Trailer Bearings: How to Maintain, Lubricate, and Replace Them

What Are Trailer Bearings?

Trailer bearings are sets of steel balls or rollers housed in a race and packed with grease, situated at each wheel hub. Their job is to reduce friction between the rotating wheel hub and the stationary axle spindle. Without properly functioning bearings, metal-on-metal contact would lead to:

• Extreme heat
• Friction
• Component failure

Most trailers utilize tapered roller bearings, which handle both axial (side-to-side) and radial (up-and-down) loads effectively. These are commonly paired with bearing races pressed into the hub. The bearings themselves spin against these races with the help of grease to minimize heat and wear.

Why Maintenance Matters

Ignoring trailer bearing maintenance is like playing roulette with your load. Over time, grease breaks down, water seeps into the hub, and corrosion starts to develop. What follows is accelerated wear, excessive heat buildup, and potentially a seized wheel or separated hub.

Routine inspection and lubrication of trailer bearings not only extend bearing life but also protect your:

• Wheel hubs
• Spindles
• Brake components

Preventive care minimizes downtime, especially in fleet operations where one out-of-service trailer can cause logistical chaos.

Signs of Failing Trailer Bearings

Before you hit the point of no return, failing bearings will give you warning signs. Be on the lookout for:

• Excessive wheel play or wobble
• Grinding, rumbling, or squealing noises from the wheel hub
• Grease leakage around the wheel end
• Overheated hubs (burnt paint or smoke)
• Uneven brake wear due to compromised wheel alignment

Catch these early, and you’ll avoid a full-blown roadside failure.

How to Lubricate Trailer Bearings

Lubrication keeps trailer wheel bearings turning, and there are two main types used in the field: grease-packed bearings and oil-bath bearings.

Grease-Packed Bearings

Grease-packed bearings are the most common in light- and medium-duty trailers. Follow these steps to lubricate them correctly:

1. Remove the Hub – After safely lifting the trailer and removing the wheel, take off the dust cap, cotter pin, spindle nut, and washer. Slide the hub off the spindle carefully.
2. Clean the Bearings and Races – Use solvent to clean off all old grease and inspect the rollers and raceways for pitting or scoring.
3. Pack the Bearings – Using a bearing packer or your hand, force high-temp bearing grease into all gaps between the rollers.
4. Reassemble – Insert the packed bearing into the race, reinstall the hub, washer, and spindle nut. Tighten and then back off slightly to allow freewheel spin.
5. Install a New Cotter Pin and Cap – Never reuse old cotter pins. Always reseal with a clean dust cap.

Grease should be rated for high-temperature disc brake systems and resistant to water washout. A quality lithium-complex grease with an NLGI #2 rating is standard in the industry.

Oil-Bath Bearings

Heavier trailers—particularly those with air brakes and 10,000 lb.+ axles—may use oil-bath hubs. These are simpler to maintain but require more frequent inspection.

1. Check the Oil Level – Sight glasses or removable plugs make it easy to confirm the level.
2. Top Up with Gear Oil – Use SAE 90 or 80W-90 gear oil approved for axle lubrication.
3. Change When Cloudy or Milky – This is a sign of water contamination.

Maintenance Intervals

Industry best practices recommend inspecting and repacking grease-packed trailer bearings every 12,000 miles or 12 months, whichever comes first. However, for fleet trailers or those in extreme-use conditions, shortening that to every 6 months is advisable.

Oil-bath bearings should be checked before every long haul and fully drained and replaced every 50,000 miles or annually.

When performing BIT inspections in California, trailer bearings are among the wheel-end components visually inspected every 90 days. Neglected bearings are a frequent failure point during these mandated checks.

How to Replace Trailer Bearings

When replacement is the only option, follow this professional workflow:

1. Remove the Hub Assembly – Disassemble as if you’re repacking.
2. Punch Out the Old Races – Use a brass drift and hammer to tap them out from the opposite side.
3. Install New Races – Using a race driver or bearing installer, seat the new race flush with the hub bore.
4. Insert New Bearings – Always replace bearings as a matched set with the race.
5. Lubricate Thoroughly – Pack new bearings or fill the hub with oil as appropriate.
6. Reassemble and Torque to Spec – Improper torque leads to either bearing preload or excessive endplay.

Always match the bearing to the hub manufacturer's specifications. Never mix and match bearings of similar size but different tolerances.

Preventing Future Failures

Aside from scheduled maintenance, take these steps to extend the lifespan of your trailer wheel bearings:

• Avoid high-pressure water near the hubs during washing
• Use hubodometers for mileage tracking
• Install hub seals correctly to prevent water ingress
• Keep spare bearings, seals, and grease in your road kit

Above all, ensure your techs are trained in proper torqueing and inspection procedures. Loose wheel bearings don't just cost you money—they can cost you a DOT citation, failed BIT inspection, or worse, a load lost on the highway.

Stay Ahead With Bearing Care

From regular repacking to full-blown replacement, understanding the ins and outs of trailer bearings is essential for any fleet or operator. These small but critical components do the heavy lifting—literally—by keeping your wheels turning smoothly and safely. With proper maintenance, quality parts, and a bit of diligence, you’ll keep your trailers rolling and your operations on schedule.

If you require trailer preventive maintenance near Fontana, CA, reach out to JB Trailer Service today.