Inspect, Replace and Repack Wheel BearingsWhen the squeaky wheel really gets the grease
Every wheel on every vehicle spins around thanks to smaller wheel bearings. The bearings themselves contain rollers that spin around inside a cage to bear the load of the vehicle on the axles. The rollers are often tapered, or angled, against the cones in which they spin in order to handle the immense loads placed against the wheels when turning right or left. With proper care and lubrication, most wheel bearings should roll down the highway for over 100,000 miles with no complaints.
Bearing It All
When bearings do complain the noise is usually speed-specific-the noise varies according to the speed of the spinning wheel in which it is contained. Clicks, rumbles and groans that vary with vehicle speed may indicate a bearing that has lost its ability to handle the load. Another good way to check wheel bearings without disassembly is to jack the wheel in question up off the ground, grab it from both the top and the bottom, and attempt to move it. There should be very little or no movement at all.
Give Bearings a Brake
If your wheel bearings are A-OK, the best way to keep them that way is with regular lubrication. A sensible time to check and lubricate the wheel bearings is when brake service is performed, as removal of calipers and rotors will allow access to the wheel bearing. While some bearings are relatively easy to inspect and service, others are pressed onto axles, and even worse are the captured bearing type. Specialized tools and procedures make captured bearing service best left to the professional.
Too Much to Bear
Things to look for when inspecting wheel bearings are loose or broken tapered rollers, scored race or roller surfaces, or excessive play in the assembly. The shiny surface of a bearing is specially hardened and should be a uniform color. Hot spots, different color lines or scoring indicate wear through to the softer metal underneath. The worst-case scenario of bearing failure is excessive heat buildup. The friction created by the malfunctioning bearing can generate enough heat to shear an axle. A wheel bouncing down the road ahead of a vehicle is not a welcome sight.
The only difference between a bearing working for 100,000 miles or failing prematurely is quality high-temperature wheel-bearing grease. Since brakes convert vehicle inertia into heat as they slow the vehicle, the surrounding area can get extremely hot. Low temperature or chassis grease will liquefy and slip-up the brakes-not good. The other rule of grease is that grease types are not always compatible. Always re-lubricate with high-temperature wheel-bearing grease of the same type. To lube a bearing, use either a gob in the palm of your hand or a wheel bearing grease tool to pack the bearing. The key is to get grease inside all bearing surfaces.
When replacing bearings always replace everything. Bearings, seals, races and so on, must all be replaced as a matched set. A wheel bearing tool set makes seating in the races and seals a breeze while a solid drift works much better than a screwdriver for batting bearings out of the hub.
Over-tightening the axle nut is a common cause of bearing failure. Tighten the nut while spinning the rotor or hub, then loosen it, then use about half as much force as it took to tighten it again. If there is question, consult the service manual for the correct torque specifications-don't guess. Finally, always use a new cotter pin, as it is cheap insurance against wheels liberating themselves from the axles.
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