Automobile wheels spin round thanks to the miracle of wheel bearings. The bearings themselves contain rollers that spin around inside a cage. Wheel bearings are often tapered against the coned races in which they spin in order to handle the lateral forces placed against the wheels when the vehicle turns. Given the right grease and care, most wheel bearings should roll without complaint for 100,000 miles or more. Neglected bearings will tell another tale.
Wheel bearings need grease like tires need air. A swell time to inspect and grease up the wheel bearings is when wrestling with brake pads or brake caliper removal. Halfway there is always a good reason to press on. While some bearings are relatively easy to inspect and service, others are pressed onto axles or worse - of the captured bearing variety. Specialized tools and procedures make captured bearing service best left to the professional. Front wheel bearings on rear-drive cars are fairly basic.
Whine and Grind
When bearings go bad the noise is usually speed specific - clicks, groans, rumbles and noise that varies according to the speed of the spinning wheel in which the bearing is contained. A quick 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. Lots of slop? Read on.
Reading bearings involves taking a look. Peer closely for loose or broken tapered rollers, scored race or roller surfaces, or excessive play in the assembly. The shiny surface of a bearing is hardened, and should be of a uniform color. Hot spots, different color lines or scoring indicate wear through to the softer metal underneath. Worst-case scenario? Friction created by a cooked bearing can generate enough heat to shear an axle. One of your own wheels bouncing down the road ahead of you is never a good thing.
Top quality high-temperature wheel bearing grease is the key to wheel bearing longevity. Brakes convert vehicle inertia into heat as they impart whoa. A lot of heat. Low temperature or chassis grease will liquefy and slip-up the brakes. The other rule of grease is that grease types are not always compatible. Out with the old and in with the new. Use solvent to remove grease and dirt from bearings. Let the wheel bearing air dry. Always relubricate with high temperature wheel bearing grease of the same type.
Replace wheel bearings, seals, races, and so on as a matched set. Bearing quality, as we recently discovered, makes a difference. Spending some extra money for good bearings now can save time later. A seal and race driver tool set makes seating in the races and seals a breeze. A solid drift works much better than a screwdriver for batting bearing races out of the hub. Always use a new cotter pin as a finishing touch. One penny is cheap insurance against wheels liberating themselves from axles.
Stuff You'll Need:
· Matched Set of Wheel Bearings and Seals
· Jack and Jack Stands
· Vehicle Service Manual
· Hand Tools
· Seal and Race Driver Set
· Wheel Bearing Grease
· Brake Cleaner, or similar
With wheel, and brake caliper removed use a screwdriver to gently pry the bearing grease cup away from the hub. A tap with a rubber mallet can help loosen things up. Turning the wheel a little each time helps get the job done. Never let brake calipers hang by the brake hoses. That's what bailing wire is for.
Remove the cotter pin, retaining ring, and axle spindle nut. Use the dust cap to keep all the parts together. Grab the disc and remove the hub or rotor-hub assembly from the axle. The outer wheel bearing will drop out.
Inspect bearings and races for scoring, flat spots, cracks or broken rollers. Also take a good look at the seal. If all is well then repack with grease and put it all back together. If not then bust out the new bearings and seals.
Use a drift and hammer to knock the outer race from the hub. Tap alternately on each side of the race to prevent cracking it. Flip over the hub and use the same procedure to knock out the inner race, bearing, and seal. A block of wood or old brake rotor can help.
Pack the new inner and outer wheel bearings by either pressing grease in by hand or using a fancy bearing packing tool and grease gun. The idea is to force the grease inside the cage and rollers.
Selecting the right size driver is the key to driving home the races and seals. Hammer time. Drive in the inner race. Make sure the race is seated all the way. Place bearing in race and pack in some grease. Use the tool again to seat the grease seal. Flip over the hub and repeat for the outer race. Seat the races and seals in level. Driving them in crooked will peg the swear-o-meter.
Pack in a good amount but do not completely fill inside the hub with grease. Place hub on spindle. Put the outer wheel bearing, washer, and axel nut back on. While spinning hub tighten axle nut enough to seat the whole assembly. Loosen the nut, then re-tighten by hand to specifications. Do not overtighten! Too much load will cook the bearings in short order.
Replace retaining ring and secure with new cotter pin. Never reuse cotter pins. Replace bearing grease cup being careful not to inflict too many bearing interfering dents. Clean all excess grease from outside of hub with brake cleaner - the stuff of miracles. Don't forget the calipers. With the wheel installed check for play.