Wheel Bearing: What It Does, What Noise It Makes, and What It Costs to Fix

What Is a Wheel Bearing?

A wheel bearing is a set of steel balls or rollers housed inside a metal ring (called a race) that allows your wheel to spin freely on the axle with minimal friction. Every vehicle has four wheel bearings — one at each wheel — and they carry the full weight of the vehicle while allowing the wheels to rotate at speed.

Modern vehicles typically use sealed hub bearing units that combine the bearing, hub, and sometimes the ABS wheel speed sensor into a single assembly. When they wear, the whole unit is replaced.

What Does a Wheel Bearing Do?

The bearing sits between the rotating wheel hub and the stationary axle or steering knuckle. It:

• Allows the wheel to spin freely with minimal friction
• Supports the vehicle's weight (radial load)
• Handles cornering forces (axial/thrust load)
• On many modern vehicles, houses the ABS wheel speed sensor ring

The Classic Sound: What a Bad Wheel Bearing Sounds Like

The most distinctive sign is a rumbling, humming, or growling noise that:

• Correlates with road speed (not engine speed) — louder at higher speeds, quieter at low speed
• Often sounds like driving on rough road surface even on smooth tarmac
• Changes when you sway side to side — the noise shifts as weight transfers between wheels
• Gets louder on a specific turn direction — if the noise increases when turning left, the right bearing is likely failing (weight shifts to the outside wheel)

This sway test is a useful DIY diagnostic: on a quiet road at around 80 km/h, gently sway the car left and right without changing speed. The noise will change noticeably when weight loads the bad bearing.

Other Signs of a Failing Wheel Bearing

• Loose or excessive play at the wheel — grab the top and bottom of the tyre with the car jacked up and try to rock it; more than slight movement suggests bearing or ball joint wear
• Vibration through the steering wheel (front bearing) or through the seat (rear bearing)
• Uneven tyre wear from a loose bearing allowing the wheel to run at a slight angle
• ABS warning light — on vehicles where the speed sensor is integrated into the hub unit, bearing damage can destroy the sensor ring

WoF Failure Risk

Wheel bearing condition is inspected during every WoF. Inspectors check:

• Wheel play when the vehicle is on a hoist (grab the wheel at 9 and 3 o'clock and at 12 and 6 o'clock to check for play)
• Noise during a road test

Excessive wheel play is a WoF failure — it affects vehicle stability and directional control. A badly worn bearing is a genuine safety hazard at highway speed.

What Happens If You Ignore It?

A worn wheel bearing that's ignored will progressively deteriorate:

• Increased play leads to tyre wear and alignment issues
• In severe cases, the bearing can seize or collapse entirely
• Complete bearing failure at speed can cause the wheel to wobble violently or, in the worst case, separate from the vehicle
• ABS sensor failure from bearing damage triggers the ABS warning light and disables ABS braking

Wheel bearing replacement is not optional once the bearing has significant play or loud noise.

NZ Cost to Replace

Note: If the ABS warning light appeared due to bearing failure, confirm the new hub unit includes the sensor ring (most aftermarket units do).

When to Book a Mechanic

• You hear a hum or rumble that correlates with road speed
• The noise changes when you sway the car side to side
• Your WoF has noted wheel bearing play
• Vibration is felt through the steering wheel at highway speed without a clear tyre-related cause

Further Reading

• Find a mechanic near you
• Ball joints: what they do and why they cause WoF failures
• Wheel alignment: why it matters for tyre wear
• ABS system: how it works and what the warning light means