Wheel Bearing Tech Tip

The two parts I hate about doing wheel bearings is getting the old grease out, and the new grease in.

To clean 'em, all you have to do us hit them with an air blow off gun, and blast it all right out. Gets all the major stuff between the rollers out real quick. Then a quick shot of brake cleaner, and they are clean as a whistle. Don't sit and spin the bearings in the inner race with air, though. They don't like that.

You might give the unenlightened a small tip about where the old grease goes when you "blast" it out. Like everywhere, unless you plan in advance.

To repack them, I found you can get a small syringe, and fill it with grease. (I like the HD stuff, but only because it's blue) The important part of packing bearings is to completely fill the cavity between the rollers with grease. With the syringe, it's a piece of cake. Just point it in the gap, and fill 'er up. Goes real quick. Once the gaps are filled, finish by smearing grease around the outside of the rollers.>

Personally, I prefer the Snap-On bearing packer, a plastic cylinder about 6 inches in diameter, and maybe 5 inches in height. It has an inverted conical piece inside, with holes, that rides on the grease reservoir. Put the bearing in, put the plastic pusher on top, and
lean on it. Presto! All cavities filled.

As far as grease goes, a long ago tech tip in a forgotten magazine recommended the molybdenum disulfide grease that VW used in their front wheel drive CV joints. I bought some. It was expensive. I used it only on my personal bikes for several years, with NO problems. When I went back to the VW dealer for a refill, the parts guy gave me the NAPA equivalent (much less money), and I have been using it ever since. No problems - zero.

After cleaning the hub races and coating them with grease, drop the rollers in and install the wheel seals. On my 16" front, the seal goes flush with the hub. The rear though, needs to be recessed about 1/4".

BEFORE putting the bearings back in, check the wheel bearing end play. Out of five tires I recently installed, the end play was non-existent on two of the wheels. I clean the bearings, then re-install them dry, with the tire/wheel assembly upright in my machinist's vice, and put the axle through with enough spacers to be able to torque the axle nut to
recommended value. Then I check wheel bearing end play with a dial indicator. Different years have different values, so check the manual for your model. Insufficient endplay will cause the bearings to overheat and in extreme cases, weld to the axle, with unpredictable and unpleasant results. Excessive end play will cause handling problems, and eventual
destruction of the bearings.

Then, and only then, do I grease and reassemble the bearings. When re-assembling, pay attention to the spacer between the inner bearing races. On most late model wheels, the basic spacer (looks like a piece of pipe) is brought into spec with shims. There is one standard shim with a raised lip. This lip must contact the inner race of the bearing. The final shimming is done by choosing the appropriate stack of shim washers, which come in thicknesses of .004, .008, .016, and .032 inch. These go between the basic spacer and the lipped spacer washer. I always put the thickest shim washer in contact with the basic spacer, and sandwich the thinner ones between it and the lipped spacer washer. Put a light film of grease on all the spacer stuff, to retard rust in case water seeps inside the bearing cavity.

Check your manual for specs on where oil seals should be seated. The important variable, I believe, has to do making sure that the seal is properly seated on the spacer. The seal should ride on the inner half of the spacer, but not so close to the bearing that the seal is on the chamfered edge of the axle spacer. Be sure the lip of the seal is lubricated before iinserting the spacer. Also, be sure that the spacer has no