How to determine the departure of the car disk
There are several parameters, according to which car owners select "shoes" for their vehicles. For a car, these can be alloy wheels of small diameter, for SUVs - massive wheels with deep tread. The width of the rim also plays a role in the choice, the number of bolts for mounting to the hub, material, from which the product is made. But there is another parameter, which is often overlooked by many car owners. It was called departure. But how to determine the departure of the car's disk, to select the most suitable part for a particular vehicle model? This will be discussed in this article.
Disc characteristics
Many believe, that if the wheel has the required number of mounting holes, then it is by default suitable for installation on the car. This is not quite true. Of course, to install such a product on the hub will not be difficult, the drive will be securely fixed and will allow you to fully enjoy a comfortable ride. Moreover, in most stores, specializing in the sale of tires and wheels, to assure you, what is the size of the departure, declared by the manufacturer, does not affect anything, therefore does not play a fundamental role in choosing a wheeled product.
Determination and method of calculating the departure of the discs for the car
Departure refers to the geometric parameters of the disk. It characterizes the distance between the plane of application of the disk to the hub and the vertical center line of the wheel and is measured in millimeters. It would seem, to calculate this figure is quite problematic, but this will require determining and measuring only two quantities:
- The distance between the plane of the disk (internal) and plane, which disk is attached to the hub (a);
- Disk width in millimeters (b).
The formula for calculating the departure in general is as follows:
ET = a-b / 2
Geometric disk parameters
It is worth understanding, that this indicator provides information on the width width between the centers of symmetry of the wheels of the wheelbase of the car. This parameter is specified by the manufacturer in the technical documentation for the vehicle, and non-compliance with its stated may adversely affect the performance of the car.
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If in the process of calculating the departure of the disk was a negative value, that does not mean in any way, that the calculation was made incorrectly. This parameter can take values:
- Positive (the most common option);
- Negative;
- Zero.
So, for the convenience of buyers, wheel manufacturers have developed special markings. An ETXx code is applied to the inner surface of the disk, which allows you to judge the size and type of departure. About that, that this figure is negative, will indicate the inscription of the type ET-20, if the value of the parameter is positive, then the code will look like ET15. Marking ET0 means, that the selected disk has zero departure.
Disk departure scheme
Will disk installation be a problem, departure which does not correspond to the recommended
So. There are many reasons, on which operation of incorrectly picked up products is not admissible. First of all it concerns correct functioning of a suspension bracket. Setting even beautiful, but incorrectly selected car wheels, you run the risk of encountering problems.
It is known, that all functional units of the vehicle have their own service life and are designed for a certain effort. Using the disk, departure of which does not quite fit the design of the car, you are upsetting that balance, which leads to premature wear of the suspension parts. All right, if it is just a reduction in the service life of a node - in this case it can simply be replaced. But if the breakdown occurs in the process of movement, then sad consequences are inevitable.
Disc sellers often neglect the accuracy of the size of the departure. So, they are trying to offer you a vague model, which may not meet your aesthetic requirements, and show the maximum number of products, to increase the probability of purchase.
Influence of departure on wheel position
Need different parts for different configurations of the same car model
A huge number of people are working on creating one car - from designers to cabin assemblers. Of course, special attention is paid to the chassis. Hundreds of parameters are taken into account in the process of its development, each of which will determine the requirements for the design of individual elements.
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Today there are many brands of cars on the car market, and models - even more. The situation has become quite common, when the manufacturer launches the model, which differ only in engine capacity. It would seem, components for them must also be the same, but this is not the case. Many details may differ, including:
- Levers;
- Ball bearings;
- Silentblocks;
- NRT and others.
Such decisions are quite natural. The smallest difference in the mass or dimensions of the motor affects the distribution of forces, affecting 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 used to be the creation of a good margin of safety for the leading components of the car. Now this approach is a thing of the past, giving way to accurate calculations, due to which a significant reduction in the cost of development and manufacture of vehicles is achieved.
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