Trailing Arms

Trailing arms are suspension links that help locate a wheel or axle in the fore-aft direction while transferring acceleration and braking forces between the suspension and vehicle structure. Depending on the suspension design, they may also be described as lower links or control arms.

Both fixed and adjustable trailing arms can be used within different suspension layouts. Adjustable designs provide an additional way to correct suspension geometry after changes such as lifting or lowering where the original arm position no longer produces the required axle or wheel geometry. The correct arm depends on its position, mounting arrangement and role within the complete suspension system.

What Is a Trailing Arm?

A trailing arm is a suspension link that generally runs in a fore-aft direction between a wheel or axle assembly and a mounting point on the vehicle structure. It helps locate the suspension longitudinally while allowing controlled vertical movement.

The exact arrangement varies considerably between suspension designs.

On a linked solid axle, trailing arms or lower links can locate the axle front-to-back and help control its rotation. On independent suspension, a trailing arm may locate an individual wheel assembly.

The term therefore describes the component's general orientation and function rather than one universal arm design.

What Do Trailing Arms Do?

Trailing arms control fore-aft suspension movement and transfer longitudinal forces generated during acceleration and braking. Depending on the suspension layout, they can also influence axle rotation, wheel position and important suspension geometry.

Their functions can include:

• Locating the wheel or axle longitudinally
• Resisting acceleration and braking forces
• Controlling unwanted fore-aft movement
• Helping control axle rotation
• Influencing pinion or caster geometry on applicable designs
• Maintaining the intended relationship between suspension mounting points

Because trailing arms perform a locating function, unwanted movement from worn bushes, damaged joints or a bent arm can affect more than just ride noise.

What's the Difference Between a Trailing Arm and a Control Arm?

A trailing arm can be a type of control arm, but the terms are not always interchangeable. ?Control arm? is a broad description for suspension arms used to locate and control wheel movement, while ?trailing arm? more specifically describes an arm that runs generally fore-aft.

This is why some components may be described as rear lower control arms in one application and trailing arms or lower links in another.

Rather than relying only on the name, identify the component by:

• Its position in the suspension
• Its mounting points
• The direction in which it runs
• Whether it locates an individual wheel or a solid axle
• The geometry it controls

This is particularly important when selecting replacement or adjustable arms.

Why Fit Adjustable Trailing Arms?

Adjustable trailing arms allow the effective arm length or suspension relationship to be changed, providing a way to correct geometry where the standard arm cannot achieve the required position. They can become useful after ride-height or other suspension changes alter the resting geometry.

Adjustment should be based on the actual suspension setup rather than assuming every modified vehicle needs adjustable arms.

After a Lift or Lowering

Changing ride height alters the resting position of suspension components.

On a linked solid-axle suspension, lifting or lowering can change the angles of the locating links and affect the axle's relationship with the chassis. On other suspension designs, ride-height changes can alter wheel position and alignment geometry.

An adjustable arm allows the technician to alter the relevant link length where correction is required.

The amount of adjustment should be determined from measurements and the complete suspension geometry rather than lift or lowering height alone.

Pinion and Caster Angle Correction

On applicable solid-axle designs, changing the effective length of suspension links can rotate the axle housing.

At the rear, this can influence pinion angle, which affects the operating relationship between the differential and driveshaft.

On suspension systems where trailing or radius-type links locate a steering axle, changing arm geometry may also influence caster.

These adjustments interact with other suspension measurements. Correcting one angle without considering the complete setup can create another geometry problem, so adjustable arms should be set as part of a properly measured suspension configuration.

Front or Rear Trailing Arms: Which Do You Need?

Whether a front or rear trailing arm is required depends entirely on the vehicle's suspension design and the position of the arm being serviced or corrected. Trailing-arm terminology can apply to links at either end of a vehicle.

Rear trailing arms are common across several solid-axle and independent suspension layouts. Some linked solid-axle designs can also use fore-aft locating arms at the front.

A front trailing arm, rear trailing arm or lower trailing arm should not be selected based on appearance alone. Mounting dimensions, bush or joint arrangement, arm length and suspension function all need to match the application.

What Are the Signs of Worn Trailing Arms or Bushes?

Worn trailing arm bushes or damaged arms can allow unwanted suspension movement, potentially contributing to clunks, changes in wheel or axle location and inconsistent handling. These symptoms can also be caused by other suspension or drivetrain components.

Signs worth investigating include:

• Clunking during acceleration or braking
• Knocking over changes in the road
• Visible deterioration in arm bushes
• Excessive movement at mounting points
• Changes in wheel alignment
• Rear-end movement or wandering
• Uneven tyre wear
• Visible bending or physical damage to an arm

A damaged arm and a worn bush are different faults. If the arm itself is bent, cracked or otherwise structurally damaged, replacing bushes alone will not correct the problem.

Other Causes to Rule Out

Similar symptoms can result from:

• Panhard rod bush wear
• Worn control arm bushes
• Ball joint or tie rod wear
• Worn shock absorbers
• Wheel bearing problems
• Loose suspension hardware
• Tyre problems
• Driveline movement

Have the complete suspension inspected before replacing trailing arms based on symptoms alone.

Can Trailing Arms Help With Wheel Hop?

Trailing arms can influence wheel or axle movement during acceleration, so their condition and mounting compliance may contribute to wheel hop in some suspension layouts. However, replacing or upgrading trailing arms is not a universal cure for wheel hop.

Wheel hop occurs when tyre grip and suspension or driveline movement create a rapid cycle of loading and unloading.

Possible contributors include:

• Suspension bush compliance
• Shock absorber control
• Tyre grip and pressure
• Axle or wheel movement
• Drivetrain movement
• Suspension geometry

A more controlled trailing-arm arrangement may reduce unwanted movement where that movement is part of the cause, but the complete suspension and drivetrain should be assessed before deciding on a solution.

How Are Trailing Arms Fitted?

Trailing arm installation generally involves safely supporting the vehicle and relevant axle or suspension components, removing the existing arm and installing the replacement between its specified mounting points. Adjustable arms also need to be set correctly for the required suspension geometry.

What the Job Involves

Depending on the suspension design, installation may involve:

• Safely raising and supporting the vehicle
• Supporting the axle or relevant suspension components
• Removing the existing arm and mounting hardware
• Inspecting the mounting points, bushes and fasteners
• Setting an adjustable arm to an appropriate initial length
• Installing the replacement in the correct orientation
• Checking suspension and driveline clearances
• Settling the suspension at normal ride height
• Setting the required geometry
• Tightening fasteners to the manufacturer's specification

Where compliant bushes are used, follow the applicable procedure for final tightening. Some bush designs should be tightened at normal ride height to avoid unintended preload.

Safety and Wheel Alignment

Never work underneath a vehicle supported only by a jack. Use appropriate stands or workshop lifting equipment and ensure the axle or suspension remains controlled while a locating arm is disconnected.

Do not assume removing one arm at a time is appropriate for every suspension design. Follow the applicable workshop procedure.

A professional wheel alignment should be completed where trailing-arm replacement or adjustment affects wheel geometry. On solid-axle setups, other measurements such as axle position, caster or driveline angles may also need to be checked depending on the arm's function.

Use a qualified technician if you do not have the equipment or experience required to safely support and adjust the suspension.

Choosing Trailing Arms for Your Vehicle

Choose trailing arms according to the suspension design, front or rear position, mounting arrangement and geometry that needs to be maintained or corrected.

For an adjustable setup, determine the required change from actual suspension measurements rather than choosing an arm solely because the vehicle has been lifted or lowered.

Whiteline can assist with fitment if you're unsure which trailing arm suits your suspension setup.

Shop Trailing Arms with Whiteline

Whiteline trailing arms and adjustable trailing arms provide application-specific solutions for suspension location and geometry correction.

Need just one side? See individual trailing arms.

Choose the correct fitment with the added confidence of Whiteline's Fitment Guarantee, warranty and 60 Day Returns, with fitment assistance available when you need help identifying the appropriate trailing arm for your vehicle.