This article breaks down the most effective ways to diagnose and address common Subaru Forester wheel bearing issues. It’s a practical guide based on years of working on these cars, moving beyond simple replacements to help you understand the root causes of the problem and prevent future failures.
The Subaru Forester, known for its reliability and off-road capabilities, can sometimes suffer from wheel bearing issues. These problems usually manifest as a humming, grinding, or clicking noise that increases with speed. Ignoring these noises can lead to further damage and potentially dangerous driving conditions. A failing wheel bearing can cause excessive heat buildup, damage the hub, and even lead to wheel separation in extreme cases.
Identifying the Source of the Noise
Pinpointing which wheel bearing is failing can be tricky. The noise often seems to emanate from one area, but is actually traveling from another. A simple test involves listening closely while driving at moderate speeds (around 30-40 mph) and lightly swerving left and right. The side where the noise increases during the turn is typically the side with the failing wheel bearing.
Common Causes of Wheel Bearing Failure
Several factors contribute to premature wheel bearing failure in Subaru Foresters:
- Impact Damage: Hitting potholes or curbs can deliver a sharp shock to the wheel bearing, causing internal damage.
- Water Ingress: Damaged seals allow water and contaminants to enter the bearing, leading to corrosion and premature wear. This is especially prevalent in areas with harsh winters where road salt is used.
- Over-Tightening: Improper torquing of the wheel bearing nut can put undue stress on the bearing, shortening its lifespan.
- Poor Quality Parts: Opting for cheaper, aftermarket wheel bearings can often result in early failure.
- Suspension Issues: Worn or damaged suspension components can put extra stress on the wheel bearings.
Replacing a wheel bearing is relatively straightforward, but misdiagnosing the issue can lead to wasted time and money. Don’t immediately assume the wheel bearing is the problem. Other components can mimic similar symptoms.
Beyond the Obvious: Ruling Out Other Culprits
Before condemning the wheel bearing, inspect the following:
- Tires: Uneven tire wear, particularly cupping or scalloping, can generate noise similar to a bad wheel bearing. Rotate your tires to see if the noise changes or disappears.
- Brakes: Worn brake pads or rotors, especially if warped, can cause vibrations and noise that could be mistaken for a wheel bearing issue. Inspect your brake components and ensure they are in good condition.
- CV Joints: Clicking noises, particularly during turns, are more indicative of a failing CV joint than a wheel bearing. A torn CV boot is a telltale sign.
- Differential: A failing differential can produce a low-frequency hum or whine that resonates through the chassis, sometimes mistaken for a wheel bearing.
- Exhaust system: a loose heat shield can also create rattling noise.
Leveraging Technology: Using a Chassis Ear
A chassis ear, a diagnostic tool with multiple microphones that attach to various points on the vehicle, can be invaluable for pinpointing the precise location of a noise. Connect the microphones near each wheel hub, and then drive the vehicle while listening through the headset. The microphone closest to the failing wheel bearing will transmit the loudest and clearest sound. This tool eliminates much of the guesswork involved in diagnosing wheel bearing problems.
Not all wheel bearings are created equal. Opting for a cheap, aftermarket option might save money initially, but could lead to premature failure and repeat repairs.
OEM vs. Aftermarket: A Real-World Perspective
While OEM (Original Equipment Manufacturer) parts are generally considered the gold standard, reputable aftermarket brands can offer a good balance of quality and affordability. However, it’s crucial to research and choose brands known for their durability and reliability.
- OEM (Subaru): Guaranteed fit and performance. The most expensive option, but provides peace of mind.
- SKF: A well-respected Swedish manufacturer known for high-quality bearings.
- Timken: A reputable American brand with a long history of producing reliable bearings.
- NSK: A Japanese manufacturer that supplies bearings to many automotive manufacturers, including Subaru.
The Importance of Proper Installation
Even the highest-quality wheel bearing will fail prematurely if not installed correctly. Using a hydraulic press to install the bearing is highly recommended to avoid damaging the new bearing during installation. Ensure the hub and knuckle are clean and free of corrosion before pressing in the new bearing. Use anti-seize compound on the mating surfaces to prevent future corrosion.
Prevention is always better than cure. Adopting proactive maintenance practices can significantly extend the lifespan of your wheel bearings.
Protecting Your Investment: Practical Tips
- Avoid Potholes: While unavoidable in some areas, actively try to avoid hitting potholes and other road hazards.
- Proper Wheel Alignment: Regular wheel alignments ensure even tire wear and reduce stress on the wheel bearings.
- Regular Inspections: During routine maintenance, visually inspect the wheel bearings for any signs of grease leakage or play.
- Torque Wheel Nuts Correctly: Always use a torque wrench to tighten wheel nuts to the manufacturer’s specifications. Overtightening can damage the wheel bearings and rotors. The proper torque specification for a Subaru Forester wheel nut is typically around 89 ft-lbs (120 Nm), but always consult your owner’s manual or a reliable repair source for the exact value for your specific model year.
- Apply Undercoating: Consider applying an undercoating to your Forester, especially if you live in an area with harsh winters and salted roads. This will help protect the wheel bearings and other undercarriage components from corrosion.
Addressing Suspension Issues Promptly
Worn suspension components, such as struts, shocks, and ball joints, can put extra stress on the wheel bearings. Addressing these issues promptly will not only improve your vehicle’s handling but also extend the life of your wheel bearings.
Subaru’s symmetrical all-wheel-drive (AWD) system, while renowned for its capability, also plays a role in wheel bearing wear. The constant engagement of all four wheels places additional stress on the wheel bearings compared to a two-wheel-drive vehicle.
The AWD Factor: Unique Considerations
- Matching Tire Sizes: Maintaining consistent tire sizes on all four wheels is crucial for the proper functioning of the AWD system. Mismatched tire sizes can cause the differentials to work harder, leading to increased wear on the wheel bearings.
- Regular Differential Service: Regularly servicing the front and rear differentials with the correct fluid is essential for maintaining the health of the AWD system. Neglecting differential service can lead to increased friction and heat, which can indirectly affect the wheel bearings.
- Consistent Driving Habits: While Foresters are built for adventure, avoiding excessive off-roading or aggressive driving can minimize stress on the AWD system and wheel bearings.
- Electronic Stability Control (ESC) System: Modern Foresters come equipped with ESC. While helpful, excessive activation of ESC during driving can place increased stress on wheel bearings. Be aware of the driving conditions and adjust your driving accordingly.
| Symptom | Possible Cause | Action |
|---|---|---|
| Humming noise increasing with speed | Failing wheel bearing | Diagnose with chassis ear; replace faulty bearing |
| Clicking noise during turns | Failing CV joint | Inspect CV boot; replace CV joint if damaged |
| Vibration at highway speeds | Uneven tire wear, unbalanced tires | Rotate/balance tires; replace tires if worn |
| Grinding noise during braking | Worn brake pads or rotors | Inspect brake components; replace as needed |
| Noise changes during swerving | Failing wheel bearing | Confirm diagnosis with chassis ear; replace faulty bearing |
Addressing Subaru Forester wheel bearing issues effectively requires a combination of accurate diagnosis, quality parts, proper installation, and preventative maintenance. By following these steps, you can keep your Forester running smoothly and avoid costly repairs down the road. Remember that a noisy wheel bearing can indicate a serious problem, and addressing it promptly is essential for your safety and the longevity of your vehicle.
Here are some frequently asked questions about Subaru Forester wheel bearings:
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