If there’s one thing every truck owner should know about wheel-end maintenance it’s that bearing adjustment, lubrication, and seal installation require a level of precision and consistency you just can’t achieve with a hammer.
Proper wheel-end-play is between one- and 10-thousandths of an inch, so there’s not much room for sloppiness. To complicate things, every bearing, seal, or axle manufacturer seems to have its own particular ideas on how to set pre-load and what the torque values should be.
The way to be accurate is to measure end-play with a dial indicator, a time-consuming process.
One of the great recent innovations in truck equipment is the integration of the hub, bearings, seals, lubricant, spindle nut, and hubcap into one tidy package. The bearings can either be integrated into the hub or pressed in as a separate cartridge. The manufacturer sets the bearing adjustment during the assembly process, and the nut acts to retain it on the spindle. The unit is sealed up, with the right amount of lubricant inside, and there’s no need for any regular maintenance.
It’s a similar story with pre-adjusted wheel-end systems. Unlike a unitized wheel-end assembly, a pre-adjusted wheel end has a spacer between the inner and outer bearings. You can still perform adjustments: in fact, you can convert a spacer-adjusted hub to a traditional assembly by removing the spacer.
Like so many long-life components designed for heavy trucks and trailers, ‘low maintenance’ does not mean ‘maintenance free’. You and your drivers should know how to recognize the signs and symptoms of wheel-end trouble. Without the right amount of lubricant, bearings can overheat and become damaged, possibly leading to wheel separation.
Furthermore, your tractor may be decked out with low-maintenance hubs, but you never know what your drivers are going to hook up to. Trailers have a longer service life and yet are often maintained less consistently because of their nomadic existence.
At your next driver meeting, invite your maintenance supervisor to talk about how to recognize potential wheel-end trouble. Here are some topics to consider:
VISUAL CUES. Telltale signs of bearing damage include a discoloured hubcap sight glass, low oil level in the sight glass, or lubricant on the wheel, hub or tire. Check, too, for abnormal or uneven tire wear, as well as rust on the outer end of the axle spindle, on the bearing-adjustment nuts, and even on the outer bearing itself.
HEAT. One sign of defective bearings-heat-may appear only after covering some distance on the road. A burnt smell emanating from a wheel, smoke coming from inside the wheel, and water that evaporates quickly from the surface of a wet hub are all signs that the wheel bearings may be running hotter than normal.
If you can feel the heat just by approaching the hub, stay back and wait until it cools enough for a closer examination. The heat from the wheel could cause the air pressure inside the tires to increase-an unsafe situation.
DIRT AND WATER. Water can infiltrate the hubcap, contaminating the lubricant, which can cause the seal to wear prematurely.
The pressure washer is one culprit-the hubcap is not for target practice. But also consider what happens when the wheel end is submersed in a puddle in a loading area, for example. A slit in the hubcap normally acts as a breather vent for the heat and pressure that build up while the trailer is on the road. If the hub cools quickly when the hot wheel end is submersed, the dirty water can be sucked into the axle hub, contaminating the lubricant.
HANDLING. Talk to your drivers about how their vehicle is performing on the road, paying close attention to wheel vibration or noise, a “pulling” feeling during braking, and decreasing braking power.
PUT POLICIES IN PLACE. Perhaps the most important step in preventive maintenance involves writing down rigorous inspection and maintenance guidelines, drawing on your component supplier reps as resources. They see what’s going on in the field and are well armed with training and spec’ing ideas. Consider their expertise as part of the package.
Because the consequences of a lost wheel can be catastrophic, you’d rather have your driver or mechanic spot a little lubricant on a tire and call the vehicle in for a closer look than for that telltale sign to be greased-over brake linings and a gaping hole where the wheel assembly used to be.
Now that’s a point worth hammering home.
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