You’d be hard-pressed to find a free-spinning wheel loaded to withstand any magnitude of a load that doesn’t use a greasable taper roller bearing. They can be found on trailers, the front wheels of vehicles, and the non-drive wheels of farm equipment.
Tapered roller bearings excel in applications where radial and thrust forces are high. They are generally used in pairs (inner and outer bearings on a wheel) to cope with axial forces. They also transfer load more evenly across the surface of the roll.
In 1895, farmer John Lincoln Scott of Wilmot, Indiana, received a patent for the roller bearing and a few years later Henry Timken invented the taper design. The roller bearing was born from the ingenuity of American farmers!
Tapered roller bearings, if maintained properly, will provide excellent service and a long life, often exceeding the machine to which they are attached. The following tips are all you need to keep riding!
The keys to long life of wheel bearings are cleanliness, grease and preload. These three areas are intrinsically linked but must be considered separately.
It is not uncommon to see a trailer or railcar with the bearing grease plug missing or damaged. The grease cap serves both to keep dirt and moisture from the bearing from accelerating wear and to prevent any grease that might liquefy due to heat from escaping.
If the grease softens, it will be stored in the cap with the potential to flow back into the rollers as it solidifies and the wheel is set in motion. The grease plug should be snug, seated against the hub and be of good integrity.
Wheel bearings need to be serviced. This involves being removed, chemically cleaned, and left to dry naturally. The roller, cage, bushings, and bushing should be carefully examined for wear, pitting, or discoloration, then repackaged with the appropriate grease.
The fastest and easiest way to grease a wheel bearing is to use a bearing lining tool. This device works by hand or by air pressure to force grease into the cavities between the rollers, cage, and inner and outer rings. When packaged properly, grease is forced out between the rollers and the cage and extruded from the side where the rollers meet the inner and outer rings.
what type of fat do you use?
It is also essential to use the correct grease on a tapered bearing. For this reason, I don’t like grease gun fed bearing packers. Most grease cartridges contain universal grease which lacks the chemical properties required for a wheel bearing traveling at 75 mph on the road for miles.
In addition, some manufacturers require a specific grease for wheel bearings. I know Ford and many other brands require a unique formulation. Each type of wheel bearing grease usually has a different color. There are black greases, red greases, traditional honey-colored wheel bearing greases, and maybe a few others.
Fats of different composition should never be mixed.
The area where most bearing maintenance is insufficient is setting the proper preload on the bearing. This chore is essential. If you over tighten the bearing, you will force it into the race due to the taper of the rollers. If the bearing preload is insufficient, the wheel will move on the spindle and the load on the rollers will not be uniform.
To check for excessive play (insufficient preload), lift the wheel in question and grasp the tire with one hand at the top and the other at the bottom of the tire (12 o’clock and 6 o’clock positions).
Push the top away from you, then pull the bottom of the tire back and forth towards you. If you feel movement, then the bearing preload is the cause and is insufficient. I like to do this whenever I have a wheel off the ground just to confirm that everything is fine.
Follow these steps to set the preload.
Install the fully greased inner and outer bearings.
Securely tighten the adjusting nut while turning the wheel or hub 10 full turns. It’s about putting the bearing in position and letting the grease find its place.
Loosen the nut just enough to remove all the preload. It will now be just a little hand tight. While turning the wheel, tighten the preload adjuster of a castle nut. Spin the wheel a few more times and check for free play. If there is, tighten slightly with the nut and recheck. If all is well, install the jam nut and cotter pin with the grease plug, and you’re done.
If a wheel bearing needs to be replaced, you should also install the new race that comes with it. The old one will be worn according to the wear pattern of the failed bearing.