Strut Bearing

Definition

A strut bearing is likely a component in the front suspension system of vehicles with strut-type designs, serving as the upper pivot point for steering. It allows the strut, which includes the shock absorber and coil spring, to rotate when turning the wheels.

Function and Use

Strut bearings enable smooth steering by allowing the strut to pivot, supporting vehicle weight, and absorbing road impacts. They are essential for ride comfort, handling, and stability.

Symptoms of Wear

Worn strut bearings may cause knocking noises over bumps, stiff or unresponsive steering, and uneven tire wear, potentially compromising safety.

Background and Definition

A strut bearing, also known as a strut support bearing, is a critical component of a vehicle's front suspension system, especially in vehicles with strut-type suspension designs. It is part of the strut mount assembly, which connects the suspension strut to the vehicle's body. The strut itself is a multi-purpose component that incorporates a built-in shock absorber, a coil spring, and acts as a structural member holding the tire in the correct position. The strut bearing specifically serves as the upper pivot point for the steering, allowing the strut to rotate when the wheels are turned to steer the car. This rotation is essential for smooth and precise steering, making the strut bearing a pivotal element for vehicle handling and safety.

Function and Operational Mechanics

The primary function of the strut bearing is to enable the strut to rotate during steering maneuvers, ensuring smooth and responsive steering. It acts as a bearing or bearing plate that facilitates this rotational movement, reducing friction and allowing the strut to pivot at the top while the bottom is attached to the suspension and steering components. Additionally, the strut bearing supports the vehicle's weight and absorbs vertical forces from road imperfections, contributing to ride comfort and stability. The strut mount , which includes the bearing, as a "sandwich" with insulating material in the middle, cushioning impacts to reduce noise and vibration transmitted into the vehicle. This dual role of supporting weight and enabling steering movement makes the strut bearing essential for both dynamic and static vehicle performance.

Types and Variations

Strut bearings are typically integrated into the strut mount assembly, and there can be slight variations in terminology and design. The Autodoc - What is a Strut Bearing and How Can I Tell if It’s Bad? clarifies the distinction: the strut bearing is the lower side of the strut mount, also called the support bearing, which lies directly on the suspension strut and provides the pivot point for rotation. The strut mount, in the broader sense, includes the upper part that connects to the dome in the wheel housing, responsible for returning the strut after steering maneuvers and cushioning noise and vibration. This distinction is important, as some sources use "strut bearing" and "strut mount" interchangeably, but technically, the bearing is the rotational component within the assembly. Most modern vehicles with strut suspensions, particularly front-wheel-drive cars, are outfitted with this type of system, where the strut acts as both a shock absorber and a structural member.

Historical and Modern Usage

Historically, strut-type suspensions have been common in front-wheel-drive vehicles since the mid-20th century, with the strut bearing evolving as a necessary component for steering in these designs. Modern applications include a wide range of passenger cars, SUVs, and light trucks, where strut bearings are critical for handling high loads and ensuring safety.

Advantages and Disadvantages

Strut bearings offer several advantages, as detailed in various sources:

1. Smooth Steering: They enable precise and smooth steering by allowing the strut to rotate, enhancing vehicle handling.
2. Noise and Vibration Reduction: As part of the strut mount, they help insulate tire noise and vibrations, improving ride comfort.
3. Compact Design: Strut-type suspensions, including the bearing, allow for a simpler, more compact design that is easier to assemble during production.

However, there are notable disadvantages:

1. Wear and Tear: Strut bearings can wear out from long-term use, corrosion, impact, or collision damage, leading to safety concerns.
2. Complexity in Replacement: Replacing strut bearings often requires disassembling the entire strut and spring assembly, which can be labor-intensive and requires specialized tools, as per KYB Americas.
3. Safety Risks: Worn strut bearings can compromise steering control, affecting braking distances and increasing accident risk.

Comparative Analysis with Other Suspension Components

Compared to other suspension components like control arms or bushings, strut bearings are specifically focused on the steering pivot point and rotational movement. Control arms, for instance, provide a pivot point for wheel movement but do not directly facilitate steering rotation, as seen in previous analyses of suspension arm kits. Strut bearings are unique in their integration with the strut mount, making them essential for vehicles with MacPherson strut suspensions, which are common in front-wheel-drive designs.

Practical Considerations and Maintenance

Maintenance involves regular inspection for signs of wear, such as knocking noises, stiff steering, or uneven tire wear. The Cars.com recommends replacing strut bearings whenever struts are replaced, typically in pairs, to maintain balance. After replacement, a wheel alignment is crucial to correct any misalignment, as worn bearings can cause alignment issues. Symptoms of a worn strut mount, including the bearing, include clunking noises, vibration, loose or stiff steering, and visual signs like cracked rubber or corrosion, as listed in KYB Americas.

Summary Table: Strut Bearing Characteristics