Get your bearings straight

A common concern people often ask technicians about is one of a howling noise related to the rotational speed of the wheels. Besides a tire problem, the effects of a worn hub bearing can result in more than just a squeaky wheel needing grease.

The job of automotive axle bearings is to carry the weight of the vehicle and transfer it to the wheels while they rotate. They are what provide the virtually frictionless rotation of the wheels that helps your car to continue rolling with minimal effort.

Similar to other mechanical devices, cars have an array of bearings in all sorts of areas to provide ease of movement between mechanical parts. Ball bearings are the most common, and the ones used in wheel hub assemblies are of the "Tapered Roller" type.

Regardless of the name and design, bearings do wear over time and need replacement. The first indicator of this is noise that can result in a howl, squeal, or groan. The sound is hard to ignore - if you've ever experienced wheel-bearing failure, then you'll know what we mean.

In earlier designs, the bearing assembly was in two pieces, one on the hub spindle and the other within the drum or rotor of the brake assembly. On modern cars the bearing is an independent assembly bolted to the wheel spindle or axle.

These modern designs last longer, require less maintenance, and are easy to service compared to earlier designs. The replacement interval is roughly at 150,000 km, and requires about an hour's-worth of labour.

To determine if wheel noise is in fact the bearings, a common check is to drive at a steady speed to the point where the noise is heard. Manoeuvre the steering wheel slightly and enough to sway the weight of the vehicle from side-to-side.  If the pitch of the noise changes then the bearings should be inspected.

Current day vehicles use bearing assemblies that look similar in design at all four wheels and seem interchangeable. You should only select replacements that meet or exceed manufactures specifications and are exact in design, size, and mounting configuration.

It's a good practice to have the bearings inspected while the wheels are off the car. Technicians typically look for excessive play, inspect the condition, and apply new grease where provision allows. You should consider using a synthetic type of grease to get the most life out of new wheel bearings.