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A wheel hub also known as a rim, steel ring, wheel, or tire bell, is a cylindrical metal component that supports the tire and is centrally mounted on the axle. Wheel hubs come in various types based on different diameters, widths, molding methods, and materials.

Development In the past, the most common bearings used in car wheel hubs were paired single-row tapered roller or ball bearings. With technological advancements, car wheel hub units are now widely used. The usage and quantity of wheel hub bearing units have been increasing and have developed into the third generation: the first generation consists of double-row angular contact bearings. The second generation features a flange on the outer raceway for easy installation by fitting the bearing onto the axle and securing it with a nut, making car maintenance easier. The third-generation wheel hub bearing unit combines the bearing unit with the anti-lock braking system. The wheel hub unit is designed with inner and outer flanges, with the inner flange bolted to the drive shaft and the outer flange securing the entire bearing assembly.

Types Wheel hubs are also known as rims. Depending on the characteristics and requirements of different vehicle models, the surface treatment of wheel hubs may vary. Generally, there are two main types: paint baking and electroplating.

For regular car models, less consideration is given to the appearance of wheel hubs, while good heat dissipation is a basic requirement. The common practice is to use paint baking, which involves spraying and then baking the paint. This method is cost-effective, provides vibrant colors, and maintains the appearance for a long time. Even if the vehicle is scrapped, the color of the wheel hub remains unchanged. Many Volkswagen car models use paint baking as the surface treatment technique. Some fashionable and dynamic colorful wheel hubs also utilize paint baking technology. These wheel hubs are moderately priced and available in various specifications.

Electroplated wheel hubs are further divided into types such as silver electroplating, water electroplating, and pure electroplating. Although silver electroplating and water electroplating wheel hubs have a bright and vivid color, they have a relatively short lifespan, making them cheaper in price. They are favored by many young people who seek novelty, with market prices ranging from 300 USD to 500 USD. Pure electroplated wheel hubs maintain their color for a long time, making them high-quality products with a higher price. Mid- to high-end sedans often opt for pure electroplated wheel hubs, which are priced around 800 to 900 USD.

 

Classification In the market, wheel hubs can be categorized into two main types based on material: steel wheel hubs and alloy wheel hubs, each with their own advantages and disadvantages.

Steel wheel hubs have the main advantage of simple manufacturing processes, relatively low cost, and strong resistance to metal fatigue. They are known for being affordable and sturdy. However, steel wheel hubs also have noticeable drawbacks. They have an unattractive appearance (or lack thereof), are heavy (steel material is much heavier than aluminum alloy for the same wheel hub), have high inertia resistance, poor heat dissipation, and are prone to rusting.

On the other hand, alloy wheel hubs can effectively address these issues. They have lighter weight, lower inertia resistance, high manufacturing precision, minimal deformation during high-speed rotation, which improves the straight-line performance of vehicles and reduces tire rolling resistance, thereby reducing fuel consumption. Alloy materials have about three times the thermal conductivity of steel, resulting in excellent heat dissipation. This contributes to thermal attenuation in the vehicle’s braking system, tires, and braking system. Original equipment manufacturer (OEM) alloy wheel hubs in the market are predominantly made of aluminum alloy. However, for many modified wheel hubs that aim to meet specific requirements or enhance visual appeal, elements such as chrome and titanium may be chosen as the base material. Nevertheless, compared to steel wheel hubs, alloy wheel hubs are more expensive, so they are often found as standard equipment in high-end models, while steel wheel hubs are used in lower trim levels of OEM vehicles.

 

The main advantages of steel wheel hubs are simple manufacturing processes, relatively low cost, and strong resistance to metal fatigue. However, they have clear disadvantages such as high weight, high inertia resistance, and poor heat dissipation.

 

Alloy wheel hubs have advantages such as lightweight, high manufacturing precision, high strength, low inertia resistance, strong heat dissipation capabilities, and good visual effects. However, they have complex manufacturing processes and higher costs.

    

Alloy wheel hubs are primarily made of aluminum, with the addition of metals such as manganese, magnesium, chromium, and titanium. Compared to steel wheel hubs, alloy wheel hubs offer energy-saving, safety, and comfort features. Consequently, an increasing number of vehicles have alloy wheel hubs as standard equipment. Let’s now look at the three main characteristics of alloy wheel hubs.

 

Energy-saving: Alloy wheel hubs are lightweight and have high manufacturing precision, minimal deformation during high-speed rotation, and low inertia resistance. This improves the straight-line performance of vehicles, reduces tire rolling resistance, and consequently reduces fuel consumption.

 

Safety: The thermal conductivity of aluminum alloy is about three times that of steel, resulting in excellent heat dissipation. This enhances braking performance, prolongs the lifespan of tires and brake discs, and effectively ensures the safety of the vehicle during operation.

 

Comfort: Vehicles equipped with alloy wheel hubs generally use low-profile tires that offer better cushioning and shock absorption than regular tires. This significantly improves comfort while driving on uneven roads or at high speeds.

 

Several Types of Alloy Wheel Hubs

Multi-piece Alloy Wheel Hubs Multi-piece alloy wheel hubs come in two-piece and three-piece designs. The various parts of the wheel hub are manufactured using forging and spinning processes and then connected with titanium bolts. These products are lightweight, high-strength, and superior in performance. However, they are expensive and primarily used in various championships and high-end luxury cars. In various levels of automotive and motorcycle racing worldwide, regardless of the conditions, vehicles are required to accelerate from 0 to 100 km/h within a short 3-second time frame. Therefore, wheel hubs need to withstand the extreme lateral acceleration, high operating speeds, and harsh conditions on the racetrack, as well as the impact caused by intense tire wear and resulting temperature rise. In this demanding environment, multi-piece aluminum wheel hubs have proven their resilience. Despite their lightweight construction, advanced manufacturing techniques and high structural strength give multi-piece designs a solid and robust appearance.

 

Single-piece Racing Alloy Wheel Hubs F1 racing cars require the use of single-piece wheel hubs. To ensure both the performance of the wheel hub and the weight reduction of the vehicle, a combination of forging and spinning processes is typically used for production. Compared to cast alloy wheel hubs of the same specifications, single-piece forged alloy wheel hubs exhibit more than an 18% improvement in mechanical performance while reducing weight by approximately 20%. Single-piece alloy wheel hubs designed and manufactured specifically for F1 racing have withstood various challenging environments. However, passenger car alloy wheel hubs do not have such stringent performance requirements as racing cars. Overall low-pressure cast alloy wheel hubs are sufficient to meet their performance needs. However, passenger cars place more emphasis on the appearance and aesthetic design of alloy wheel hubs. Influenced by motorsports and the demand for energy efficiency and aesthetics, automotive alloy wheel hubs are also undergoing changes. The main trends and directions of development include alloy wheel hubs with a sportier design, larger diameters, slender spokes, and lightweight construction.

Integrated Air Alloy Wheel Hubs To maximize the reduction of wheel hub weight, a new concept of lightweight alloy wheel hubs with integrated air cavities has emerged. This technology utilizes air cavity techniques to further reduce the weight of the wheel hub. These alloy wheel hubs come in single-piece and two-piece composite designs. The single-piece integrated air alloy wheel hubs incorporate air cavities in all the spokes and the inner and outer shoulders of the rim, significantly reducing the weight of the wheel hub by up to 20% compared to alloy wheel hubs with a similar structure. At the same time, the performance is greatly improved. The two-piece integrated air alloy wheel hubs feature air cavities in the inner shoulders of the wheel hub rim, reducing the weight of the wheel hub by 5% compared to alloy wheel hubs with a similar structure, while enhancing the performance of the product. This type of alloy wheel hub is manufactured using cast blanks and the spinning process to create the air cavities.

 

Manufacturing Methods There are three methods for manufacturing aluminum alloy wheel hubs: gravity casting, forging, and low-pressure precision casting.

1. Gravity Casting: Aluminum alloy solution is poured into the mold using gravity, and after forming, it undergoes lathe treatment and polishing to complete the production. This manufacturing process is relatively simple, does not require precise casting techniques, and has low cost and high production efficiency. However, it is prone to generate bubbles (sand holes), has uneven density, and lacks sufficient surface smoothness. Some models from Geely are equipped with wheel hubs produced using this method, mainly for early production models, while newer models have mostly switched to newer designs of wheel hubs.
2. Forging: A whole aluminum ingot is directly extruded and formed on a mold using a thousand-ton press. The advantages of this method are uniform density, smooth and delicate surface, thin wheel hub walls, lightweight, and the highest material strength. It is more than 30% stronger than the casting method. However, due to the requirement for sophisticated production equipment and a finished product rate of only 50% to 60%, the manufacturing cost is higher.
3. Low-Pressure Precision Casting: Precision casting is performed under a low pressure of 0.1 MPa. This casting method offers good formability, clear contours, uniform density, and a smooth surface. It achieves high strength, lightweight characteristics while controlling costs. Moreover, the finished product rate exceeds 90%. This method has become the mainstream manufacturing method for high-quality aluminum alloy wheel hubs.

Wheel Structure

1. Rim: The wheel part that is assembled with the tire, supporting the tire.
2. Spokes: The wheel part that connects and mounts the wheel hub to the axle, supporting the rim.
3. Offset: The distance between the center surface of the rim and the mounting surface of the spokes. It can be positive, zero, or negative offset.
4. Flange: The part of the rim that maintains and supports the tire’s direction.
5. Bead Seat: Also known as the mounting surface, it contacts the tire bead, supporting and maintaining the tire’s radial direction.
6. Drop Center: A groove on the rim with a certain depth and width, facilitating tire mounting and dismounting.
7. Valve Hole: The hole for installing the tire valve stem.

Basic Parameters A wheel hub consists of various parameters, and each parameter affects the vehicle’s usage. Therefore, before modifying or maintaining a wheel hub, it is important to confirm these parameters.

 

Dimensions The size of a wheel hub refers to its diameter. We often hear people mention “15-inch wheel hub” or “16-inch wheel hub.” The numbers 15 and 16 represent the size (diameter) of the wheel hub. In general, larger wheel hub sizes and higher tire aspect ratios can create a visually appealing tension and improve vehicle stability during handling. However, this can lead to increased fuel consumption as an additional drawback.

Width Wheel hub width, commonly referred to as J-value, directly affects tire selection. Even with the same tire size, different J-values result in varying tire aspect ratios and widths.

PCD and Bolt Pattern PCD, short for Pitch Circle Diameter, refers to the diameter of the circle formed by the bolts at the center of the wheel hub. Most wheel hubs have either a 5-bolt or 4-bolt pattern, and the distances between the bolts differ. Thus, you may frequently encounter terms like 4×103, 5×114.3, or 5×112. For example, in 5×114.3, the PCD of the wheel hub is 114.3mm, and it has 5 bolt holes. When selecting a wheel hub, PCD is one of the most important parameters. For safety and stability reasons, it’s advisable to choose a wheel hub with the same PCD as the original vehicle for upgrade and modification.

Offset Offset, also known as ET value (German: Einpresstiefe), represents the distance between the wheel hub’s bolt fixing face and the geometric centerline (centerline in the cross-sectional profile of the wheel hub). Simply put, it is the difference between the wheel hub’s center point and the fixing seat for the bolts. In popular terms, it refers to whether the wheel hub, after modification, protrudes outward or recedes inward. For most sedans, the ET value is positive, while for a few vehicles and some off-road vehicles, it can be negative. For example, if a car has an offset value of 40, and you install a wheel hub with an ET value of 45, visually it will appear more recessed within the wheel arch compared to the original wheel hub. However, the ET value not only affects visual changes but also relates to the vehicle’s steering characteristics and wheel alignment angles. A significant difference in offset values can result in abnormal tire wear, increased bearing wear, or even prevent proper installation (due to friction between the braking system and the wheel hub, preventing normal rotation). In most cases, the same wheel hub style from the same brand provides options with different ET values. Before modification, it is important to consider multiple factors, and the safest approach is to maintain the same ET value as the original one, assuming the brake system is not being modified.

 

Center Bore The center bore is the part used to securely connect the wheel hub to the vehicle. It refers to the position of the center of the wheel hub in relation to the concentric circle of the hub. The diameter of the center bore affects whether the installation of the wheel hub can ensure proper alignment between the wheel rim’s geometric center and the hub’s geometric center (although hub adapters can convert bolt patterns, such modifications come with risks, so users should exercise caution).

Selection Factors When selecting a wheel hub, three factors should be considered.

Size Avoid blindly increasing the size of the wheel hub. Some people may opt to increase the wheel hub size to improve vehicle performance. However, with the tire outer diameter remaining the same, a larger wheel hub would require wider and flatter tires. While it reduces lateral swaying and improves stability, making the vehicle agile during cornering, it also means thinner tire sidewalls and reduced shock absorption performance, sacrificing comfort. Additionally, the thinner the tire, the more susceptible it is to damage from road debris such as stones. Therefore, the cost of blindly increasing the wheel hub size should not be overlooked. Generally, increasing the wheel hub size by one or two inches from the original wheel hub size is most suitable.

Three Distances This means that when selecting a wheel hub, one cannot simply choose based on personal preferences for appearance but should also consider whether the three distances (parameters) are suitable based on the advice of technicians.

Shape Complex and intricate wheel hub designs may be aesthetically pleasing and give a sense of sophistication, but they are more likely to be rejected or incur additional charges during car washes because of the difficulty in cleaning them. On the other hand, simple wheel hub designs exude a sense of dynamism and are clean and neat. Of course, if you don’t mind the hassle, it’s also an option. Aluminum alloy wheels, which are currently popular, offer significantly improved resistance to deformation compared to traditional iron cast wheels. They are lighter, resulting in lower power loss and improved fuel efficiency. They also provide better heat dissipation, making them favored by many car owners. However, it’s worth noting that many car dealerships replace iron wheels with aluminum alloy wheels before selling vehicles to cater to customers’ tastes, but they significantly increase the price. Therefore, from an economical standpoint, when purchasing a car, it’s not necessary to focus too much on the wheel hub material. You can always replace them according to your own style and save some money in the process.

Installation Notes Please pay attention to the following points during the use and installation of wheel hub bearings:

To ensure maximum safety and reliability, it is recommended to regularly inspect the wheel hub bearings regardless of the age of the vehicle. Pay attention to early warning signs of bearing wear, such as any friction noise during rotation or abnormal deceleration when the suspension combination wheel turns. For rear-wheel-drive vehicles, it is recommended to lubricate the front wheel hub bearings when the vehicle has traveled 38,000 kilometers. When replacing the brake system, check the bearings and replace the oil seals.

If noise is heard from the area of the wheel hub bearings, it is important to first identify the location of the noise. There are many moving parts that can generate noise, and there may be contact between rotating and non-rotating components. If it is confirmed that the noise is coming from the bearings, they may be damaged and need to be replaced.

   3.

Because the working conditions that cause failure of both sides of the front wheel hub bearings are similar, it is recommended to replace them in pairs even if only one bearing is faulty.

   4.

Wheel hub bearings are sensitive and require the use of correct methods and appropriate tools in any situation. During storage and installation, the components of the bearings should not be damaged. Some bearings require significant pressure for installation, so specialized tools and reference to the vehicle manufacturer’s instructions are necessary.

    5.

When installing bearings, it should be done in a clean and tidy environment. Even small particles entering the bearings can shorten their service life. It is crucial to maintain a clean environment when replacing bearings. Hammering the bearings or allowing them to fall on the ground (or similar mishandling) is not allowed. The condition of the shaft and bearing seat should also be checked before installation, as even minor wear can cause poor fit and premature bearing failure.

  6.

For wheel hub bearing units, attempting to disassemble the wheel hub bearings or adjust the seal rings of the hub units can damage the seal rings, allowing water or dust to enter. Even the seal rings and inner raceways can be damaged, resulting in permanent bearing failure.

    7.

Wheel hub bearings equipped with ABS devices have a magnetic thrust ring inside the seal ring. This thrust ring should not be subjected to collision, impact, or contact with other magnetic fields. Before installation, remove them from the packaging box and keep them away from magnetic fields such as electric motors or power tools. When installing these bearings, observe the ABS warning needle on the dashboard during road tests to adjust the operation of the bearings.

  8.

For wheel hub bearings equipped with ABS magnetic thrust rings, to determine which side the thrust ring should be installed on, you can use a lightweight object near the edge of the bearing, and the magnetic force generated by the bearing will attract it. During installation, orient the side with the magnetic thrust ring inward, facing the sensitive components of the ABS. Note: Incorrect installation may cause the brake system to malfunction. 

   9.

Many bearings are sealed and do not require lubrication throughout their service life. Other unsealed bearings, such as double-row tapered roller bearings, must be lubricated with grease during installation. It is difficult to determine the amount of grease to apply due to variations in the internal cavity size of the bearings. The most important thing is to ensure that the bearings have sufficient grease. If there is excess grease, it will seep out when the bearings rotate. As a general rule of thumb, during installation, the total amount of grease should occupy 50% of the bearing clearance.

When installing locking nuts, the torque required varies greatly depending on the bearing type and bearing seat. Pay attention to the relevant instructions for reference.

 

Routine Maintenance Maintenance Methods Alloy wheels have gained popularity among private car owners due to their aesthetic appeal, safety, and comfort. Almost all new car models are equipped with alloy wheels, and many car owners have replaced their steel wheels with alloy wheels. Here, we will introduce the maintenance methods for alloy wheels:

 

When the wheel temperature is high, allow it to cool naturally before cleaning. Never use cold water for cleaning. Otherwise, the alloy wheel may be damaged, and the brake disc may deform, affecting braking performance. Additionally, cleaning alloy wheels with a cleaning agent at high temperatures can cause chemical reactions on the wheel surface, leading to loss of gloss and affecting their appearance.

 

If there is stubborn tar on the wheel, and regular cleaning agents are ineffective, you can try using a brush to remove it. Here is a tip for removing tar: Apply medicinal “Huo Luo You” and you may achieve unexpected results.

 

If the vehicle is in a humid area, it is important to clean the wheels frequently to prevent salt corrosion on the aluminum surface.

 

After thorough cleaning, you can apply wax to the wheels to maintain their shine.

 

When the wheel surface has stubborn stains that are difficult to remove, it is recommended to use professional cleaning agents. These cleaning agents are often effective in removing stains while minimizing damage to the alloy surface. Furthermore, alloy wheels have a protective layer, so it is crucial to avoid using paint polish or abrasive materials during cleaning. During driving, caution should be exercised to prevent scratches or damage to the wheels. If scratches or deformations occur, they should be repaired and repainted as soon as possible. So, how can scratches be repaired?

The specific steps for repair are as follows:

Step one: Inspect the scratch. If the scratch does not extend to the inside of the wheel, it can be repaired simply by wiping the area around the scratch with paint thinner to remove dirt.

Step two: If the deepest part of the scratch is difficult to clean, use a toothpick to thoroughly clean it.

Step three: To prevent unrelated areas from being painted, carefully apply masking tape around the scratch.

 

Step four: Prepare a fine brush and apply touch-up paint.

 

Step five: After painting, let it dry completely. Then, moisten waterproof sandpaper with soapy water and gently rub the surface to make it smooth.

 

Step six: After using waterproof sandpaper, use a polishing compound to achieve a glossy finish, and then apply wax.

 

If deeper scratches are present, the key is to observe whether the metal surface is exposed. If the metal surface is not visible, there will be no rust, and you can focus on applying touch-up paint. Apply the paint slowly with a fine brush and wait for it to dry completely. To prevent such situations, it is recommended to regularly wash the wheel rims, especially when the vehicle is newly used. Vehicles driven daily should have their wheel rims washed at least once a week. Wet them with clean water first, then use a sponge and cleaning agent to scrub, and finally rinse with plenty of water.

Regular maintenance is also essential. When the wheel temperature is high, allow it to cool naturally before cleaning. Never use cold water for cleaning, as it can damage the alloy wheels and even cause deformation of the brake disc, affecting braking performance. Additionally, cleaning alloy wheels with a cleaning agent at high temperatures can cause chemical reactions on the wheel surface, leading to loss of gloss and affecting their appearance.

When there is stubborn tar on the wheel hub that is difficult to remove, if regular cleaning agents are ineffective, you can try using a brush to clean it. However, avoid using a brush that is too hard, especially an iron brush, as it may damage the surface of the wheel hub. An expert has recommended a remedy for removing tar: using medicinal “huoluo oil” for wiping can achieve unexpected results. Car owners can give it a try. Additionally, when the vehicle is located in an area near the seaside, the wheel hub should be regularly cleaned to prevent salt from corroding the aluminum surface.

Misconceptions about modification:

Choosing counterfeit products for the sake of cheapness Modifying the wheel hub is an important step in car modification. Whether it’s for enhancing the appearance or improving handling performance, the wheel hub plays a significant role. A high-quality wheel hub undergoes rigorous manufacturing processes and strict inspections to ensure that its individual parameters meet the standards. Genuine wheel hubs are usually expensive. Currently, there are only a few domestic manufacturers that produce and sell (with export products) wheel hubs, so imported wheel hubs are relatively costly. Therefore, many modification enthusiasts choose so-called “domestic” or “Taiwanese” counterfeit wheel hubs to save costs. This is completely unacceptable. If the counterfeit wheel hub is produced by a “small workshop,” although it may not differ much from the genuine one in appearance, it falls far short in terms of weight, strength, and other safety indicators. Users often encounter unexpected cracks and deformations when using imitation wheel hubs, and these fake products are not capable of handling high-intensity loads during high-speed driving. If a high-speed rupture occurs, it directly affects the life safety of the driver and passengers. Therefore, it is important to note that if the economic conditions do not permit it, it is advisable to be cautious in choosing modified wheel hubs. Although the original “steel rim” or “cast wheel hub” may not be as aesthetically pleasing or lightweight, they at least ensure safety. In terms of wheel hub performance, the order is generally: forged wheel hub > cast wheel hub > steel wheel hub.

 

Not choosing the right wheel hub The wheel hub has a significant impact on enhancing the appearance, but when choosing a wheel hub, every detail should be taken into consideration. The various parameters of the wheel hub can affect its installation and the use with the vehicle. Incorrect PCD values may prevent proper installation, while incorrect ET values not only affect installation and use but may also impact future upgrade modifications. For example, if the original vehicle has a single-piston brake system and the owner plans to upgrade to a multi-piston brake system in the future, incorrect ET values and undersized wheel hubs may hinder proper installation. This means that when upgrading the brake system, additional expenses will be incurred to replace or upgrade the wheel hubs.

 

Incorrect installation of the wheel hub Many unscrupulous merchants providing modified wheel hubs do not inform vehicle owners about the size of the hub’s center bore. If this size is smaller than the original size, it will naturally be unable to fit. However, if the center bore size is larger without taking appropriate measures, it will cause eccentricity during vehicle operation, leading to abnormal noises and vibrations. In severe cases, it directly affects the safety of the vehicle. If you genuinely like a specific wheel hub but it happens to lack a suitable center bore size, you can consider either enlarging the bore or using centering rings provided by manufacturers to correct the issue.

Thinking that bigger wheels are always better Some people believe that upgrading means installing larger-sized wheel hubs, and others think that larger wheel hubs have a more visually impactful effect. However, whether it’s in terms of aesthetics or performance, it is important to choose a wheel hub size that is suitable for your vehicle, which is typically a moderate size. In terms of appearance, excessively large wheel hubs can make the vehicle appear top-heavy and affect the overall visual balance. In terms of performance, it requires a balance. When using larger-sized wheel hubs, it is necessary to upgrade the tires as well, choosing larger and wider tires. While wider tires provide better traction and stability, the increased friction can result in slower acceleration and higher fuel consumption. Moreover, when the wheel hub size is excessively large without adjusting other parameters, it significantly impacts the vehicle’s steering. Each vehicle has its limits when it comes to wheel hub size. If one blindly pursues size, it will require significant sacrifices in terms of performance and handling. Furthermore, considering cost-effectiveness, larger-sized wheel hubs made of the same material, such as alloy, come at a higher price, and the corresponding tire size also needs to be increased accordingly, leading to higher costs.

 

We are professional in forged wheels for many years, you can find more forged wheels as below.

 

 

 

May 17, 2023