What part of your vehicle has little metal balls inside that are lubricated and allow you to cruise on down the road?  They are wheel bearings, and automotive designers might argue they are human beings' second greatest invention of all time (the first is, of course, the wheel!). You have a wheel bearing at each wheel.  They allow your wheels to turn freely, minimizing friction that would ordinarily slow you down when metal meets metal.  When one of your wheel bearings starts to go bad, it lets you know. A wheel bearing does its work quietly when it's in good health but starts getting noisy when it isn't.  People describe the noise differently.  Sometimes it sounds like road noise, a pulsating, rhythmic, sound.  That pulse speeds up when your vehicle speeds up.  Here's what's happening when you hear that sound.  As mentioned, the bearing has these little metal balls inside a ring.  They have a lubricant inside to reduce friction between the ... read more