Main parameters of wheel hub
1. Pitch Circle Diameter (PCD): It is a consistent installation parameter.
German cars are mostly 5-hole, such as BENZ which is generally 5×112mm, while BMW is mostly 5×120mm. Common Chinese car models have PCDs of 4/5×100/114.3mm.
Off-road vehicles often have a PCD of 6×139.7mm, and for high-displacement vehicles, a 5-hole configuration is more reasonable, such as Toyota's 4700 a PCD of 5×150.
2. Offset (ET): The distance between the hub bolt fixing surface and the geometric centerline (hub cross-sectional centerline) is simply the difference between the hub screw fixing seat and the overall wheel rim center point.
In simpler terms, it refers to whether the hub protrudes outward or retracts inward after modification.
For most cars, the ET value is positive, while for a few vehicles and some jeeps, it is negative.
For example, if a car has an offset value of 40 and replaces it with a hub with an ET value of 45, visually it will appear more recessed compared to the original factory hub.
Of course, the ET value not only affects visual changes but also relates to steering characteristics and wheel alignment angles of the vehicle.
A significant difference in offset values may result in abnormal tire wear, bearing wear, or even inability to install properly (brake system friction with hub prevents normal rotation).
In most cases, wheels of the same brand and style offer different ET values for selection before modification; comprehensive factors should be considered beforehand.
The safest approach is to maintain an identical ET value as that of the original factory without modifying brake systems.
When upgrading wheels, it is important to consider whether the wheel hub will interfere with the shock absorber inside or the fender outside.
An appropriate offset value ensures that there won't be any interference issues with the wheel hub; for example, Audi A8 original model has an ET value of ET38 for size 16x7.5 inches, ET35 for size 18x8 inches and ET30 for size19x8.5 inches.
3. X-Factor: Whether it will touch the brake disc; generally requires >27mm clearance.
4. Hub Hole (CB): Each car has different specifications; for example,BENZ usually has a hub hole diameter of around66 .6 mm ,while BMW typically has72 .6 mm. If the center hole on the wheel hub is too large,it must be used with hub centric rings. Otherwise,the vehicle may shake at high speeds.