2007-2015 Mazda CX-9 Hub & Bearing Failure: Diagnosing Noises and Replacement Differences

Symptoms of a Failing Hub Assembly or Wheel Bearing

A failing wheel bearing on a 2007-2015 Mazda CX-9 gives several distinct warning signs. The most common and noticeable symptom is a noise coming from one of the corners of the vehicle.

• Humming, Roaring, or Grinding Noise: This is the classic sign of a bad bearing. The noise sounds like a loud hum, a deep roar, or a metal-on-metal grinding. It typically starts faint and gets progressively louder over weeks or months. The sound is directly related to vehicle speed — the faster you go, the louder it gets.
• Noise Changes When Turning: This is a key diagnostic clue. If the noise gets louder when you steer to the right, the failing bearing is on the left side of the vehicle (as the turn puts more load on the outside wheels). Conversely, if the noise increases when turning left, the bad bearing is on the right side.
• Vibration in the Steering Wheel: A worn bearing can develop excessive play, causing vibrations that you can feel in the steering wheel. This vibration may be more noticeable at higher speeds or while turning.
• ABS or Traction Control Warning Light: The hub assembly contains the sensor ring that the ABS wheel speed sensor reads. If the bearing has excessive play or the sensor ring is damaged, it can cause an erratic signal, triggering the ABS and/or traction control warning lights on your dashboard.
• Vehicle Pulling to One Side: In severe cases, a very loose bearing can cause the wheel to wobble, making the vehicle pull to the side of the failed bearing.

Known Issues, Recalls, and TSBs

Wheel bearing failure is a widely reported issue for the first-generation (2007-2015) Mazda CX-9, with many owners in forums reporting failures well under 100,000 miles. Some owners believe the original parts were not robust enough for the vehicle's weight.

Front vs. Rear: A Critical Difference

It is extremely important to understand that the front and rear wheels on this vehicle use different systems:

• Front Wheels: Use a press-in wheel bearing. This is not a complete assembly. The bearing itself must be pressed out of the steering knuckle and a new one pressed in using a hydraulic shop press. The hub is a separate component that is also often replaced. This is a difficult and tool-intensive job.
• Rear Wheels: Use a complete, bolt-on wheel hub assembly. This unit contains the hub, bearing, and mounting flange all in one piece. It is unbolted from the suspension and replaced as a single unit, making it a much more straightforward repair for a DIY mechanic.

Important Safety Recall: Front Lower Ball Joints

While not a hub recall, there is a critical NHTSA recall (15V-385) for the 2007-2014 Mazda CX-9. Water can enter the front suspension's lower ball joints, causing rust and corrosion. This can lead to the ball joint separating from the lower control arm, resulting in a sudden and complete loss of steering control. If you are working on the front suspension to replace a wheel bearing, it is essential to check the status of this recall and inspect the ball joints carefully.

Buying a Used Hub Assembly

For the 2007-2015 Mazda CX-9, buying a used part is a viable option only for the rear wheels, as they use a complete bolt-on assembly. The front requires a new press-in bearing, so buying a used front steering knuckle with an old bearing still in it is not recommended.

When buying a used rear hub assembly:

• Inspect for Smoothness: The most important check is to spin the hub by hand. It should rotate smoothly and silently with no roughness, grinding, or catching. Any noise or gritty feeling means the bearing is already failing.
• Check for Play: Hold the hub flange and try to wiggle it side-to-side and up-and-down. There should be absolutely zero play or looseness. Any movement indicates a worn bearing.
• Mileage is Key: Since these bearings are a known wear item, prioritize parts from low-mileage vehicles. Aim for an assembly with under 75,000 miles if possible. A high-mileage used bearing may not last long.
• Visual Inspection: Look for signs of heavy rust, corrosion, or impact damage to the flange or housing. Ensure the wheel studs are straight and the threads are in good condition. Check that the ABS sensor cable (if attached) is not cut or damaged.
• Why Used OEM? A quality, low-mileage used OEM rear hub assembly can be a better value than a cheap, new aftermarket part. The original Mazda parts are built to a specific quality standard. Many low-cost aftermarket hubs use inferior bearings and seals that can fail prematurely.

Cost Breakdown

Prices can vary based on location, brand, and the specific part needed (front bearing vs. rear assembly). The costs below are estimates.

Replacement Procedure Overview

Replacing the rear hub assembly is a feasible DIY job for someone with mechanical experience and proper tools. Replacing the front press-in bearing is not recommended for DIYers without access to a hydraulic press and specialized bearing adapters.

Rear Hub Assembly (Bolt-on)

1. Safely raise and support the vehicle and remove the wheel.
2. Remove the brake caliper and caliper bracket, and hang them securely out of the way. Remove the brake rotor.
3. Remove the axle nut from the center of the hub.
4. From behind the knuckle, unbolt the 4 bolts holding the hub assembly in place.
5. Remove the old hub assembly. This may require some force if it is rusted in place.
6. Clean the mounting surface on the knuckle before installing the new hub.
7. Installation is the reverse of removal. Be sure to use a torque wrench for the hub bolts 🎬 See this walkthrough for replacing the rear bearing without removing control arms and the main axle nut.

Front Bearing (Press-in)

The general process involves disconnecting the tie rod, ball joint, and strut from the steering knuckle, removing the CV axle from the hub, and then removing the entire knuckle assembly from the vehicle. The assembly is then taken to a bench where a press is used to push the old hub out of the bearing, remove a snap ring, and then press the old bearing out of the knuckle. The new bearing is then pressed in, followed by the snap ring and the hub. This process requires precision to avoid damaging the new bearing or the knuckle.

Frequently Asked Questions