Trailer bearings: when to grease, inspect and replace them

Short answer: according to Dexter's maintenance manual, a trailer's wheel bearings should be cleaned, inspected and repacked every 12 months or approximately every 19,000 km (12,000 miles in the manual, which is American), whichever comes first. They are replaced as soon as you see pitting, spalling or rust, and always as a pair: the cone with its cup (also called a race; in our catalogue, it is listed as the "cage"). The rest is a matter of how.

How often: what the manufacturer says

In its maintenance schedule for trailers and RVs, Dexter places these three items in the 12-month or approximately 19,000 km column:

• Bearings and cups: check for rust and wear, clean and repack.
• Seals: check for leaks, and replace the seal every time it has been removed.
• Hub and drum: check for abnormal wear or scoring.

Two situations change things. If you launch your boat trailer into the water, Dexter specifies that axles without E-Z Lube are not designed to be immersed: the bearings must be repacked after each immersion. Nev-R-Lube sealed bearings are not designed for immersion either. The E-Z Lube system is designed for immersion, but the grease fitting at the end of the spindle does not replace periodic bearing inspection. And if your axle comes from another manufacturer, that manufacturer's manual has the final word.

How to inspect a trailer bearing

Here are the main steps from the Dexter manual for a standard grease-lubricated axle:

1. Raise and support the trailer according to the manufacturer's instructions, then remove the wheel.
2. Remove the grease cap by prying it up gradually all around the flange.
3. Remove the cotter pin, unscrew the spindle nut and remove the washer.
4. Pull the hub off the spindle without dropping the outer bearing.
5. Remove the seal with a seal tool or a screwdriver. Dexter is clear: never push the seal out by striking the inner bearing, as this can damage it.

Next, clean the cone with solvent, dry it with a lint-free cloth and examine each roller one by one. A tip from the manual that saves bearings: never spin them with compressed air.

Take the opportunity to inspect the drum. According to Dexter, if scoring or wear exceeds 0.090 in on the diameter, the drum must be replaced. Below that, if it is more than 0.020 in oversize or 0.015 in out of round, it must be machined.

Repacking and reassembly

Repacking by hand, with a tool or through the grease fitting

The manual's method is simple. Place a ball of grease roughly the size of a toonie ($2 coin) in the palm of your hand. Press the large end of the bearing into the edge of the grease to force it between the rollers, then rotate the bearing from one roller to the next until it is full. Before reassembly, apply a thin coat of grease to the cup.

If you have four or six wheels to do, a bearing packer such as the Lisle Handy Packer speeds up the work and keeps the grease where it belongs.

As for grease, Dexter publishes a list of approved products (for example, Shell Gadus S3 V220C or Mobilith AW 2) and warns against mixing lithium, calcium, sodium or barium complex greases. If you switch to a different type of grease, remove all of the old grease first.

E-Z Lube axle. Remove the rubber plug from the grease cap and attach a manual grease gun to the fitting at the end of the spindle. Do not use a pneumatic grease gun: according to Dexter, it pushes the grease in too quickly and can force it past the seal. Rotate the hub while pumping slowly, and stop when clean grease starts to come out. Wipe off the excess and replace the plug.

Oil-filled hub. Check the level in the clear cap and top up as needed with SAE 90, 80W-90 or 75W-90 hypoid gear oil, up to the level marked on the cap.

Reassembly and end play adjustment

To replace a cup, Dexter drives it out and then back in by tapping with a brass drift, until it is seated firmly against the hub shoulder. Never strike the new seal directly, and it does not need to be driven all the way to the bottom.

For a standard axle with a cotter pin, the adjustment is done as follows:

1. Rotate the hub slowly while tightening the spindle nut to approximately 50 lb-ft.
2. Loosen the nut to remove the torque, without rotating the hub.
3. Retighten by hand, just enough for it to be snug.
4. Back off the nut to the first slot that lines up with the cotter pin hole, then insert the pin and bend its legs.

The expected result: the nut is free to move slightly and is held only by the cotter pin. Axles with a nut retainer use a slightly different procedure, so follow the manufacturer's instructions for your model.

When to replace rather than repack

The Dexter manual leaves little room for interpretation:

• Pitting, spalling or rust on the bearing: replace it.
• Always as a set: a new cone goes with a new cup. Our trailer bearing kits are made for this, and individual parts are in the trailer bearings collection.
• Nicked or torn seal, or the slightest doubt: replace it. See our trailer seals.
• Drum scored beyond 0.090 in on the diameter: replace it. You will find these under hubs and drums.
• Nev-R-Lube bearings: Dexter calls for inspecting them every year or approximately every 19,000 km. Excessive end play, a wheel that binds, noise or a rough rotation, and the unit is replaced.

Our recommendations

• Choose a fixed time of year, for example before putting the trailer into storage, so the 12 months do not slip by.
• Have a new seal on hand before opening the hub, since Dexter calls for replacing it every time it is removed.
• Write down the numbers stamped on your bearings and seal. It is the most reliable way to order the right part.

Have a question about the part that fits your axle? Contact our customer service team with your part numbers.