Harley-Davidson® Wheel Bearings Explained: Wear, Inspection and Common Symptoms

Wheel bearings are components most riders rarely think about — until something goes wrong.

They allow the wheels to rotate smoothly while supporting the weight of the motorcycle and coping with forces generated by cornering, braking and road impacts. They may be relatively small components, but their condition is critical to the motorcycle's handling and safety.

Modern sealed wheel bearings can provide a long service life with very little routine attention. However, contamination, corrosion, incorrect installation and simple wear can eventually cause problems.

Here's what Harley-Davidson® owners should know.

What Does a Wheel Bearing Actually Do?

A wheel bearing allows the wheel to rotate around the stationary axle with minimal friction.

Inside the bearing are precision-made rolling elements — normally balls on many motorcycle wheel applications — running between inner and outer races.

The bearing has to support loads while allowing thousands of rotations every mile.

A motorcycle normally has bearings on both sides of each wheel, together with internal spacers and other components that maintain the correct relationship between them.

Why Are Modern Bearings Sealed?

Many modern motorcycle wheel bearings are sealed and lubricated during manufacture.

The seals help keep grease inside while keeping water, dirt and other contamination out.

Unlike older serviceable bearing arrangements, a sealed bearing isn't normally dismantled periodically and packed with fresh grease.

When it becomes worn or damaged, it is generally replaced.

How Long Do Wheel Bearings Last?

There isn't a useful universal replacement mileage.

Bearing life depends on factors including:

• Mileage
• Road conditions
• Water exposure
• Pressure washing
• Wheel installation
• Bearing quality
• Correct spacers
• Motorcycle load
• Corrosion
• Previous bearing installation

A bearing can cover substantial mileage without trouble, while another may fail much earlier after water ingress or incorrect installation.

Condition is therefore more useful than mileage alone.

What Are the Symptoms of a Worn Wheel Bearing?

Possible symptoms include:

• Roughness when rotating the wheel
• Unusual rumbling or grinding noises
• Excessive play at the wheel
• Vibration
• Handling that feels unusual
• ABS problems on some motorcycles
• Visible corrosion or seal damage

These symptoms aren't exclusive to wheel bearings, so diagnosis still matters.

Tyres, brakes, steering-head bearings and suspension components can produce some surprisingly similar sensations.

Checking for Bearing Play

With the motorcycle safely supported and the relevant wheel unloaded, excessive movement may sometimes be detected by attempting to move the wheel laterally.

There shouldn't be obvious looseness attributable to the wheel bearings.

However, simply finding movement doesn't automatically identify the bearing as the source. Other components and mounting arrangements need to be considered.

Likewise, the absence of obvious play doesn't guarantee a bearing is perfect.

A bearing can become rough before substantial looseness develops.

Feel Matters

When a wheel is removed, the bearings can be assessed more directly.

Turning the inner race carefully by hand may reveal:

• Roughness
• Notchiness
• Binding
• Unusual resistance

A healthy bearing should generally rotate smoothly.

A bearing that feels rough when unloaded isn't likely to improve once it is supporting a motorcycle at road speed.

Water Is a Major Enemy

Wheel bearings live in an exposed environment.

Rain, road spray and washing all place water close to the bearing seals.

Once moisture reaches the internal bearing surfaces, corrosion can begin.

This is one reason aggressive pressure washing around wheel hubs and bearing seals isn't a particularly good idea.

A pressure washer can potentially force water past seals that cope perfectly well with ordinary road spray.

ABS Makes Bearing Identification More Important

On ABS-equipped Harley-Davidson® motorcycles, the wheel-speed sensing arrangement can make correct bearing selection and installation particularly important.

Some applications use a bearing incorporating a magnetic encoder associated with the ABS wheel-speed sensor.

The relevant side of the bearing must face the sensor.

Installing the wrong bearing — or installing an encoder bearing in the wrong orientation — can result in ABS faults even though the wheel itself rotates normally.

So when replacing bearings on an ABS-equipped motorcycle, don't assume that two bearings which appear similar are interchangeable in every position.

Don't Hammer a Bearing in Carelessly

Wheel bearings are precision components.

Installation technique matters.

Force should be applied to the appropriate bearing race for the particular installation operation.

Transmitting installation force through the balls can damage the bearing before the motorcycle has even left the workshop.

The fact that a newly installed bearing still turns doesn't prove that it hasn't been damaged.

Correct bearing drivers and procedures exist for a reason.

The Internal Spacer Matters

Between the wheel bearings is normally an internal spacer.

This isn't an optional tube included merely to stop things rattling around inside the hub.

It forms part of the wheel-bearing and axle assembly.

When the axle is tightened, the inner bearing races and spacer need to work together correctly.

A missing, damaged or incorrect spacer can place inappropriate loads on the bearings.

Whenever wheel-bearing problems occur repeatedly, checking the surrounding components makes sense.

Don't Forget External Spacers

External wheel spacers also need to return to their correct positions.

Mixing spacers, omitting one or installing components incorrectly can affect wheel alignment, brake alignment and bearing loading.

When removing a wheel, keeping track of which spacer belongs where can save considerable trouble during reassembly.

Should Both Bearings Be Replaced Together?

If one bearing has failed through age or general wear, replacing the other bearing in the same wheel is often sensible.

They have normally experienced similar mileage and environmental conditions.

The precise decision depends on the application and condition, but bearing replacement is one area where saving one apparently serviceable old bearing may not always represent much of a saving.

Cheap Bearings Can Be Expensive

Wheel bearings aren't components where unknown quality is particularly attractive.

A bearing failure can affect wheel control, brake alignment and potentially the ABS system.

Using a reputable bearing of the correct specification is considerably more important than finding the lowest possible purchase price.

Check Bearings During Tyre Changes

Tyre replacement provides an excellent opportunity to check wheel bearings.

The wheel is already removed, making it much easier to feel the bearings directly.

A few seconds checking for roughness can identify a developing problem before the wheel goes back into the motorcycle.

The Bottom Line

Wheel bearings are largely invisible when they're doing their job correctly.

That's exactly how they should be.

But they support the motorcycle, allow the wheels to rotate and influence both handling and braking.

Check them whenever the wheels are removed, pay attention to new noises or play and don't ignore roughness simply because the bearing hasn't covered a particular mileage.

And on ABS-equipped motorcycles, remember:

Correct bearing specification and correct orientation can be just as important as the bearing itself.

About Hogparts

Hogparts has specialised in parts, accessories and workshop support for Harley-Davidson® motorcycles for many years. Our Knowledge Centre provides practical information intended to help owners understand their motorcycles and make informed decisions about servicing, repairs and replacement parts.

Hogparts UK Ltd is an independent business and is not affiliated with, endorsed by or sponsored by Harley-Davidson Motor Company. Harley-Davidson® is a registered trademark of Harley-Davidson Motor Company.