Sway Bar (Anti-Roll Bar): What It Does and What a Failed Link Sounds Like

What Is a Sway Bar?

The sway bar — also called the anti-roll bar, stabiliser bar, or ARB — is a metal bar (usually hollow steel) that connects the left and right sides of the suspension on the same axle. Most NZ passenger cars have a front sway bar, and many have one at the rear too.

Its job is to reduce body roll when cornering. Without a sway bar, a vehicle leans significantly to the outside of a corner as weight transfers — which feels unsettling and compromises tyre contact with the road.

How Does the Sway Bar Work?

The sway bar connects to both sides of the suspension via sway bar links (also called drop links or end links), which attach to the struts or control arms. The bar itself runs across the car, usually fixed to the subframe or chassis via sway bar bushes (rubber mounting points).

When both wheels move up and down equally (straight-ahead driving), the bar just rotates in its bushes — it does nothing. But when the car corners:

• The outer suspension compresses (body rolls outward)
• The inner suspension extends
• The sway bar twists, opposing the difference — and that torsional stiffness resists the lean

The stiffer the bar (thicker diameter), the more it resists roll. Performance vehicles use thicker bars.

Sway Bar Components That Wear

Sway Bar Links (Drop Links)

The most commonly replaced component. The links connect the bar ends to the struts/control arms using small ball joints or rubber bushes. These absorb constant movement and wear over time.

Signs of worn links:

• Knocking or rattling noise from the suspension going over small bumps, speed humps, or rough roads — often described as a metallic "clonking"
• The noise is usually heard more on one side and is consistent with road speed and bump inputs
• Sometimes mimics ball joint or strut top noise — a mechanic will identify which component by checking for play

Worn links are one of the most common WoF failure items on NZ vehicles, especially on Japanese imports with high mileage.

Sway Bar Bushes

The rubber bushes that hold the bar to the subframe/chassis harden and crack with age. Failed bushes cause:

• A squeaking or creaking from the chassis — often heard when the car rolls in corners or over bumps
• Some additional body movement (the bar can shift slightly in worn bushes)
• Less dramatic than link failure but worth addressing

WoF Relevance

Worn or broken sway bar links are a common WoF failure in NZ:

• Excessive play in links is a steering/suspension system fault
• Loose or detached links can contact other components and cause further damage
• Inspectors check links for play and condition during every WoF

Sway bar bush wear is less likely to directly fail a WoF but may be noted as an advisory.

Can You Drive With a Failed Sway Bar Link?

A single failed link means the sway bar on that side is effectively disconnected. The result:

• Increased body roll, especially in corners
• Less balanced handling — the car feels more unsettled
• On motorway ramps or emergency steering situations, the increased roll is more noticeable and potentially hazardous

Not immediately dangerous at normal speeds, but it compromises handling and will fail a WoF. Don't delay — links are cheap.

NZ Cost to Replace

Sway bar links are a quick, inexpensive repair that meaningfully improves handling feel and ride quality. On many Japanese imports, renewing the entire sway bar system (links and bushes all round) for $400–$600 transforms the car's handling.

When to Book a Mechanic

• You hear a knocking or rattling sound over speed bumps or rough road surfaces — especially if it sounds like it's coming from the front suspension
• WoF inspection noted sway bar link play or wear
• The car feels like it rolls more in corners than it should
• General suspension service on a high-km Japanese import

Further Reading

• Find a mechanic near you
• Shock absorbers: how they work alongside the sway bar
• Ball joints: another source of suspension knocking
• Car suspension overview