When choosing a new shoe for their car, many people are faced with incomprehensible designations on the rim. Everyone understands the standard parameters: wheel radius, profile width, seasonality. But besides them, when buying, you need to take into account many other things: the diameter of the mounting hole, the offset of the disk, the location of the mounting holes. All these characteristics must match the parameters of your car. You can find out what is a PCD of a rim and how to choose the right new rims from this article.
The rim is one of the most important parts of a car. After all, it is the wheel that is responsible for traction. A lot depends on the tandem "tire - disk": the behavior of the car on the road, handling, fuel consumption and, finally, the most important thing - your safety. Needless to say, the choice of disks should be approached with special care?
BeforeTo buy wheels, you need to find out which ones are suitable for your car. This can be done by comparing the recommended parameters and numbers provided by the disc manufacturer. Here is an example of a disk marking: 8, 5Jx15H2 PCD5150 ET40 d54.1. At first glance, these figures are terrifying: how much should they represent?
The first number (8, 5) indicates the width of the rim. This parameter is necessary when selecting tires for wheels. The next one is the mounting diameter (15) - the size of the wheel rim for the tire. Next is the location of the mounting holes (5150). The first digit indicates the number of holes in the disc, and the second indicates the diameter of the circle on which the mounting holes are located. Disc offset (ET) can be either positive or negative. Manufacturers recommend that motorists strictly observe the disc offset recommended by the manufacturer. Otherwise, under load, the disk may simply break. The last is the diameter of the mounting hole, which is usually universal and suitable for several brands of passenger cars at once.
PCD – what is it?
In tire fitting you can often hear about the bolt pattern. What's this? Wheel PCD stands for Pitch Circle Diameter - the location of the mounting holes. In the people it is called simply - the parameters of the drilling of the disk. This is not the most important characteristic in wheels, but it is still necessary to know. Drilling involves the processing of a part using mechanical action. A special drill makes holes in the disk. their depth andthe location as well as the diameter play an important role in mounting the wheels. PCD indicates the diameter of the circle in millimeters on which the mounting holes of the wheel are located.
Today, there are quite a few ways to drill a wheel. Therefore, if you buy a non-original spare part, it is better to make sure several times that it is suitable for your car brand.
Disk drilling is a very specific parameter that many manufacturers put at the end of the list or do not indicate at all. And very in vain, because not only the diameter of the wheel affects the technical characteristics of the machine. The fact is that it is with the help of mounting holes that the disk is fixed on the hub. Even the smallest inconsistencies can lead to unpleasant consequences. Here are some of them:
- Beating machine.
- The wheel is off.
- Increased load on the car disk and its subsequent deformation.
That's why you need to remember that this is a PCD and be sure to consider it before buying discs.
PCD in practice
How is the selection of auto wheels in practice? For example, you have a Mazda brand car with a 5114.3mm mounting hole. Let's say you saw discs in the store that have parameters of 5111 mm. It seems that the number of holes is the same, and their size differs by only 3 millimeters. But these millimeters can play a sad joke on you. In expensive car models, which are usually installedalloy wheels, PCD diameter may vary by 0.5mm. There are also less noticeable differences. For BMW, PCD drilling has a parameter of 5120, and for Jaguar, the same figure is 120.6 mm. However, discs from one company will not work for another car. He can regularly drive them for more than one year, but the parts will gradually wear out, and the road will not be so smooth.
How to identify PCD
You can try to determine the bolt pattern of the disk yourself, by eye. But it is much better to do this with the help of special measurements, and even better - to transfer this matter into the hands of specialists. The number of mounting holes can be counted immediately. And to determine the diameter of the mounting holes, you need a caliper. In the most extreme case, you can also use a ruler or tape measure.
The formula used for calculation is PCD=const x N.
- N – distance between bolts;
- Const is a constant value depending on the number of bolts.
An important nuance is that you need to measure the distance from the side (extreme) walls of the holes.
Diameter for different brands of cars
If you are unable to determine the PCD parameters of the rim yourself, it would be best to check with the manufacturer for information. What are the PCD parameters for cars of different brands?
For new Audi models, the wheel bolt pattern is always the same and amounts to 5112 mm. On older models, the hole diameter is slightly smaller: 4108 (until 1995). The German manufacturer BMW has a permanentPCD size 5120. For Daewoo, popular on Russian roads, the bolt pattern depends on the model and ranges from 4110 to 4114.3. American Ford has a small PCD auto wheel size of 5108. But the VAZ becomes the champion, which stopped at the characteristic 498.
What else you need to know about drilling disc holes
The diameter of the center hole should ideally match the bore diameter of the hub. If these two parameters match, the wheel is pre-centered on the hub. In the future, this greatly facilitates the installation of the wheel and the tightening of the bolts. Centering is completed by checking the coincidence of the holes for mounting the wheel. If the parameters do not match, at the tire fitting you may be offered a way out - an eccentric. Its cone is freely movable, while one part is located in the mounting holes, and the other is installed in the hub mount. This measure can be taken to temporarily replace the discs, but it is not recommended to constantly use eccentrics.
Manufacturers usually make acceptable PCD drilling parameters slightly larger than the real ones. Because of this, it becomes even easier to make a mistake in choosing the right rim. To prevent this from happening, check with the manufacturers for information, and then measure yourself. Such a double method will protect you from annoying mistakes. For example, a disk with PCD 598 can be installed on a hub with parameters 5100. It would seem that two millimeters will not play a significant role. But as a result of this, only onenut of five. The rest will sit loosely or skewed on the hub.
The most important thing is to remember that it is possible to install rims on the wrong diameter, and the problem from such an act will not manifest itself immediately. But due to incomplete shrinkage, the wheel will imperceptibly wind from side to side, which in the end can lead to very serious consequences. Moreover, they will not be able to tell you about the problems even in tire fitting, since usually even specialists are not able to notice such minor deviations. If you plan to use adapter rings when installing disks, it is better to abandon this idea. Tampering with the structure of a machine can be downright dangerous.
How to choose the right disc
In addition to PCD, there are a number of other nuances that you need to pay attention to when choosing the right discs. You need to know the width and diameter, the size of the offset, the diameter of the car hub. The more closely these data will coincide with the recommended characteristics of manufacturers, the better. You can find out these parameters from catalogs or by self-measurement. If you decide to measure the characteristics of the disk yourself, be especially careful.
Unfortunately, for cars of different brands, all these characteristics can be quite different. Therefore, putting Mazda wheels on Ford is very imprudent. Even if they fit in diameter, the similarity will be limited to this. Wheels of different brands are very different from each other, which is why experts recommend buying only original wheels from trustedsuppliers.
PCD has a very strong effect on wheel fasteners. It is best to install wheels recommended by the manufacturer on the car. If this is not possible, try to choose disks with parameters that are as close as possible to them. So you protect your life and extend the life of the car's wheels.