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DISK PARAMETERS

Alloy wheels are one of the main parts that affect the appearance of the car. Made from lightweight aluminum alloys using injection molding technology. Alloy wheels have very high strength characteristics. Painted with special anti-corrosion paints and varnishes.
But not only this is the advantage of light alloys. There are other reasons to buy alloy wheels:
  • reduction of wheel weight and, as a consequence, weight reduction, improves acceleration dynamics, reduces the load on the engine and transmission, reduces fuel consumption, improves smoothness;
  • the use of a light-alloy wheel improves the cooling of the brake assembly, due to the high thermal conductivity of the alloy and better blowing due to its design;
  • The production technology of alloy wheels provides high accuracy, which minimizes the imbalance and, therefore, balancing can be carried out more accurately;
  • multi-layer coating ensures the protection of the wheels from the effects of the environment.
All discs have standard parameter marking.

The correspondence of the disk to the car is determined by the following main parameters:

A - seat diameter (measured in inches) - the diameter of the annular rim part on which the tire rests.

B is the landing width of the rim (measured in inches) - the distance between the inner surfaces of the side edges of the wheel. Determines the possible width of the profile of the installed bus
The tire profile width , a parameter directly related to the rim's landing width, has a significant effect on efficiency, dynamics, maximum speed, handling, braking distance. A wider wheel has a larger contact patch and, therefore, better road engagement, but there is a greater resistance to rolling and the flow of oncoming air. The result: the dynamics of acceleration is deteriorating, handling is improving.

ЕТ (departure) is the distance from the plane of the wheel adjacent to the hub to the plane passing through the middle of the rim fit width (measured in millimeters). For each car, the manufacturer provides a list of permissible wheel alignment options. It happens as a "positive" and "negative", the latter is found mainly in the SUV. Departure is not a constant value and, depending on the design features of the disc, can vary up to 10 mm for the same car. Most passenger cars have a projection between 30 and 40 mm.

With significant deviations departure from the recommended tires may hurt the wheel arches or suspension elements. In addition, the installation of wheels with a departure that is much smaller than that envisaged leads to a significant decrease in the stability of the vehicle in corners, increased steering sensitivity to road irregularities and uneven braking forces.

DIA - the diameter of the central hole should correspond (with a minimum gap) to the diameter of the centering protrusion on the hub of the car (measured in millimeters). The deviation of its value in the big party is allowed. In this case, adaptive centering rings (included in the set of alloy wheels) are used to install the wheel.
hump are small annular protrusions on the surface of the disk, made for a tubeless tire. In corners, they improve the fixation of the tire bead on the disc, thereby avoiding depressurization of the wheel.

PCD is the diameter of the centers of the mounting holes (measured in millimeters). This value should correspond to the standard, otherwise it is impossible to achieve reliable fixation of the wheel on the hub. A deviation of even 2 mm will cause the fastening elements (bolts) to skew.

PCD can be calculated by measuring the distance between the centers of the distant mounting holes (this can be done with a regular ruler without removing the wheels from the car)
  • For discs with four mounting bolts (or nuts), the PCD is equal to the distance between the centers of the far (opposite) bolts or nuts.
  • For discs with five mounting bolts (or nuts), the PCD is equal to the distance between the centers of the far (any non-adjacent) bolts or nuts multiplied by a factor of 1.051


For example: 6.5 J 15 5 × 114.3 ET45 d54.1  

6.5 - The width of the disk in inches. (B)
15 - Disc diameter in inches (D)
5 × 114.3 - The number of bolts (or nuts) in our case is 5. The diameter on which they are located,
called PCD (Pitch Circle Diameter) and in our case it is equal to 114.3 mm .
ET45 - Departure ( ET ) is measured in mm. and in our case it is equal to 45 mm .
d54.1 - Diameter ( DIA ) is measured in mm. and in our case it is equal to 54.1 mm .