I have a this humming (low pitched) noise for a couple of weeks now but cannot find the problem. It sounds like loud tire noise and it happens around 40mph and disappears if I tap on the brakes. The sound intensifies a little when I turn the wheel left or right.

The noise is coming from the front so I don't think it's the rear u-joints. Could it be bad wheel bearings? I checked the driver side hub and the runout is within spec, also checked the front diff fluid level. How could you tell if there is a bad CV joint? Any help would be much appreciated.. Thanks.

Alex