* Weight Transfer: When making a left turn, weight shifts to the right side of the car. This reduces the load on the already potentially failing right front wheel bearing, lessening the humming sound or even silencing it temporarily. The increased load on the left side during the turn doesn't usually produce a noticeable change in sound because a failing bearing is generally asymmetrical in its degradation.
* Bearing Failure: Wheel bearings are designed to allow the wheel to rotate smoothly. A worn or damaged bearing creates friction, generating the humming sound. The sound often increases with speed.
Other less likely possibilities include:
* Tire Problems: Although less likely to be affected by turning, a slightly out-of-balance tire or a tire with a developing defect *could* create a humming sound. However, these usually don't disappear with a left turn.
* Driveshaft Issues: While less common, a problem with the driveshaft could cause humming. But the correlation with left turns makes a wheel bearing much more probable.
In short: The change in the noise during a left turn strongly suggests a failing right front wheel bearing. It's crucial to have this checked by a mechanic as soon as possible. Driving with a severely worn wheel bearing is dangerous as it could lead to a complete bearing failure, causing loss of wheel control.
