The hub is one of the most important components of the chassis of any car, providing the transfer of torque from the engine to the wheels and their reliable attachment to the axle. It is this element that connects the movable part of the suspension with the wheel disc, taking on colossal loads during movement, braking and cornering. Understanding how it works front-wheelIt is necessary for each owner of the car for timely diagnosis of malfunctions and safe operation of the vehicle.
In modern cars, this unit is often assembled with a bearing, forming a so-called hub, which requires special attention during maintenance. Ignoring the first signs of wear can lead to the wheel jamming on the go or, worse, to its spontaneous separation from the axle. In this article, we will take a detailed look at the design, fault symptoms and replacement process so you can feel confident behind the wheel.
Design and operation of the node
Structurally, the hub is a metal part, most often made of high-strength steel or cast iron, having the shape of a cylinder with a flange. On the flange there are holes for fastening the wheel disc with bolts or studs, and inside the body is placed hub-bearer, providing free rotation around a fixed axis. In front-wheel drive cars, an external drive slit shaft (SRUS) often passes through the center of the hub, transmitting rotation from the gearbox.
The main task of the node is to minimize friction between the rotating wheel and the fixed axis or rotating fist. For this purpose, a rolling bearing (usually a ball double-row or roller conical) is used inside, which is lubricated with a special refractory lubricant and sealed with oil seals. Production technology The modern hubs can withstand axial and radial loads of several tons, which is critical for safety.
It is important to note that depending on the type of suspension (McPherson, multi-link), the design of the flange and the method of attachment may differ. For example, in some models BMW or Mercedes-Benz the hub can be integrated into the rotating fist, which complicates repair, but increases the rigidity of the structure. At the same time, on budgetary models Volkswagen or Renault Often used separate removable hubs, which are easier to replace.
⚠️ Warning: Never attempt to restore hub geometry after a strong impact on a curb or pit. The metal loses its strength and re-deformation can occur at any time, leading to an emergency.
Main signs of malfunction and wear
Determine that front-wheel It requires attention, and it can be long before the critical consequences occur. The first and most common feature is a characteristic hum or howl, which increases when you gain speed. This sound is often confused with the noise from the tire tread, however, the hum of the bearing has a constant tone and varies depending on the load on the axle when turning the steering wheel.
The second symptom may be the appearance of vibration on the steering wheel or on the body of the car, especially when braking. This suggests that the geometry of the seat is broken or the bearing has a significant backlash. It is also worth paying attention to the uneven wear of rubber, which often occurs due to the wrong angle of installation of the wheel caused by the destruction of the knot.
In the later stages of wear, heating of the wheel disc in the hub area may be observed. If you touch the central part of the disk after the trip and it turns out to be hotter than the rest of the areas, this is a direct signal that the lubricant in the bearing is dry or it will be pulled over. Visual inspection can also reveal damage to the protective anther or traces of lubrication on the brake pads.
Diagnosis: how to check the hub yourself
Checking the technical condition of the unit does not require complex equipment and can be performed in garage conditions. First, you need to lift the car on the jack so that the wheel being tested is torn off the ground. Take your hands on the top and bottom of the wheel (for 12 and 6 hours) and rock it from yourself and to yourself. The presence of a tangible backlash indicates wear hub-bearing or loosening the nut.
Next, spin the wheel with your hands and listen to the sound of rotation. The correct node rotates silently and smoothly, without jamming and metal crunch. If you hear a grinding or a discontinuity of the course is felt during rotation, the diagnosis is obvious. You can also ask the assistant to slowly spin the wheel while you hold your hand on the suspension spring or on the swivel fist itself - vibration from the collapsing bearing is well transmitted to the metal elements.
It is also worth checking the heating after a short trip. Walk a few kilometers in calm mode, then carefully (without touching the brake disc!) bring your palm to the center of the wheel. Compare the temperature of the left and right wheels of the same axle: the difference in heating indicates problems in the node from the hotter side.
When diagnosing backlash, be sure to make sure that the nut of the semi-axis is tightened with the right moment. Often, the “back of the hub” is simply a consequence of an untwisted nut after a previous repair.
Comparison of types of tarmac bearings
There are several basic types of bearings used in the automotive industry, and the choice of a particular option depends on the load and suspension design. Understanding the difference between them will help you choose the right parts and estimate the cost of future repairs. Below is a table comparing the main characteristics of the different types.
| Type of bearing | Load capacity | Resource (km) | Features |
|---|---|---|---|
| Ball radial | Medium | 80 000 - 120 000 | Quiet work, low friction |
| Conical roller | Tall. | 100 000 - 150 000 | It can withstand axial loads, requires adjustment |
| Two-row ball | Tall. | 120 000 - 180 000 | No maintenance, sealed. |
| The Hub Unit (Hub Unit) | Very high. | 150 000 - 250 000 | Integrated design, high price |
As you can see from the table, modern hub-knot Hub Units have the greatest resource, as they are designed as a single unit and eliminate the human factor in the assembly. However, their replacement is more expensive, as the entire structure in the assembly changes, not just the internal mechanism.
Step-by-step instructions for replacing the hub
Replacement front-wheel It requires special tools and certain skills. Before starting work, the car must be installed on a flat platform, fixed with recoil stops and raise the side with a faulty wheel. Be sure to remove the wheel and free access to the brake mechanism.
First, the brake caliper and disc are dismantled. To do this, the calipers are unscrewed, which is tied with a wire to the spring so as not to damage the brake hose. Then the brake disc is removed, opening access to the nut of the semi-axle. The central nut must be unscrewed with a powerful collar, often required to the moment of more than 200 Nm, having previously torn it off while the car is on wheels.
☑️ Preparation for hub replacement
After disconnecting the ball supports and the steering tip, the swivel fist is removed from the shock absorber rack. Pressing the old hub is carried out with the help of a hydraulic press or a powerful embroidery. Installation of the new part is carried out in reverse sequence, while the semi-axle nut must be replaced with a new one and tightened with a dynamometer key with the moment specified in the manufacturer's manual.
Should I change the wheel on the wheel?
Change the hub on the second front wheel "just in case" is not required. The resource of the nodes depends on the operating conditions and may differ. Change only the faulty assembly, but use the same manufacturer's parts for both wheels.
Frequent errors in repair and maintenance
One of the most common mistakes is to use a hammer to press a new hub. Shock loads destroy the bearing rolling tracks even before the start of operation, reducing its life many times over. Pressing must be carried out strictly by pressure on the inner or outer ring, depending on the design, using special mandrels.
Another mistake is the pull or underweight of the central nut. Excessive tightening moment will lead to overheating and jamming of the bearing, and insufficient - to the appearance of backlash and rapid destruction of the node. Use only. dynamometer to control the effort. Also, do not forget to clean the seat on the swivel fist from rust and dirt before installing a new part, otherwise the hub will get crooked.
⚠️ Warning: Do not allow dirt or sand to get inside the new bearing. Even microscopic particles of abrasive can bring an expensive knot out of action for several hundred kilometers.
The impact of operation on the detail resource
Term of service front-wheel It depends on the operating conditions of the car. Constant driving on broken roads, frequent hits on curbs when parking and aggressive driving style with sharp braking significantly reduce the resource of the site. Water and reagents, getting through the damaged anther of the SRUS or omentum, wash out the lubricant and cause corrosion.
To prolong the life of the chassis, it is recommended to avoid deep puddles at high speed, since the sharp cooling of the heated metal leads to microcracks. Regular washing of wheel arches and visual inspection of the condition of the anthers will help to identify problems at an early stage. Remember that a serviceable suspension is not only comfort, but also your safety on the road.
Timely replacement of the hub at the first signs of a hum costs 3-4 times cheaper than repairing a swivel fist or restoring after a wheel break at speed.
Can I drive if the hub is buzzing?
You can drive with a buzzing hub only to the nearest service in calm mode. Operation of a car with a collapsing bearing is dangerous: at any time, the wheel may jam or detach from the axle, which will lead to an accident.
What is the life of the bearing?
The average life of a high-quality hub is from 80,000 to 150,000 km. However, when driving on bad roads, this figure can decrease to 40,000-50,000 km. Chinese analogues often run no more than 20,000 km.
Do I need to make a break-up after replacement?
Yes, after replacing the hub or rotating fist, the angles of the wheel installation are inevitably violated. Adjustment of the collapse-convergence is mandatory to prevent the car from moving to the side and uneven wear of the tires.
Why does the scalp warm up after replacement?
Heating can be caused by nut pulling, improper pressing (skewing) or using poor-quality lubrication. Also, the cause may be friction of the brake caliper, if errors were made during installation.