What are hubs and what are they for


The car hub is an important part of the chassis. During operation, it takes on heavy loads, and also provides a reliable connection between the wheel and the suspension and brake parts. Let's take a closer look at what hubs are, their structure and troubleshooting.

What is a hub

The hub is the assembly that connects the bearing part to the suspension for free wheel rotation. The principle of operation is carried out by bearing rollers that allow the wheel and brake disc to rotate. Due to the bearing, the wheel has the ability to rotate. Depending on the modification, the hub can be integrated with the brake disc and drum. Also, the hub can include an ABS sensor, studs for fastening the wheel, ABS comb. Simple hub modifications are made separately from the bearing.

What is the hub for?

Regardless of the make and model of the car, each wheel "sits" on the hub. This allows the wheel and brake disc to rotate relative to the steering knuckle or beam using a bearing. In the case of driving wheels, the hub transmits torque through the axle shafts, for this there are special splines in it, where the gearbox drive (output shaft) is inserted.

Hub device

What are hubs and what are they for

Considering the fact that the hub operates under high load, its housing is made from a durable cast “blank”. The dimensions of the hubs and the degree of strength are calculated when creating a car, which takes into account the weight of the car, the size of the wheels, and the speed characteristics. The hub is structured as follows:

  • rounded body has threaded holes for attaching to a beam or steering knuckle;
  • outside the hub unit there are holes for wheel bolts or studs, which are mounted into the unit by pressing;
  • the bearing, as a rule, is a double-row roller, tapered bearings (large and small) are less common;
  • the presence of a comb and a wheel rotation sensor (for the ABS system);
  • bearing fastening (the inner part is pressed into the cage or the outer part).

Types of hubs and bearings

What are hubs and what are they for

In wheel bearings, the rolling element is ball or tapered rollers. According to the degree of load, the bearing can be single-row and double-row. Often tapered rollers are single row due to the use of two bearings in the hub (small and large). Double-row bearings are widely used due to their high strength and reliability, which means that their resource can reach hundreds of thousands of kilometers.

Tapered bearings - serviced, need periodic renewal of high-temperature grease, it is imperative to have a protective cover to prevent dirt and moisture from entering. Periodic adjustment is required by tightening the hub nut.

Double row bearings - unattended. Most often they change with the hub. The bearing is closed on both sides with a plastic cover for reliable tightness. Cannot be adjusted, replacement is required if backlash occurs.

Hubs are divided into three categories:

  • for non-steered driving wheels - mounted on the rear axle of a car, rigidly connected to the axle stocking or steering knuckle. Has internal splines for the axle shaft, which is clamped with a nut to the hub;
  • for non-steered driven wheels - (front-wheel drive) are mounted on the rear axle by attaching to a beam or trunnion. The type of bearings and hubs depends on the modification of the car (it can be one piece with a drum or brake disc). Differs in a simple design;
  • for driving steered wheels - is a unit attached to the steering knuckle. It has a slotted hole for the axle shaft, possibly the presence of an ABS sensor. On modern cars, the hub is maintenance-free.

Causes and signs of hub breakage

What are hubs and what are they for

During the operation of the machine, the hubs tend to wear out for the following reasons:

  • natural bearing wear;
  • installation of larger wheels than recommended by the manufacturer (low rubber profile, large disc width);
  • operation of a car on a bad road surface (the hub unit takes impacts);
  • poor quality product;
  • strong or weak tightening of the hub bolt or nut.


  • increased noise from the worn-out unit;
  • the car goes off track;
  • increased vibration when driving.

It is extremely important to identify the bearing failure in time, otherwise it will lead to its seizure, which is extremely dangerous at high speed!

Tips on how to identify and diagnose a problem?

A sure sign of a hub malfunction is a strong hum coming from a speed of 40 km / h. The hum increases in intensity in proportion to the speed. The car must be sent for diagnostics, where, by hanging the wheel, rotating movements, as well as jerks, they will determine the side and the degree of wear. You can swing the wheel yourself by hanging the car with a jack.

Replacing the hub is not difficult if it is a single unit with a bearing. It is enough to remove the wheel, unscrew the two screws securing the brake disc, and unscrew the hub from the steering knuckle. Possible difficulties arise in the presence of an ABS sensor (the connector tends to sour).

Extending the life of the hubs is simple:

  • serviced units in a timely manner to adjust and renew the lubricant;
  • try to avoid pits and bumps;
  • brake correctly in front of obstacles (speed bumps, etc.), unloading the suspension;
  • install wheels of the appropriate size;
  • avoid substandard parts;
  • monitor the wheel alignment, as well as the serviceability of the chassis as a whole.



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