to move outward by 5 mm, which will be visible visually.

It is important to note that this change can be either positive or negative. Some car enthusiasts specifically choose wheels with a long offset to make the car's wheelbase visually wider. Overall, there will be virtually no difference between the values ​​of ET 40 and ET 45, and you can safely install both options on your car without worrying about any serious consequences.

Departures table by car brand

Earlier, we have already published material, in the tables of which you will find the factory departure for each car brand: wheel bolt table... Follow the link and choose the desired car brand.

What if the disc offset does not fit the vehicle

If the disc offset is greater than the factory offset of the car, then disc spacers can help in this case. Follow the link for a separate article that will tell you in detail about the types of spacers and how to use them.

Video: what is disk crash and what does it affect

What is drive bust or ET? What does it affect? What should be the offset of disks or ET?

Questions and answers:

How is disc overhang measured? Et is measured in millimeters. There is zero (the middle of the longitudinal section coincides with the plane of attachment with the hub), positive and negative overhang.

What happens if you increase the disk offset? The track of the car will decrease, the wheels can rub against the arches or even cling to the brake calipers. To make the wheels wider, the overhang must be reduced.

How does disk flyout affect? The smaller the overhang, the wider the wheels will stand. The steering behavior, the load on the wheel bearings and other elements of the chassis and suspension will change.