What order do trailer bearings go in?

When replacing or repacking trailer wheel bearings, it is crucial to install the bearings, races, seals, and other components in the proper order. Improperly installed bearings can lead to premature failure, overheating, and unsafe conditions while towing. In this article, we will cover the step-by-step process for correctly installing trailer wheel bearings.

Bearing Components

Before getting into the installation steps, let’s go over the key components that make up a trailer wheel bearing assembly:

• Inner bearing – Mounted on the inner side of the hub and directly contacts the spindle.
• Inner race – The inner bearing rides directly on this curved metal race.
• Hub – The wheel bolts onto the hub, which rotates around the spindle.
• Outer bearing – Mounted on the outer side of the hub next to the grease seal.
• Outer race – The outer bearing rides directly on this curved metal race.
• Grease seal – Seals the bearing grease inside the hub and keeps contaminants out.
• Spindle nut – Threads onto the spindle to hold the bearings and hub assembly in place.
• Spindle washer – Distributes the spindle nut clamping force evenly across the outer bearing.
• Cotter pin – Locks the spindle nut in place to prevent loosening.
• Dust cap – Covers the end of the hub to protect the grease seal and keep dirt out.

The inner and outer bearings are cone-shaped and ride on their respective inner and outer races. These components work together to allow the wheel hub to spin freely with minimal friction. Maintaining the proper amount of grease between the bearings and races is critical for smooth rotation and dissipating heat.

Step 1 – Pack Inner Bearing

The first step is to pack the inner bearing completely full of fresh trailer wheel bearing grease. Packing the bearing forces grease into the internal rollers and cavities within the bearing. This ensures the bearing has grease thoroughly worked throughout before installation.

Use a bearing packing tool, or small screwdriver, to force grease into the bearing while continuously rotating the bearing. The bearing will begin to fill from the inside out as the grease is pushed between each roller. Rotate and re-pack the bearing several times until you can visually confirm it is fully saturated within grease.

Step 2 – Install Inner Bearing

Once the inner bearing is fully packed with grease, slide it onto the trailer hub or spindle. The inner bearing gets pressed or slid completely into the inner bore of the hub. Push firmly to ensure the bearing is seated all the way in the hub.

If you are replacing the bearings but reusing the old hub, make sure to thoroughly clean any grease, dirt, or debris from the inner hub bore. Any contaminants left behind can damage the new inner bearing.

Step 3 – Install Inner Bearing Race

The inner bearing race or cup gets pressed into the hub bore with the curved or tapered side facing towards the inner bearing. Use a socket and hammer to tap the race evenly into place within the hub. Seat the inner race completely until it bottoms out.

When seating the race, be careful not to damage or dent the race surface. Any dents or deformations will grind away at the inner bearing causing premature wear. The inner race should be smooth, clean, and fully pressed in.

Step 4 – Install Hub Assembly

Now take the hub with packed inner bearing and race installed and slide it onto the trailer spindle. The inner bearing will contact the spindle directly. Some minor adjustment may be needed to align the hub bolt holes or inner race with the spindle.

Make sure the hub assembly spins freely without any grinding noises when rotated. This confirms proper clearance between the inner bearing and spindle.

Step 5 – Install Outer Bearing

Pack the outer bearing completely full of fresh grease just like the inner bearing in step 1. Once fully packed, take the outer bearing and install it into the outer bore of the hub. Press firmly to seat the outer bearing until it bottoms out.

When installed, the wide end of the tapered outer bearing should face towards the outside of the hub. Rotate the hub assembly to check that it still spins freely without binding.

Step 6 – Install Outer Bearing Race

Take the outer bearing race and tap it evenly into the outer hub bore with a socket and hammer. The curved or tapered side should face directly towards the outer bearing. Fully seat the race until it is bottomed out.

Check that the hub still rotates smoothly without rubbing or grinding noises. A slight end play or back and forth movement is normal at this stage.

Step 7 – Install Spindle Washer and Nut

Slide the spindle washer over the spindle and rest it against the outer bearing race. Now thread the spindle nut onto the spindle by hand until it is seated firmly against the spindle washer.

It is normal for there to be a slight gap between the spindle washer and nut. This gap will get removed once the nut is tightened down.

Step 8 – Tighten Spindle Nut

Using a torque wrench, tighten the spindle nut to the manufacturer’s torque specification in an incremental cross pattern. For example, tighten to 50 ft-lbs, then loosen, then retighten to 100 ft-lbs, then back off, then final torque to spec (like 150 ft-lbs). This ensures an even adjustment of the bearing preload.

As you tighten, spin the wheel periodically to check for binding. Stop tightening once you feel a slight drag when spinning the wheel. Back the nut off just until the wheel spins freely again. At this point, the bearings are adjusted to a proper preload.

Step 9 – Install Cotter Pin

With the spindle nut adjusted, install a new cotter pin through the spindle nut and spindle hole. Bend the cotter pin prongs to secure it in place. The cotter pin will prevent the spindle nut from loosening over time.

If needed, tighten or loosen the nut further to align the cotter pin hole. Never back off the nut more than 1/6th of a turn when adjusting for the cotter pin.

Step 10 – Pack Hub with Grease

Apply a generous amount of fresh grease into the hub cavity between the inner and outer bearings. This provides a reserve of grease to keep the bearings lubricated while towing. Fill the void about halfway full with grease.

Some grease should be visible around the outer bearing when rotating the hub. Spin the wheel again and wipe away any excess grease that gets forced out.

Step 11 – Install Grease Seal

Gently tap or press the new grease seal evenly into the outer hub bore until fully seated. The seal’s spring tension should face towards the bearing to seal against grease leakage.

Be extremely careful not to damage, bend, or improperly install the seal, as this will lead to premature failure. Use a seal installation tool if available.

Step 12 – Install Dust Cap

The final step is to install the dust cap over the outer hub end. This protects the grease seal from road debris and contamination. Tap the dust cap into place with a hammer or press it on evenly until fully seated.

With that, the trailer wheel bearings are now properly repacked and adjusted. Always refer to the manufacturer’s instructions for torques specs and any additional steps required for your axle setup.

Tips for Replacing Trailer Wheel Bearings

Here are some additional tips to follow when servicing trailer wheel bearings:

• Always replace bearings in pairs – Don’t just replace one bearing, do both the inner and outer.
• Clean components thoroughly – Use brake cleaner to remove grease and debris from hub and other parts.
• Inspect for damage – Check bearings, hub, races, and seals for scoring, pitting, or cracks.
• Use high quality grease – Use a NLGI #2 rated grease made for wheel bearings.
• Adjust bearing preload properly – Follow the proper tightening pattern and torque spec.
• Re-check adjustment after 30 miles – The first trip sometimes further seats the bearings.
• Consider a complete hub overhaul – Worn races often call for complete hub replacement.

Troubleshooting Trailer Bearing Issues

Here are some common trailer wheel bearing issues and their likely causes:

• Overheating hub – Insufficient bearing lubrication, improper bearing adjustment, overloaded trailer, worn bearings
• Noisy bearing – Lack of lubrication, excessive preload, damaged components
• Loose bearing – Improper bearing adjustment, worn bearing/race surfaces
• Grease leakage – Damaged grease seal, over-filled hub cavity, hub seal installed incorrectly
• Bearing failure – Inadequate lubrication, excessive preload, incorrect components
• Uneven wear – Loose lug nuts, bent spindle, worn races, damaged bearings

Diagnosing the root cause of any trailer bearing issue will require a thorough inspection of all bearing assembly components. Look closely for any damage or abnormal wear patterns on the bearings, hub, or races. The need for frequent service may indicate underlying problems beyond just routine maintenance.

How Often to Repack Trailer Wheel Bearings

Trailer wheel bearing maintenance should be performed at least once per year or more often depending on usage and conditions. Here are some general repacking interval guidelines:

• 1-2 times per year for light or periodic duty
• 4-6 times per year for heavy duty daily use
• Every 10,000-20,000 miles for travel trailers
• Whenever bearings are submerged in water
• Whenever contaminants have entered the bearings
• Whenever wheel end components are disassembled

Keep in mind these are general recommendations – always follow the trailer manufacturer’s service intervals for the specific axle and bearing configuration. Repacking more frequently than required can actually wash out grease and lead to premature wear.

Conclusion

Proper wheel bearing order, adjustment, lubrication, and maintenance are critical to the safe operation of any trailer. Always use high quality bearing components and obey the manufacturer’s repacking and replacement intervals. When in doubt, have a professional service shop handle any bearing maintenance or repairs. Taking time to repack bearings annually and perform thorough inspections can help prevent catastrophic failures and accidents when towing trailers at highway speeds.