Mutodi Ramulondo drives a 2000 VW Chico, which makes a high pitched whistling sound at higher speeds. He replaced the wheel bearings but a month later, the noise was back. He reached out to us for help.

Is it definitely a wheel bearing?

I think the first question to consider is, is the offending part definitely the wheel bearing? Could there be other wheel-end damage that could perhaps be the culprit? Perhaps a bad tyre? A worn hub? Dry Joints Or a misbehaving caliper?

Before we look at this specific case, let us discuss talk about wheel bearings and noises in general. The signs of a worn wheel hub bearing vary in severity. Some signs are difficult to detect, which leads to damage before corrective action can be taken. The timeframe in which damage occurs is based on driving conditions and/or the mechanical practices that were followed at installation.

Noise is a classic sign of a bad wheel bearing or wheel hub bearing. Here are some indicators of a worn wheel hub bearing or other wheel-end damage. Note that many of the symptoms below refer only to the front wheel bearings:

• Snapping, clicking or popping.

This can indicate a worn or damaged outer CV-joint. However, it also can be related to excessive bearing endplay, usually associated with inadequate clamping. This noise is typically heard when cornering or making sharp turns.

• Grinding when the vehicle is in motion.

Typically, this means there is mechanical damage in a wheel-end system. Related to a bearing, it means a loss of integrity such as roller or raceway damage. The noise is normally heard when turning or when there is a shift in load.

• Knocking or clunking.

This can signal excessive play in the CV-joints or U-joints. It also can be caused by excessive backlash in the differential gears. This is not generally associated with bearings and is normally heard either when shifting from changing directions, such as from forward to reverse or transitioning from accelerating to coasting.

• Humming, rumbling or growling.

These noises are normally associated with tyre, electrical or drivetrain components. If bearing-related, the noise or vibration is present when driving in a straight line, but intensifies when turning the steering wheel slightly to the left or right. Typically, the side opposite the rumbling is the defective side.

• Wheel vibration and/or wobble.

This is generally associated with a damaged or worn tyre, wheel or suspension component or severe chassis misalignment. When related to the hub or bearing, this normally indicates the loss of clamp or a bearing with extreme mechanical damage. It also can occur when lug nuts are not properly torqued.

• Shudder, shimmy or vibration at a constant speed.

This is normally associated with worn or damaged suspension components or tyres that are out-of-balance or out-of-round. It is not normally indicative of hub or bearing damage.

• Abnormal side pull when brakes are applied.

This is normally indicative of a defective caliper or equalizer, but it also can be a sign of worn brakes or rotors. However, severe looseness related to a bearing can also cause excessive runout, which may cause the brakes to pulsate or pull. The most common cause is a warped brake disc due to the caliper not retracting.

• Uneven disc or brake pad wear.

This is normally indicative of a bad caliper and/or a bad equalizer, which is not bearing-related. Severe looseness related to a worn or damaged bearing can cause excessive runout, which can cause uneven wear on the brake pads and/or rotor. The most common cause is a warped rotor due to the caliper not retracting.

• Abnormal or uneven tyre wear.

There are many causes of abnormal tyre wear. The most common are worn or damaged suspension components, misalignment, improper inflation or tyre selection. While extreme bearing wear or looseness can cause abnormal tyre wear, it is typically related to other failure modes.

• ABS failure, which could be internal or external to the bearing or hub bearing assembly.

In extreme cases, internal and external sensors can be damaged from excessive movement caused by too much end-play. This indicates a lack or loss of bearing clamp. This normally results from severe mechanical break up or damage. (Additionally, in designs where the sensor is mounted externally, sensor damage can result from corrosion, stones and other hazards.)

If it is definitely the wheel bearing, what could cause it to fail?

Of course, we can not pinpoint the exact issue without inspecting and driving the vehicle. However, here are some pointers as to the main reasons that a wheel bearing could fail:

• Faulty installation – inappropriate tools such as a hammer or an impact wrench can cause damage to the exterior and or interior of the wheel end bearing causing the wheel bearing to fail prematurely. If the bearing was hammered in rather than pressed in, it can easily become damaged. Also, re-using the old accessories such as bolts, nuts, circlips, split pins, seals,… instead of replacing them with new ones can cause the wheel end bearing to operate under abnormal or unsafe conditions, increasing wheel end bearing wear and risk of a car accident. 
• Insufficient or Incorrect Grease - You'd be surprised at just how many parts of your car need to be greased in order to operate smoothly and stay free of corrosion. Wheel bearings, chassis joints, ball joints and universal joints all need the right specification of grease. I recommend only using Castrol Wheel Bearing Grease.
• Impact damage or poor road quality – all impacts from driving through a pothole, driving over speed bumps or hitting the curb stone can damage a wheel bearing and reduce its lifespan.
• Poor quality wheel bearing – a wheel bearing is continuously under enormous pressure. Wheel bearings constructed of low-quality materials can have poor heat-treatment, resulting in premature wear and failure. Not every aftermarket spare part is of the same quality. Rather pay a bit more for a higher quality known brand.
• Driving conditions – driving through deep water or mud can cause your wheel bearings to fail. Water, mud or other contaminants such as dust or road salt could get past the seals and enter the bearing, polluting the grease and wearing away the bearings.
• Car modifications – fitting bigger or wider rims, tyres with lower thread walls, stiffer shock absorbers and suspension springs cause higher loads on the wheel bearing and can accelerate wear. Stick to rims, tyres, shock absorbers and springs that are specified by the car manufacturer to minimize the impact on the longevity of the wheel bearings.

Next steps…

Sometimes you can get by with a part on your car being in semi-good condition. That is not the case with wheel bearings. They are responsible for supporting the weight of your car and helping to move the wheels smoothly and easily. With that said they need to be high quality, and in excellent shape in order to perform properly.

• Have your bearings inspected: For a wheel bearing to be considered in perfect working order it must be clean, without any debris, and the seals must be intact and working well. If you’re unsure what kind of condition yours are in, you can have them inspected by a professional mechanic.
• If the seals starts to break down, replace them: In ideal circumstances the wheel bearings are meant to last for about 150 000kms, but that is not a set number. Rear bearings can be cleaned periodically to help prolong their lifespan. As soon as the seal begins to break down, it’s best to get them replaced immediately.
• Check your owner’s manual: Refer to your owner’s manual when replacing your wheel bearings. The parts required will be based on your make, model, and year. This is usually information you can find on your own.

Start My Car supplies top-quality SKF wheel bearings. Reach out to us and we can assist you in finding the correct part for your vehicle. Also, have the repairs carried out in a reputable workshop which have the correct tools and presses for the job.