What is disk offset ET in simple words (parameters, influence and calculation)

• Introduction
• What is disc ejection?
• What kind of departures are there?
  1. Zero departure

  Positive departure

• Negative departure
• ET number
• Can I change the offset without changing the disk?
• How does an incorrect offset affect a car?
• Why change the disc offset?
• How to measure disc offset? Recommendations
• conclusions

Disc ejection: what is it?

Disc offset, or ET indicator, is a dimensional parameter that is indicated on the rim of the product, regardless of its radius or material of manufacture (stamped, cast or forged), and indicates the distance from the mating plane of the wheel to the attachment point to the hub.
This dimension is usually set by the car manufacturer. First of all, the wheel must be completely hidden under the wheel arch, and it is the ET indicator that regulates its position - the larger it is, the more the wheel is recessed under the wing; the smaller, the more noticeably the disk protrudes beyond the dimensions of the body.

ET offset on wheels: what is it and how does it affect the suspension and other parts in the car? Depending on the wheel offset, the load on the hub and the bending moment applied relative to it at the base of the suspension are distributed differently. Thus, each automobile concern dictates the strength limit for its parts, which determines the range of wheel offsets.

Some cars, especially when it comes to SUVs and sports cars, are equipped with additional plastic mud flaps, which determine the wheel offset, which in such cases can be zero or even negative, which gives the “iron horse” a very impressive look.

ET departure using 3 indicators as an exampleImportant! Before purchasing a wheel rim, the driver needs to read the owner's manual for his car or study detailed information on numerous Internet resources in order to make the right choice and not regret it later.

Types and mechanical characteristics

There are 3 types of wheel offset:

• null;
• positive;
• negative.

The offset coding (ET) is located on the surface of the rim, and the numbers located next to it indicate its parameters.

A positive offset value means that the vertical axis of the wheel rim is at a certain distance from the point of contact with the hub.

The zero ET parameter indicates that the disk axis and its mating plane are identical.

With a negative ET parameter, the disk attachment surface to the hub moves beyond the vertical axis of the disk.

The most common disc offset is a offset with a positive value; a negative offset, on the contrary, is extremely rare.

The offset size is a significant nuance when designing wheel rims, so a special formula is used to calculate it to eliminate possible errors.

How is ET disc offset measured?

The parameter is measured only in millimeters. You will need a ruler and a wooden (or metal) strip, the length of which coincides with the radius of the wheel.

1. First of all, you need to remove the wheel from the car and put the car on the handbrake. If the wheels have alloy wheels, the procedure will be greatly simplified, since all the nuts on them are open. Otherwise you will have to remove the cap.
2. Now you can remove the disc from the wheel. This must be done with a sharp movement.
3. The wheel should be placed on the ground with the side opposite the hub. We place a wooden strip on top of the disc rim.
4. Then, using a ruler, measure the distance from the surface in contact with the hub to the bottom of the rack - this will be distance A.
5. Next, we turn the other side of the wheel towards the ground, and also place the rack on the rim.
6. We measure the distance from the bottom of the rack to the plane beyond which the hub is distance B.

Formula and labeling

The term disc overhang is designated by the letters ET from the German Einpress Tief (extrusion depth). Its calculation formula is as follows:

ET=ab/2

where a is the distance between the inner plane of the disk and the part that comes into contact with the hub, b is the width of the disk. You can see it most clearly in the figure below.

The calculation is made in millimeters. In some cases, instead of the letters ET, the disc offset is marked with the following inscriptions: DEPORT or OFFSET. For example, the following values ​​may be: ET0, ET30, ET-15.

Varieties of departure

There are three types of offset, each of which is assigned a corresponding marking (painted on the inside of the disk):

• ET20 (zero offset) - when the surface with which the disc is pressed against the hub coincides with the central plane of the wheel,
• ET0 (positive offset) – the vertically located axis of the disk is distant from the point of contact with the hub by a certain distance,
• ET-20 (negative offset) - when the surface with which the disc is attached to the hub is carried beyond its vertical axis.

Today the most common disc offset is ET0. Negative and zero offsets, on the contrary, are rare. Wheels with such an offset are installed on specially prepared cars, for example, for racing, both off-road and on tracks.

The offset parameters are regulated by vehicle manufacturers, and, as they say, there should not be any deviations (even a few mm). Otherwise, the operating conditions of all suspension units change, which under critical load conditions can lead to tragedy.

ET on disks - what does it mean and how is it calculated

The designation in the form of two letters of the Latin alphabet ET is not accidental, since this value is international and is determined by the following formula and is expressed in mm, regardless of the country of the disk manufacturer:

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ET = X – Y/2,

Where X is the distance from the outer mating plane of the disk to its inner edge on the side of attachment to the hub or the size that is determined by measuring from the side edge of the wheel along the sides to its grille.

Y is the overall width of the product along the rim.

Important!

As a marking, wheel manufacturers, as a rule, prescribe this value as ET20, ET35, ET42, etc., and any professional can always read it and define these values.

Disc with negative offset

What does disc ejection affect?

The following quantities are associated with departure:

1. Wheelbase.
2. Torque applied to a wheel bearing.

Both parameters need to be considered in detail.
Depends on the wheelbase:

1. Sustainability. Improves with increasing distance between wheels. For this reason, SUVs have zero or negative offset.
2. Controllability. It is the best for the wheelbase that the designers laid down.

The moment acting on the wheel bearing is calculated as the product of 2 quantities:

1. The force with which the road acts on the wheel.
2. Arm - the distance from the direction of action of the force to the point relative to which it causes rotation.

The road affects the wheel along the entire contact patch, and the total force vector passes through its midpoint. If the tires are not worn out and the wheel alignment is adjusted, this point lies in the central plane of the disk.

Thus, the further the vertical axis of the wheel is from the bearing, the greater the moment acting on it.

Are different parts needed for different configurations of the same car model?

A huge number of people work on the creation of one car - from designers to interior assemblers. Of course, special attention is paid to the chassis. During its development, hundreds of parameters are taken into account, each of which will determine the requirements for the design of individual elements.

Today, there are many car brands and even more models on the automobile market. The situation has become quite common when a manufacturer launches models on the market that differ only in engine size. It would seem that the components for them should also be the same, but this is not the case. Many details may differ, including:

• Levers;
• Ball joints;
• Silent blocks;
• NRT, etc.

Such decisions are very natural. The slightest difference in the mass or overall dimensions of the engine affects the distribution of forces that affect the chassis and suspension, in particular. Based on this, to ensure the necessary maneuverability and comfortable ride, it is necessary to use other components. The way out of such situations previously was to create a good safety margin for the driving components of the car. Now this approach is becoming a thing of the past, giving way to precise calculations, which results in a significant reduction in the cost of developing and manufacturing vehicles.

Why install wheels with a different offset?

Installing wheels with a reduced offset helps to increase stability and, as a result, the wheelbase of the car. Thus, the car is able to turn confidently and has high road stability. Some changes to the suspension improve overall ride comfort, but it also changes the operation of springs, levers, brakes, bearing wear, hub wear and other handling parameters.

Sometimes installing wheels with a smaller, relatively standard offset allows you to reduce the weight of the suspension and thereby improve dynamics and fuel consumption in certain modes.

As the offset increases, the track decreases, and if you do this without preliminary calculations, the wheel may simply rest against the brake caliper or touch the inside of the wheel arch.

The increased reach also affects the operation of the suspension units and the chassis of the vehicle. As a rule, wheels of smaller size and diameter are installed on some versions of cars during winter operation, but the effectiveness of this phenomenon has not been proven, and smaller versions are practically not used in the tuning process.

If we talk about which wheels to choose, then in this case it all depends on the car model, tuning capabilities and other factors. There are disks that are made by hot stamping, others - under high pressure and metal processing.

Forged ones are stronger and lighter, but this does not mean that they are suitable for all car models, it all depends on the situation. When choosing a disk, it is necessary to take into account the meanings and interpretation of the markings in accordance with international standards, where:

• ET – Disc Overhang may be designated as Offset Internal or Extending
• B is a measure of the width of the rim between the edges of the rims (measured in inches. 1 inch = 2.34 centimeters
• “J” is a special service symbol that indicates the design features of a particular model
• “D” – diameter of the mounting rail, “d” – diameter of the hole for the wheel hub

It should be added that there are cases when wheels with an increased or decreased offset fit on a standard wheel hub without problems. However, this does not mean that their use will be safe for various suspension elements.

Automaker engineers carefully calculate all aspects of the behavior of the wheel, hubs, shock absorbers, steering ends, levers, etc., so using discs with sizes not recommended by the manufacturer can significantly reduce the overall life of all these parts.

What kind of departures are there?

Zero departure

Zero or neutral offset is obtained when the mounting plane of the disk exactly coincides with its center line. Discs with zero offset are designated ET0.

Positive offset A disc has positive offset when the plane in contact with the hub is in front of its centerline. When viewed directly from the front, discs with positive offsets appear flat or, less commonly, concave. Positive offset is seen on some older cars' rims, where the wheel hub protrudes further than the rest of the wheel. Too much offset can put pressure on the hub and axle and even break these parts.

Negative offset The mounting surface of negative offset discs is located behind the center line of the wheel. In this case, what is visually striking is that the seat is deeply recessed into the disk, and the disk itself seems, on the contrary, to protrude outward. Such discs often have aggressive shapes with many concave elements.

Take into account the disc offset features when buying a new set. Most people buy discs based on their appearance and design, without delving into the ET parameter. And it is very important during installation. Consult with a specialist before purchasing a set of wheels that are more or less offset than the stock ones for your vehicle.

ET number

The letters ET stand for einpresstiefe 一 insertion depth. The ET parameter denotes the amount of overhang - the distance from the mounting plane to the center line in millimeters. This indicator is stamped on the rear spokes or mounting surface of the alloy wheel and is indicated in the markings. For example, let's take a disk labeled 7.5×18/5×105 D56.6 ET42. Disc offset size, ET, 一 42 mm. From the designation ET42 we can understand that we are dealing with a positive offset. This means that the mating plane protrudes 42 mm relative to the center line of the wheel. If this model had a negative offset, then instead of ET42 we would see ET-42 - the mating surface is 42 mm behind the center line of the disk. In the case of zero offset, the marking would be ET0, which would mean that the center line and the mounting surface of this disk coincide. It is important to consider the ET parameter if you want to install rims on the car that are physically wider than the ones that came before. In this case, the offset may need to be adjusted to compensate for the larger width. Such manipulations are quite risky; it is recommended to carry them out under the guidance of experienced professionals, or it is better to select discs that exactly match the parameters.

Can I change the offset without changing the disk?

The offset can be changed, but there are certain risks for the car, which we discuss below. Manufacturers now offer spacers in different sizes to adjust the standard offset of your vehicle. Spacers significantly reduce the distance from the center of the disk to the hub, thereby reducing the positive offset to the negative side. Chances are that if you add spacers, the standard bolts won't go all the way in and the rims won't fit properly. You can take long bolts to accommodate the spacer, or change the bolt design to a stud design using a stud conversion kit. In any case, greatly changing the offset, either positively or negatively, should be done with extreme caution. We recommend that you evaluate all the risks before installing rims with a larger or smaller offset than recommended. In the configurator of the “Selection by car” section, you can see both the recommended offsets and the permissible deviations from them - in tuning sizes suitable for your car model. The selection is based on parameters that allow you to safely install rims on a car.

The managers of our online store do not recommend purchasing car wheels with an offset that does not correspond to the specified recommended or tuning sizes. Of course, if the client himself insists on purchasing, they will sell him the wheels, but first they will explain the risks of installing such models for the car.

How does an incorrect offset affect a car?

One of the main reasons why you should not change the offset to too positive or negative relative to the recommended one: this manipulation will automatically remove the car from warranty. It’s worth considering how much you need such tuning. If you greatly reduce the disc offset relative to the standard one, the wheel will either stand flush with the arch or begin to protrude from it. In the best case, your car with such discs will get dirty faster: with a reduced offset, much more dirt will fly onto the doors and side windows than with normal ones. In the worst case scenario, the tire will begin to rub against the wing, and the operation of the steering wheel will be disrupted. All this can lead to poor handling. It is dangerous to drive with such a defect. An increased offset will sink the wheel more into the arch. In this case, there is a risk that the disc will start to touch the caliper, and the tire will start to touch the wheel arch liners and suspension parts. Excessive positive overhang can cause damage to the inner suspension and brake components at the inner edge. The result is poor handling and instability of the car at speed. It is also unsafe to drive out onto the road. Conclusions: a strong deviation of the departure parameters in a positive or negative direction can change the operating conditions of all suspension components, creating forces (and vectors of their application) for which the suspension is not designed. The most “favorable” outcome of installing a disk with an inappropriate offset is a reduction in the service life of the suspension elements. Under critical load conditions, the consequences can be much more serious, including accelerated wear of the chassis and sudden destruction of suspension parts while driving. In addition, by changing the offset too much, you risk the car manufacturer's warranty.

Why change the disc offset?

Many car enthusiasts strive to give their car a more presentable, aggressive or sporty look. To do this, they resort to various methods, including creating a “wider position” for the car by reducing the reach. This is one of the most popular reasons why such tuning is done. Indeed, a 10mm deviation in ET can significantly change the appearance of the car. If you decide to install wheels with a smaller or larger offset relative to the standard one, pay attention to the tuning dimensions that we indicated in the configurator of the “Selection by car” section for each model. However, there is still a small risk that such wheels, even with acceptable offset deviations, may not fit the car. We have minimized the risk of such a situation occurring, because... To calculate tuning dimensions, regulated and measurable parameters were used. But it is beyond our power to take into account the correspondence of the internal area of ​​the disk, the protruding parts of the suspension and the brake mechanisms of the car. Taking into account these nuances, as well as the remote nature of the purchase, we recommend trying on the wheel before tire fitting and balancing.

Additionally, we provide below a table with indicators of the optimal protrusion for tires of different diameters.

Large offset (15,35,40,45) and its increase using a spacer

The suspension of a truck or car is clearly standardized and calculated by the manufacturer and the designers developing it. However, if you approach this tuning wisely, then in the end the increased wheelbase of the car and its track can increase the stability of the car.

And also the wheels protruding beyond the edges of the car will be a plus when supplementing it with plastic modifiers. The main thing that a car enthusiast needs to clearly understand is that the service life for which a given wheel bearing is designed decreases in direct proportion to the difference in the distance of the displaced disk and the original one recommended by the manufacturer.

To increase the disc overhang, a so-called spacer element is used. It is installed tightly between the disc and the drum, or the hub, it all depends on the model and design of the car’s brakes. The dimensions of these elements are of great importance; there are several types:

• Thickness up to 6 mm is considered small, but often the length of the original mounting bolt is enough to properly fix the disc together with the iron spacer.
• Thickness up to 25 mm. they already have a centering hub, which eliminates the option of destabilizing the balancing of the wheel parameter. The car acquires notes of a sporty, aggressive character and the spacers installed on it are visually identified.
• The thickness of the spacer is from 25 to 50 mm, which is considered quite large. They are attached to the hub or drum not only with bolts, but also with studs. Bolts are recommended for VAZ cars, fastening with a stud for brands such as Niva or UAZ.

The spacer to increase the offset must be made of durable metal. Therefore, before a car enthusiast starts making them manually, it is worth considering the risks and consequences of their installation. Still, it is recommended by experts to purchase high-quality factory spacers and offset wheels, which will be made from the required grade of steel, and also meet all reliability and safety requirements. Naturally, when choosing and specifying the parameters of disks and spacers, it is worth taking into account the number of mounting bolts and their length.

Will it be a problem to install a disk whose offset does not correspond to the recommended one?

Yes. There are many reasons why the use of incorrectly selected products is not acceptable. First of all, this concerns the correct functioning of the suspension. By installing beautiful, but incorrectly selected wheels for your car, you risk running into problems.

It is known that all functional components of a vehicle have their own service life and are designed for a certain effort. By using a disc whose offset does not quite suit the design of the car, you thereby upset this balance, which leads to premature wear of suspension parts. It’s good if it’s just a reduction in the service life of some component - in this case it can simply be replaced. But if a breakdown occurs while driving, then sad consequences cannot be avoided.

Quite often, disc sellers neglect accuracy in relation to the offset value. Thus, they try to offer you a non-specific model, which may very likely not meet your aesthetic requirements, but show the maximum of products in order to increase the likelihood of purchase.

Effect of offset on wheel position

Too positive/negative offset: impact on the car

Excessive positive overhang can cause damage to the inner suspension and brake components at the inner edge. This can result in poor handling, making the vehicle unstable at speed. Sometimes friction occurs on the thin inner sidewall of the wheel, causing the tire to burst.

Too much negative offset can also result in poor handling due to additional stress on the suspension components. The steering wheel can tip back during hard cornering, causing unstable steering and a possible crash.

conclusions

• the ET parameter is one of the key geometric parameters of the disk, which is important to remember when choosing a new set of disks for your car;
• the offset can be negative, positive, zero - for each car model, the manufacturer sets its own value, as well as permissible deviations from it;
• It is not recommended to change the offset of the discs too much - this is fraught with disruptions in the operation of the suspension and chassis, can negatively affect the handling of the car and will automatically remove the car from warranty.

The video clearly shows how to measure the disc offset:

Forces acting on suspension elements

Absolutely any element of the suspension is subject to several multidirectional forces. And it is quite natural that this list increases with the complexity of the design, which is very different from modern machines. Therefore, we offer for consideration the simplest example, where the hub is attached to the body by means of a lever and a strut with a shock absorber (McPherson system).

The force exerted on the wheels is directed upward from the plane along which the car is moving, and the mass of the car is distributed between all wheels. In this case, the points of application of these forces are the centers of the tire contact patch area. And if we assume that the suspension and camber angles are in ideal condition, and the wheels are well balanced, then these centers will be located on the axis of symmetry of each wheel. It is in this place that the axis of the shock absorber strut should fall.

Everything else is simple. The acting force corresponds to the proportion of the car's mass attributable to the wheel. It is directed away from the ground and creates moments in the levers, wheel bearing, and struts with shock absorbers. In the first two cases it will be tension, and in the last case it will be compression. All these points are carefully calculated at the design and construction stage. Naturally, a safety margin is provided for each part, but it was already mentioned above that it is constantly decreasing due to the widespread desire to reduce production costs.

When the calculated offset changes, the forces change their magnitude and direction, because a decrease in offset expands the wheelbase, and an increase - narrows it. This entails a displacement of the steering axis and a change in the parameters of steering wheel rotation, moments of forces and vectors of their application. This aspect also negatively affects the wear resistance of tires, maneuverability and controllability of the vehicle. Taken together, all of these factors lead to the fact that the suspension is operated in a mode that was not intended by the automaker. The level of driving safety decreases, and the service life of most structural elements decreases sharply.

In conclusion, let's say the following. If a new wheel with an offset that does not coincide with the standard one easily fits on the hub of your car, this is not a reason to use it without fear. It cannot be said that the operation of vehicles in such equipment will be safe. Wheel spacers can be a solution, but only if the offset is greater than standard, and you were able to find suitable spacers, which is often very problematic.

The influence of wheel width and offset ET on driving characteristics

Every car owner who is thinking about installing a disc with a non-standard offset should think about the consequences, and in particular, what can happen after their installation, as well as what exactly the disc offset affects:

• Steering axis offset;
• Sudden wear of bearings ahead of schedule;
• A radical change from the previous factory handling;
• Changing the service life of tires and all suspension parts and components.

All these reasons are not just words; they are based on the laws of physics. After all, it is known that the mass of any four-wheeled mechanism is generally distributed over all its wheels. The point of application of force is directed at the base of contact of the road surface directly with the wheel.

Even if we assume theoretically that the chassis and suspension are absolutely in good working order, then the vector of the wheel axis will be laid through this base. The vector line of the car's shock absorber located in the strut is also directed to the same point.

Installing wheels with an offset offset will change the vector of these forces, and therefore their load. That is, the installation of non-regulatory wheels will change the appearance of the car, making it unique and inimitable, but the driving performance will deteriorate, and the wear of spare parts will increase significantly. Of course, if the manufacturer does not provide for such a replacement.

Disc offset 40 and 45: what is the difference

Disc offset, or as it is commonly referred to as ET, is one of its most important parameters, showing the distance between the area where the wheel rim is adjacent to the hub and its vertical plane, which is responsible for symmetry.

Thanks to this parameter, the car enthusiast can immediately understand whether the wheel will fit on his iron horse or not. But we will try to look at the example of disk offset 40 and 45 (what is the difference, possible deviations, etc.) in the article below.

How to calculate the indicator using the formula?

As mentioned earlier, by the ET indicator you can determine whether the selected “sneakers” will fit on the car or not. And this procedure is carried out according to the following formula: ET=A-B2, where:

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

The result can have three parameters: good, zero and bad. With the first result, there will be a small gap between the area where the wheel touches the hubs and the hubs themselves, which means that such a wheel will be ideal for this vehicle.

If the calculation according to the formula showed a zero result, then, in principle, such “sneakers” can also be installed on a car.

But, in this case, the above-mentioned clearance between it and the hubs will not be observed, which will significantly increase the load from the impacts received (if the wheel falls into a hole, or hits an uneven surface).

But with a negative projection, the wheel cannot even be installed on the car, since the hubs simply will not allow it to fit under the wheel arch.

Permissible deviations

We have already looked at what a protrusion is and how it is calculated. And before moving on to the question of what is the difference between the ribs ET 40 and ET 45, let's consider in advance the permissible deviations of this indicator in the table below:

Based on the table, you can understand that the answer to the question will depend on the size of the wheel rim offset: will the measured wheel fit on the car? Well, if you ignore this parameter, then the likelihood of throwing your money away will be very high.

Having found out what the permissible disc offset is and how to calculate it using the formula, you can safely move on to the next, most important question that many car enthusiasts are interested in: what is the difference between the ET 40 and ET 45 protrusions? And the answer will be the following: firstly, when installing a wheel rim with a smaller rib on a car, the load on its wheel bearings will increase slightly. And this, in turn, will reduce the wear resistance of parts, preventing them from serving their intended life.

However, if we compare the protrusion of 40 and 45 mm, then such a negative phenomenon will practically not be noticeable. But when comparing ET 20 and ET 50 rims, reduced wear resistance will make itself felt within 2-3 months. Well, in addition to this phenomenon, the stiffness of the suspension will also increase, due to the lack of play between the wheel and the hubs.

Secondly, the vehicle will have visual differences. Namely: when installing the ET 40 rim, the wheels will practically not stick out from under the arches of the car, while the ET 45 will make them stick out as much as 5 mm, which will be visually very noticeable.

But, unfortunately, it will not be possible to unanimously assert that such a change will be negative. After all, some car enthusiasts specifically choose wheels with a large protrusion (within the permitted limits) so that the wheelbase of the car appears wider. Otherwise, there will be no difference between disc offset 40 and 45.

This means that you can safely install both options on your machine without fear of any consequences.

Expert opinion

Despite the fact that a 5 mm deviation of the protrusion is not considered significant, car manufacturers persistently do not recommend that motorists install such “sneakers” on their iron horse.

And they argue this by saying that with a changed rim offset (different from that recommended by the manufacturer), the technical and dynamic qualities of the vehicle change significantly.

Well, in addition to this negative phenomenon there is also a reduced service life of the part, which does not correspond to the warranty.

But sellers have a completely opposite opinion on this matter. And they explain it by saying that it is very difficult to select a specific disc with an offset.

But given acceptable deviations, the range of shoes for cars increases significantly, which benefits both buyers and sellers.

Well, you can decide for yourself which ledge is suitable for your iron horse, based on the information provided above.

Manufacturers' recommendations

There is no consensus among automakers regarding the permissible deviation from the offset and some insist on full compliance with their recommendations, others allow the deviation within +/– 5 mm, and still others independently indicate several offset options. What is the reason for such a big difference in opinions?

Reduced wheel offset

The fact is that in a competitive environment, automakers are forced to save their resources, so the loads on all machine elements are calculated with extreme accuracy. So even a slight discrepancy with the declared characteristics can lead to damage to the part.

By the way, experts have calculated that if you reduce the disc offset by 50 mm, this will lead to an increase in the load on the suspension by 1.5 times more than normal. This also explains the difference in reach for cars of the same model, but with different modifications of power plants.

Acceptable table of deviations for the most common car brands (Mercedes, Toyota, UAZ)

Each specific car brand has its own permissible deviations, which are best not violated.

Sources

• https://kolesa.guru/diski/vylet.html
• https://krutigayki.ru/vylet-diska-chto-takoe-et-i-na-chto-on-vliyaet/
• https://mashinapro.ru/1794-vylet-diska-et.html
• https://autochainik.ru/vylet-kolesnogo-diska.html
• https://AvtoKart.ru/dvigateli/chto-znachit-vylet-diska.html
• https://motorstory.ru/care/diski/chto-takoe-vylet-diska-i-kak-ego-razmery-vliyayut-na-xarakteristiki-mashiny/
• https://BlackTyres.ru/informaciya/informatsija-o-diskah/kak-uznat-vylet-diska/
• https://wheel-info.ru/vylet-diska.html
• https://VoDetal.ru/instrumenty/vylet-diska-chto-takoe-et-i-na-chto-on-vliyaet-v-chem-raznitsa-vyleta-35-i-45.html
• https://www.avtogide.ru/v-dannoj-state-budet-rassmotren-takoj-parametr-kak-vylet-diska-et-na-chto-vliyaet-etot-parametr-i-na-skolko-mozhno- ego-menyat-kakie-budut-posledstviya-ob-etom-i-pojdet-rech-dalee-na-chto-vliyae.html

How to determine the permissible ET deviation for a disk

As a rule, each automaker dictates its own permissible deviations for disc offset, and they depend only on the design of the frame, suspension, calipers, wheel arches and other elements of the vehicle. This means that for each car caliper there is a certain indicator of compatibility of various sizes, expressed in the range from minimum to maximum ET in millimeters. So, below are the permissible deviation indicators for the 35 most popular car models in Russia:

As for Russian VAZs, these cars are universal with the exception of the iconic Niva. Thus, the ET dimension for these car models is mainly 35-38 mm, which also corresponds to many indicators of the world's leading automakers.

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Measurable indicators for calculating departure

From this table it can be seen that negative offset is a familiar parameter only for full-size SUVs, and the smaller it is, the more the wheels stick out on them, however, this gives them additional stability on very difficult sections of bad roads; plastic linings around the perimeter of the wheel arches are often as standard. In addition, these brands of cars have a reinforced suspension, a bolt pattern of at least 5x115, which is better than on passenger cars and absorbs bending moment.

Additional markings of disks and decoding of their designations

The parameters listed above are fundamental when choosing a wheel for a car. However, on some of them you can find additional inscriptions and markings. For example:

• MAX LOAD . This abbreviation means what is the maximum permissible load allowed for a particular wheel rim. Typically the number is expressed in pounds (LB). To convert a value in pounds to a value in kilograms, simply divide by a factor of 2.2. For example, MAX LOAD = 2000 LB = 2000 / 2.2 = 908 kilograms. That is, disks, like tires, have a load index.
• MAX PSI 50 COLD . In this particular example, the inscription means that the maximum allowable air pressure in the tire mounted on the rim should not exceed 50 pounds per square inch (PSI). For reference, pressure equal to one kilogram-force is approximately 14 PSI. To convert the pressure value, use a calculator. That is, in this particular example, the maximum permissible tire pressure should not exceed 3.5 atmospheres in the metric coordinate system. And the inscription COLD means that the pressure must be measured in a cold tire (before the car starts moving, including not under the scorching sun).
• FORGET . This inscription means that a particular disc was made using the forging method (that is, forged).
• BEADLOCK . This means that the wheel is equipped with a so-called tire locking system. Currently, it is prohibited to use such disks for security reasons, so they are no longer commercially available.
• BEADLOCK SIMULATOR . Such an inscription indicates that the disk contains a simulator of the tire fixation system. In this case, such disks can be used everywhere. In practice, this means that these disks are no different from ordinary ones.
• SAE/ISO/TUV . These abbreviations refer to the standards and regulatory bodies to which the discs were manufactured. On domestic tires you can sometimes find GOST values ​​or manufacturer specifications.
• Date of manufacture . The manufacturer indicates the corresponding production date in encrypted form. This is usually four digits. The first two of them mean the week in a row, starting from the beginning of the year, and the second two - the year of manufacture itself. For example, the designation 1217 indicates that the disc was manufactured in the 12th week of 2022.
• Country of manufacture . On some discs you can find the name of the country in which the product was manufactured. Sometimes manufacturers only leave their logo on the disc or simply write the name.

Markings on Japanese wheels

On some discs produced in Japan, you can find the so-called JWL marking . Translated from English, the abbreviation means Japanese alloy wheels. This marking is applied only to those discs that are sold in Japan. Other manufacturers may apply the appropriate abbreviation if desired. However, if it is on the disk, it means that the disk meets the requirements of the Ministry of Land, Infrastructure, Transport and Tourism of Japan. By the way, for trucks and buses the similar abbreviation will be slightly different - JWL-T.

There is another non-standard marking - VIA . It is applied to the disc only if the product has passed successful tests in the laboratory of the Japanese Transport Inspection. The abbreviation VIA is an officially registered trademark. Therefore, applying it to discs that have not passed the appropriate tests is punishable. Therefore, discs on which the indicated abbreviation is printed will initially be of very high quality and durable.

What parameters are affected by rim geometry?

The main geometric parameters of disks are their mounting length and diameter. Based on these parameters, specialists determine which tire sizes and options to use for a specific wheel model. As a rule, leading automobile tire manufacturers allow small changes in wheel width, usually from 0.5 to 1 inch. Thus, installing a wider disc is only possible in combination with discs with a larger diameter compared to the previous ones.

For example, if the car had tires of the 175/70 R13 version, then the increased ones would be 175/65/R14. This should be taken into account to increase the outer diameter of the car wheel, otherwise it will rub the wheel arch. In this case, the increase was +0.8 millimeters. It should also be understood that car manufacturers adjust a certain wheel size and speedometer readings, so after installing more “powerful” wheels, its readings will have a certain error.

As for the difference in diameters in places where special holes for mounting bolts are located, the permissible error in changing them should be no more than 0.1 millimeters. If this error exceeds this figure, they talk about the need to center the wheel by alternately tightening the mounting bolts (sometimes complete with special centering rings or spacers to increase the disc offset).

Otherwise, the drive simply will not fit into the wheel hub. If the diameter is less than the permissible limits, then the owner has the opportunity to drill using turning equipment.

How to choose a wheel rim

When choosing a particular disc, car owners often have a problem - how to choose the right disc in accordance with the available tires. Let's look at a specific example of tires marked 185/60 R14. The width of the rim, in accordance with the requirements, must be 25% less than the width of the tire profile. Accordingly, it is necessary to subtract one quarter from the value of 185 and convert the resulting value into inches. The result will be five and a half inches.

Please note that for wheels with a diameter of no more than 15 inches, deviation in width from ideal conditions is allowed by no more than one inch. If the wheel is more than 15 inches in diameter, then the permissible error may be one and a half inches.

Thus, after the above calculations, we can say that for a 185/60 R14 tire a disk with a diameter of 14 inches and a width of 5.5...6.0 inches is suitable. The remaining parameters listed above must be clarified in the technical documentation for the car.

The following is a table that summarizes information about standard (factory) installed disks acceptable by their manufacturers. Accordingly, for cars it is necessary to choose wheels with suitable parameters.

How to make the right choice of disks

It is now clear that changing the offset of the ET disc even by 5 mm leads to undesirable consequences. Therefore, the selection of wheel rims should be carried out taking into account the recommendations of the vehicle manufacturer, including the offset value.

Where do different parts come from for the same cars?

Quite often there are situations when different spare suspension parts are purchased for two cars that differ only in engine type. How can this be explained?

The thing is that designers, during the design of cars, calculate a large number of parameters. Based on the design of the vehicle, certain requirements are drawn up for individual components.

And since different engines differ in weight, the load on the suspension, in this case, will also vary.

Previously, manufacturers included a large margin of safety in components and assemblies. Unfortunately, in the modern automotive industry, much attention is paid to reducing production costs.

For this reason, the safety margin becomes smaller. Nowadays it is almost impossible to find a universal spare part and different components and elements of the same car brand, but with different parameters, go on sale.

The same can be said about disc failure. If earlier this parameter could not be taken into account, now this is not permissible.

Difficult choice

The modern automobile industry produces a large number of cars. For this reason, with the abundance of models, it becomes very difficult to choose the right type of rims and in accordance with the recommendations of the car manufacturer. Often, owners have to choose between beauty, quality and safety.

Most sellers can assure you that a slight deviation of +/- 5mm will not have a major impact on the vehicle's performance. Sometimes in reality this turns out to be the case, but there are a number of models for which this deviation is critical. Therefore, following the manufacturers' recommendations will avoid problems with the suspension.

Spacers as an alternative solution

But not everything is as bad as it might seem, since there is a solution - wheel spacers. They are produced in the form of flat metal pancakes, and are installed between the hub and the disk. That is, now you don’t have to worry if you purchased a set of wheels with the necessary parameters, but with an offset different from the standard value. The situation will be corrected by spacers of the required thickness.

Video - how to measure disc offset:

In addition, spacers can be useful if the number or position of holes for mounting bolts does not match. Some car enthusiasts use them to extend the wheelbase.

Spacers can be of different types:

• thin;
• average;
• thick;
• super thick.

Thin elements (3-10 mm) are suitable when the wheel slightly touches the suspension components. The middle ones have a thickness of 12-20 mm and can be with an additional centering hole. Thick spacers are 20-30 mm thick and help compensate for negative offset. Extra thick parts with a thickness of 30-40 mm. They are relevant for tuning an SUV.

Based on this, we can highlight the main tasks that can be solved using wheel spacers:

• fixing the crash to the recommended value;
• optimal solution in case of mismatched bolt holes;
• to expand or narrow the wheelbase by changing the offset value in one direction or another.

If you need to use spacers, you should choose only high quality products. Otherwise, individual components or the entire suspension will fail prematurely. This is at best, but at worst, the risk of an emergency cannot be ruled out, which can lead to various consequences.