Understanding bmw ops Wheels

The  bmw ops  wheels mainly consists of two parts (hereinafter alloy wheels, for example). The first part is the wheel rim, the second part is the spokes. The former general shape, such as cylindrical, while the latter image Variety. Rim in contact with the tire, the seal, to withstand the force to the spokes and from the tire, after the spokes to the vehicle chassis.
Rim molding method, commonly one or two-piece or three-piece wheels. As the name suggests, the one-piece rim wheel rim and spoke one-piece, two or three-wheel rim and spoke the final shape of screws or welding, they can cast (production rims or spokes of a term, forging versa) + forging or forging + forging, etc. is not method combined works of greater flexibility, achievable objectives are higher, for example, the use of multi-chip type to lower rim weight, with a wheel rim can make a difference the OFFSET different spokes shape, similar to the intention of these split brake disc.
Wheels advanced production technology, manufacturers do not have pre-common (alloy wheels, about the rise of the 1970s) in the rim casting its specifications cast in the rim edge of the practice, and now we often round one or more labels circles are glued on the body, which illustrate some relevant values ​​of the rim, for example, such as 18 * 8.0J (or JJ), 114.3, +38, etc. The following figure Xiangjie.A: rim width (distance of the contact position with the tire rim)
B: rim diameter (in inches as a unit)
C: wheels mounting surface diameter (spoke with Automotive croissants contact position)
D: Center hole diameter (spoke with the position of the center of the car croissants contact hole. Sometimes wheels may not be  bmw ops  entirely consistent installation models, can find the center washer help part wheels accessories bag provides a central gasket.)
: Rim centerline (rim center of the cross section)
OFFEST (ET): the rim mounting surface and the rim centerline distance. As shown, OFFEST + / - the value of the points, the more outward precisely the greater the negative and vice versa. So everyone can easily understand the mean of said above +38.
The following figure also about J, JJ, and PCD's instructions.J, JJ: more common, representing two rim cross-sectional shape. Can also be seen in Figure J and JJValue to comply with industry standards. B, K, etc. rim sectional shape, but is less common.
The picture shows the typical multi-piece rim constitutes methods. The inner side of the rim, the outer rim, the spokes can be made in different ways, help to reduce the rim weight.
For manufacturers, this approach means that they work with a variety of the OFFSET variety of "J the number of" multiple spokes shape  bmw ops  of the wheels, reducing costs.