How do you grease trailer bearings without nipples?

Properly lubricating trailer wheel bearings is essential for safe towing and preventing premature wear, but not all trailers have grease fittings or “zerks” on the hubs to allow easy access for greasing. So how do you get grease into sealed bearings or hubs without nipples? There are a few methods that can be used to effectively repack trailer bearings without grease zerks.

Why Proper Lubrication is Critical

Wheel bearings support the weight of the trailer and allow the wheels to spin freely. Without proper lubrication, the steel rollers and races inside the bearings would quickly overheat from friction and wear out. This can lead to seizures, lock-ups and potentially dangerous situations on the road.

Bearing grease serves several important functions:

• Reduces friction and heat
• Cushions impacts on bearings
• Seals out contaminants like dirt and moisture
• Prevents corrosion inside the bearing

This is why repacking the bearings with fresh grease at regular intervals is so critical. For boat trailers that are frequently submerged and other heavy-use applications, annual bearing servicing is highly recommended.

Options for Greasing Sealed Bearings

Many small utility trailers and newer models often have no grease fittings for periodic lubrication. Instead, they use pre-lubricated sealed bearings that are designed to last several years before needing replacement. But there are still a couple methods that can be used to repack the grease when needed:

1. Packing Through the Seals

This method involves carefully working grease down into the bearing cavity around the rollers through the rubber seals, usually with a needle nozzle grease gun. The key steps include:

1. Remove the wheel and hub cap to access the inner and outer sealed bearings.
2. Thoroughly clean the wheel hub and bearings to remove all old grease and contamination.
3. Carefully insert the grease nozzle through the rubber seal lip and pump small amounts of grease in multiple points around the bearing.
4. Rotate the hub periodically to work the new grease down into the rollers. Add more grease until it purges out the seals.
5. Reinstall bearings and replace the hub cap.

The seals are flexible enough to allow grease injection without damaging the seals if done carefully. This can effectively repack the cavities without fully disassembling the bearings.

2. Complete Bearing Replacement

For a more thorough lubrication, the sealed bearings can be fully removed to pack the new grease before reinstalling them. This involves a more extensive teardown:

1. Detach the hub assembly from the axle and remove the outer bearing.
2. Extract the inner bearing and thoroughly clean all parts.
3. Pack the cavities between both inner and outer bearings rollers with fresh grease.
4. Reinstall the lubricated bearing units with new seals.
5. Replace the hub, adjusting the bearing preload.

While more labor intensive, this fully exposes the bearing internals to ensure contaminants are removed and fresh grease coats all surfaces. It provides the most complete lubrication possible.

Selecting the Proper Grease

For effective lubrication, always use a high quality grease designed specifically for trailer wheel bearing applications. Look for a NLGI #2 lithium complex, moly-fortified grease. Key properties to look for include:

• High drop point – Minimum 500°F to withstand high temperatures in the hub.
• Water resistance – Prevents washout in wet conditions.
• Corrosion inhibitors – Protects against rust and oxidation.
• EP additives – Withstands heavy loads and shock loading.

Low quality general purpose greases may lack the required additives for bearing protection. It is also critical to keep grease free of dirt and contamination during the packing process.

Knowing When to Repack Trailer Bearings

For trailers with visible hubs, a visual inspection can determine if the grease appears contaminated. Any signs of rust staining, milky appearance or overheating indicates deteriorated grease that warrants repacking. Always repack after submersion in water.

For enclosed hubs, experts recommend repacking at these intervals as routine preventive maintenance:

• Small utility trailers – Every 2-3 years
• Boat trailers – Annually before boating season
• Travel campers – Annually before camping season
• Heavy-use horse/cargo – Every 6 months minimum

Repacking more frequently ensures fresh grease and is cheap insurance against bearing failure on the road.

Greasing Methods for Trailers With Nipples

For trailers equipped with grease zerks in the hubs, lubrication is more straightforward. Some key tips include:

Use a Grease Gun

Use a standard grease gun with the appropriate needle fitting to pump in new grease. Match the tip to the zerk fitting size or install an adapter.

Clean Before Greasing

Wipe any dirt and debris from the zerk fitting before attaching the grease gun. Debris injected into the bearing can cause rapid wear.

Prime the Gun

Pump the grease gun several times to prime it and ensure fresh grease with no air pockets is delivered into the bearing.

Pack Slowly From Both Sides

Pump 2-3 ounces of grease slowly into each zerk on both the inner and outer bearings. Go slowly to allow grease to penetrate without blowing out seals.

Rotate the Wheel

Rotate the wheel a quarter turn between pumps to help distribute the grease throughout the bearing.

Refill the Cavity

New grease will purge out old contaminated grease. Keep pumping fresh grease until clean grease without bubbles appears.

Follow your trailer manufacturer’s specs for grease capacity. Wipe off any excess grease squeezed out.

Safety Precautions

Proper jack stands should always be used when lifting a trailer to prevent injury. Additional safety tips include:

• Allow hubs to cool completely before disassembly to avoid burns.
• Wear protective gloves and eyewear when handling grease.
• Block wheels both in front and behind when working.
• Securely attach hub caps after packing bearings.

Taking basic safety measures helps avoid accidents while servicing trailer wheel bearings.

Warnings About Lubrication

To maximize bearing life and safety, keep these warnings in mind:

• Never mix greases – Compatibility varies between types.
• Avoid overheating – Excessive speed and heat degrades grease.
• Change fully submerged grease – Water washes out lubrication.
• Don’t overpack – Excess grease strains seals and wastes grease.
• Avoid contamination – Dirt ruins grease and damages bearings.

Proper lubricant selection along with careful repacking and sealing ensures the grease provides optimal protection.

Conclusion

Regular trailer bearing maintenance should not be neglected, even if the hubs lack grease fittings. With some careful work, fresh grease can be repacked through the seals into most sealed bearings at home. For maximum life and safety, bearings should be repacked every 1-2 years or before any extended trips. Proper lubrication will prevent premature wear, keeping your trailer rolling smoothly for miles down the road.