Wheel hub introduction

2024-10-22

I. Definition

The hub is the part at the center of the wheel where the axle is installed. It is an important component that connects the brake drum (or brake disc), wheel disc, and axle shaft. In plain terms, it is the metal part inside the contour of a car tire and plays the role of supporting the tire and connecting the vehicle's suspension and other systems.

II. The structure of the hub

Rim
- This is the outermost part of the hub that directly contacts the tire. Its shape and size determine the tire installation method and the compatible tire specifications. For example, common rims include deep-drop rims and flat-base rims. Deep-drop rims are mainly used on small vehicles such as cars. Their edges are relatively deep and can well fix the tires. Flat-base rims are generally used on large vehicles such as trucks. Their structure is relatively simple and is convenient for installing and removing large tires.
Spoke
- The spoke is the part that connects the rim and the hub's central mounting plate and mainly plays the role of supporting the rim. The design forms of spokes are diverse. There are traditional multi-spoke designs. For example, some luxury car hubs may have more than ten spokes. This design not only ensures strength but also has good aesthetics. There are also minimalist designs with fewer spokes. For example, some sporty car hubs adopt 5 - 6 thick spokes, which can give people a sense of power. In terms of manufacturing technology, spokes can be cast or forged. Cast spokes have relatively low cost but slightly lower strength. Forged spokes have high strength and light weight but are more expensive.
Mounting plate
- The mounting plate is the part of the hub that connects to the vehicle's axle shaft. It has mounting bolt holes and the hub is fixed to the vehicle's axle shaft through bolts. Its size and the distribution of bolt holes (commonly known as PCD, i.e., pitch circle diameter) vary depending on the vehicle brand and model. For example, common PCDs include 4×100 (indicating 4 bolt holes with a pitch circle diameter of 100mm), 5×114.3, and many other specifications.

III. The materials of the hub

Steel hub
- Advantages: Low cost, good toughness, and can withstand large impacts. Widely used on some trucks and economy cars. For example, the steel hubs of some light trucks can effectively resist impacts from foreign objects such as stones in complex road conditions such as construction sites and are not easily damaged.
- Disadvantages: Relatively heavy, which will increase the unsprung weight of the vehicle, thereby affecting the vehicle's handling and fuel economy. Moreover, the heat dissipation of steel hubs is relatively poor. When braking for a long time, heat easily accumulates in the hub, affecting braking performance.
Aluminum alloy hub
- Advantages: Light weight. Compared with steel hubs, it can effectively reduce the unsprung weight of the vehicle and improve the vehicle's handling and acceleration performance. At the same time, aluminum alloy has good heat dissipation performance. In the case of frequent braking, it can quickly dissipate heat, which is beneficial to maintaining the performance of the braking system. In addition, the appearance of aluminum alloy hubs can be processed by various techniques such as polishing and electroplating, making it have good aesthetics and is widely used on various cars and SUVs.
- Disadvantages: Higher cost, and the strength is not as good as that of steel hubs. When subjected to a large external force impact, aluminum alloy hubs may deform or be damaged.
Magnesium alloy hub
- Advantages: Magnesium alloy is one of the lightest metal structural materials at present. It can further reduce the unsprung weight of the vehicle and improve the vehicle's performance. Its heat dissipation performance is also very excellent.
- Disadvantages: Expensive price, and the corrosion resistance of magnesium alloy is relatively poor. Special surface treatment is required to prevent corrosion. At the same time, the manufacturing process of magnesium alloy is complex and requires high production equipment and technology.
Carbon fiber hub
- Advantages: Carbon fiber material has extremely high strength and extremely light weight. It is an ideal material for high-performance vehicle hubs. It can greatly improve the vehicle's handling performance and acceleration performance, and the appearance of carbon fiber also has a sense of technology.
- Disadvantages: Extremely high cost, complex manufacturing process, and the impact resistance of carbon fiber material is relatively weak. Once subjected to a large impact force, it may be damaged.

IV. The size of the hub

Hub size is usually expressed in inches and mainly includes the diameter and width of the hub. For example, common car hub sizes are 15 inches, 16 inches, 17 inches, etc. The larger the diameter, the more atmospheric the overall appearance of the wheel looks. At the same time, the width of the hub will also affect the installation of tires and the driving performance of the vehicle. A wider hub can install wider tires, which can increase the contact area between the tire and the ground and improve the vehicle's grip, but it will also increase the vehicle's fuel consumption.

V. Key points for choosing a hub

Size matching
- Select the appropriate size hub according to the vehicle's brand, model, and tire specifications. If the hub size does not match, it may lead to improper tire installation and affect the driving safety of the vehicle. Generally, the vehicle's user manual will provide the suitable hub size range for the model.
Material selection
- Select the hub material according to your own needs and budget. If you focus on economy and durability, steel hubs are a good choice. If you pursue handling and aesthetics, aluminum alloy hubs are more suitable. For high-performance vehicles, magnesium alloy or carbon fiber hubs can be considered, but pay attention to their high price and special use requirements.
PCD and center hole size
- These two parameters must be completely matched with the vehicle's axle shaft and hub installation part. If the PCD does not match, the hub cannot be correctly installed on the vehicle. If the center hole size is inappropriate, it will cause eccentricity after the hub is installed, affecting the vehicle's balance and driving stability. When purchasing a hub, be sure to accurately understand the vehicle's PCD and center hole size. Usually, this information can be obtained from the vehicle's user manual or by consulting a car dealer.