02/08/2026 8:38 am
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Forester hum gets louder on left turns but the tires also show cupping
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A 2017 Forester has a 40–60 mph hum. It grows louder in a gentle left curve and quieter in a right curve, suggesting the right side, but both rear tires have light cupping. No bearing has measurable play on the lift.
How can tire noise be separated from a loaded wheel bearing without swapping parts?
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03/08/2026 7:51 am
Use chassis microphones at both rear knuckles and a reference point, then repeat the same road speed on straight, left-load and right-load sections. A bearing usually changes sharply with lateral load at one knuckle, while tread noise follows road surface and may remain more uniform. Rotating the tires front to rear is another controlled comparison if sizes permit.
Lift-spin tests can miss a bearing that is quiet without vehicle weight. Record the route and load direction so the result is repeatable.
Topic starter
04/08/2026 8:40 am
The right-rear knuckle channel increased by more than 10 dB during left loading while the tire reference barely changed. After right-rear bearing replacement, that channel and the cabin hum disappeared; the remaining light tread noise changed with pavement.