How to Work Out Trailer Bearings: Identify, Inspect, Service, and Adjust

To work out trailer bearings, identify the correct bearing sizes by reading the stamped part numbers or measuring the spindle and hub, then inspect, clean, repack or replace the bearings and races as needed, and set endplay to about 0.001–0.005 inches before securing with a new seal and cotter pin. This involves safe disassembly, careful inspection for wear, correct grease selection, and precise adjustment to ensure cool, reliable running.

What “work out” covers for trailer bearings

In practice, working out trailer bearings means three things: figuring out which bearings fit your hub and spindle, assessing whether the existing bearings are still serviceable, and performing proper maintenance or replacement followed by correct adjustment. Getting all three right prevents heat buildup, wheel wobble, brake damage, and roadside failures.

Tools and materials you’ll need

Before you begin, gather the essentials for safe lifting, measurement, cleaning, and reassembly so the job goes smoothly and you can verify correct fit and adjustment.

• Floor jack, wheel chocks, and jack stands (never rely on a jack alone)
• Lug wrench and torque wrench (for wheel lugs and bearing preload setting)
• Slip-joint pliers, needle-nose pliers, and a drift/punch
• New cotter pins or tang washer; new grease seal(s)
• Brake cleaner or solvent, shop towels, nitrile gloves, safety glasses
• High-temp NLGI #2 wheel bearing grease (marine-grade for boat trailers)
• Calipers or micrometer (to measure spindle diameters and seal bore)
• Replacement bearings and races (if worn), and a seal driver or appropriate socket

Having the right kit from the start reduces downtime and the risk of reusing worn or contaminated parts, which can lead to premature failure.

Identify the correct bearings for your trailer

To determine the exact bearings your trailer uses, rely on the stamped part numbers first, then confirm with measurements and axle information. This ensures you buy the correct parts and seals.

1. Read the numbers: Most bearings and races have part numbers (e.g., L68149, L44649) laser-etched or stamped on their sides—wipe clean and note them.
2. Measure if numbers are unreadable: Use calipers to measure spindle journals (inner and outer) and the hub’s seal bore. Record to the thousandth of an inch or hundredth of a millimeter.
3. Check axle/hub documentation: Look for an axle tag (often on the axle tube) for capacity (e.g., 3,500 lb) and manufacturer; cross-reference with parts catalogs.
4. Note hub type and wheel pattern: Idler vs. brake drum, and wheel bolt pattern (e.g., 5 on 4.5 in). These details help find matching kits.
5. Buy matched sets: If replacing, purchase bearings with their races and the correct seal as a matched kit to ensure compatibility.

Combining part numbers with precise measurements eliminates guesswork and helps avoid returns or ill-fitting components that could damage the hub.

How to check if your bearings need service or replacement

Before disassembly, look and listen for telltale symptoms of bearing wear. If any are present, plan on a full inspection and likely replacement.

• Excessive wheel play: Rock the tire at 12 and 6 o’clock—noticeable clunk suggests loose or worn bearings.
• Noise: Growling or rumbling while spinning by hand indicates pitting or spalling.
• Heat: After towing, hubs should be warm but not painfully hot to the touch; a hot hub signals preload or lubrication issues.
• Grease leakage: Grease flung onto the wheel or brakes points to a failed seal or overfilled hub.
• Contamination: Water intrusion (milky grease) or rust suggests compromised lubrication and likely replacement.

Any combination of heat, noise, play, or contamination warrants immediate service—bearings degrade quickly once lubrication is compromised.

Safe removal and inspection

Work methodically and keep parts in order. Cleanliness matters—dirty assembly shortens bearing life.

1. Secure the trailer: Chock opposite wheels, break lugs loose slightly, jack and support with stands, then remove the wheel.
2. Remove dust cap: Pry off carefully; for EZ Lube/Bearing Buddy styles, follow the manufacturer’s directions.
3. Extract retainer: Remove cotter pin or bend back the tang washer; remove spindle nut and washer.
4. Withdraw hub: Slide off the hub/drum; catch the outer bearing as it comes free.
5. Remove seal and inner bearing: Pry out the grease seal without gouging the hub; pull the inner bearing.
6. Clean thoroughly: Use solvent to clean bearings, races, spindle, and hub. Dry with lint-free towels.

Keeping track of the order and orientation of parts simplifies reassembly and helps identify wear patterns during inspection.

Evaluate bearing and race condition

After cleaning, examine all rolling surfaces under bright light. Replace bearings and their races as a set if any defect is found.

• Pitting or flaking (spalling) on rollers or races
• Discoloration (blue/brown) from overheating
• Scoring, brinelling (indentations), or ridges on races
• Loose, cracked, or worn cages
• Roughness when rotating the bearing by hand

If there’s any doubt, replace both bearings and both races with matching parts, plus a new seal; it’s an inexpensive safeguard against hub failure.

Repack or replace bearings

If bearings and races are good, repack with fresh grease; otherwise, drive out old races and install new matched races and bearings before packing.

1. Install new races (if needed): Drive out old races with a punch, then seat new races squarely using a race driver until fully seated.
2. Pack bearings: Hand-pack or use a bearing packer to force NLGI #2 wheel bearing grease through until it extrudes from all roller voids.
3. Grease the hub and seal lip: Lightly coat the hub cavity and apply grease to the new seal’s lip.
4. Install inner bearing and seal: Place the inner bearing, then drive in the new seal flush and even.
5. Refit hub: Slide the hub onto the spindle carefully to avoid damaging the seal.
6. Install outer bearing, washer, and spindle nut: Prepare for adjustment steps next.

Using fresh grease and a new seal prevents contamination and leakage, while proper race installation ensures smooth, long-lasting operation.

Set correct endplay and reassemble

Proper adjustment minimizes heat and wear. The goal is slight endplay (typically 0.001–0.005 inches), not preload. Always follow your axle maker’s spec if provided.

1. Seat the bearings: While rotating the hub, tighten the spindle nut to about 15–30 ft-lb to fully seat the bearings and races.
2. Back off completely: Loosen the nut to remove preload.
3. Final adjustment: Finger-tighten, then back off about 1/6 to 1/4 turn. Verify slight endplay by hand or with a dial indicator (0.001–0.005 in).
4. Secure the nut: Align the castellations and insert a new cotter pin, or set the tang washer per design.
5. Reinstall dust cap: Tap on evenly; for EZ Lube/Bearing Buddy, do not over-pressurize—stop when the piston moves or resistance rises.
6. Wheel installation: Torque lug nuts to the wheel/hub spec in a star pattern; recheck torque after 25–50 miles.

After adjustment, the hub should spin freely with no grind and only slight, detectable play. Excess heat on a short test tow indicates over-tightening or inadequate lubrication.

Maintenance intervals and on-road checks

Regular attention keeps bearings cool and reliable, especially under heavy loads, high speeds, or water exposure.

• Service interval: Inspect and repack annually or every 12,000 miles; boat trailers may need service every season due to water intrusion.
• Post-service check: After 50–100 miles, feel hubs; warm is normal, hot is not. Recheck lug torque.
• On-trip monitoring: At fuel stops, touch-test hub temperature and check caps for grease seepage.
• Grease choice: Use high-temp NLGI #2 wheel bearing grease; for boat use, prefer marine-grade, water-resistant (e.g., calcium sulfonate complex). Do not mix incompatible greases.
• EZ Lube/Bearing Buddy: Spin the wheel while pumping; stop at first sign of movement or fresh grease at the outer bearing—overfilling can blow seals.

Consistent checks and correct lubrication dramatically reduce the odds of roadside bearing failures and brake contamination.

Common bearing setups (verify before purchase)

While you must confirm with part numbers or measurements, these patterns are frequently found on light- and medium-duty trailer axles.

• 3,500 lb axle (#84 spindle): Often inner bearing L68149 with race L68111; outer bearing L44649 with race L44610; common seal ID around 1.719 in (verify seal size).
• 2,000 lb axle: Often uses L44649 inner and outer; confirm seal size and hub style.
• 5,200–6,000 lb axles: Frequently use 25580 inner and LM67048 or similar outer; check documentation.

Treat these as starting points only—always match the stamped numbers or measurements to ensure the correct kit and seal.

Safety and environmental notes

Basic precautions protect you and your brakes while reducing mess and exposure to solvents.

• Always support the trailer with jack stands on solid ground.
• Avoid inhaling brake dust; older brake linings may contain hazardous fibers—use wet methods or brake cleaner.
• Dispose of used grease, seals, and solvent-soaked rags per local regulations.

These small steps make the job safer and help keep components clean and functional.

Summary

Working out trailer bearings means correctly identifying the parts, inspecting them for wear, and servicing or replacing them with care. Read or measure to confirm bearings and seal, clean thoroughly, use quality NLGI #2 grease, install new seals, and adjust to slight endplay (about 0.001–0.005 inches) before securing with a fresh cotter pin. Finish with a short test tow and temperature check, and maintain annually (or each season for boat trailers) to keep hubs cool and reliable.

How much play should there be in a trailer wheel bearing?

There should be a very small, barely perceptible amount of end play in trailer wheel bearings, typically around 0.001 to 0.005 inches (0.025 to 0.127 mm), achieved by first snugging the nut while spinning the wheel and then backing it off slightly. Too much play indicates a problem and can cause vibration and bearing wear, while excessive tightness will cause the bearing to overheat and fail.
 
How to Check for Play

1. Secure the trailer: Chock the wheels on the other side of the trailer to prevent movement. 
2. Lift the wheel: Jack up the trailer so the suspect wheel is off the ground. 
3. Check for movement: Grab the tire at the 3 o’clock and 9 o’clock positions and try to shake it back and forth. 
4. Evaluate the play:
   • No play is ideal: A properly adjusted wheel bearing will have no noticeable looseness. 
   • Excessive play: If you can feel or hear significant movement, the bearing is too loose. 
   • Wheel spins freely: When spinning the wheel, it should rotate smoothly without any binding or grinding. 

How to Adjust for Proper End Play

1. Create tension: With the wheel off the ground and spinning, tighten the adjusting nut until you feel slight resistance or “binding” in the bearing. 
2. Back off: Loosen the nut about a one-sixth to one-quarter of a turn (or about 1/8 to 1/4 turn) to allow for the specified end play. 
3. Check for play again: Repeat the shake test to ensure there’s no excessive movement but still allows for free spinning. 
4. Secure the nut: Reinstall the keeper (like a cotter pin or castle nut) and tap the dust cap back into place. 

Signs of a Problematic Bearing

• Grease leaks: You may see grease leaking from the dust cap onto the wheel or trailer frame. 
• Excessive heat: The wheel hub will feel very hot to the touch during stops. 
• Noisy operation: A grinding, rumbling, or humming noise may be heard when the wheel is spinning. 
• Steering wheel vibration: Vibrations felt in the vehicle, especially when turning, can also be a sign of bad bearings. 

How do I know what size trailer bearings I need?

To measure trailer bearings, first, try to find the part number stamped on the bearing itself. If the number is worn or missing, you’ll need a digital caliper to accurately measure the inner diameter (ID) (where the bearing sits on the spindle) and the outer diameter (OD) (the part that fits into the hub). Measure the width of the bearing with the caliper as well. You can also measure the spindle with a caliper to get the bearing’s ID. Always clean the parts and double-check your measurements.
 
This video demonstrates how to measure trailer bearings using a digital caliper: 57sBlueswift AxlesYouTube · Mar 25, 2025
1. Find the Part Number (Most Accurate Method)

• Remove the hub and inspect the inner and outer bearing cones and races. 
• Look for a stamped part number on each component. 
• Use these numbers to look up the correct replacement parts online or at an auto parts store. 

2. Measure the Spindle with a Digital Caliper

• Clean the spindle thoroughly to remove dirt and grease. 
• Use a digital caliper to measure the diameter of the spindle where the bearings rest. This gives you the bearing’s inner diameter (ID). 
• Also, measure the width of the spindle for the bearing’s width. 

This video shows how to measure the spindle diameter: 49sTrailerPartsYouTube · May 9, 2024
3. Measure the Bearing with a Digital Caliper

• Remove the bearing from the hub. 
• Use a digital caliper to measure the inner diameter (the part that fits the spindle) and the outer diameter (the part that fits into the hub). 
• Measure the width of the bearing. 

Important Tips

• Use a digital caliper: Rulers and tape measures are not accurate enough to get the precise measurements needed for trailer bearings. 
• Measure both bearings: A trailer hub uses two different-sized bearings, an inner and an outer, plus their corresponding races and a grease seal. 
• Record all dimensions: Note the ID, OD, and width of both the inner and outer bearings. 
• Seek professional help: If you’re unsure, consult a local mechanic for assistance. 

How do I know what size spindle my trailer has?

To measure a trailer spindle, you must first remove the wheel and hub assembly from the axle. Then, use a digital caliper to measure the diameter of the spindle at the points where the bearings and grease seal ride. For a more precise measurement, measure where the bearings and seal sit on the spindle.
 
Tools You’ll Need 

• Jack: and jack stands to lift and stabilize the trailer
• Lug wrench: to remove lug nuts
• Screwdriver: to remove the dust cap
• Digital caliper: for accurate diameter measurements
• Flexible tape measure: (optional, if no caliper is available)
• Grease and rags: to clean the spindle and view bearing numbers

This video demonstrates how to remove the wheel hub assembly from a trailer spindle: 53sPenner Trailer Sales, LLCYouTube · Oct 15, 2024
Step-by-Step Guide

1. Secure the Trailer: Use a jack to lift the trailer and place jack stands under all corners for stability. 
2. Remove the Wheel: Use a lug wrench to remove the wheel nuts and take off the wheel. 
3. Access the Spindle: Remove the dust cap from the center of the hub to expose the axle nut. 
4. Remove the Hub Assembly: Take off the axle nut and pull the entire wheel hub assembly off the spindle. 
5. Clean the Spindle: Clean the spindle where the bearings and grease seal ride to see the measurements clearly. 
6. Measure the Spindle Diameter: 
   • Using a digital caliper (preferred): Place the caliper at the bearing and seal locations on the spindle. The resulting number is the diameter you need. 
   • Using a flexible tape measure (if no caliper is available): Wrap the tape around the spindle at the bearing and seal locations. This gives you the circumference, which can be used to determine the diameter. 

You can watch this video to learn how to use a digital caliper to measure trailer axle wheel bearings and grease seals: 59sBlueswift AxlesYouTube · Mar 21, 2025
What to Do With the Measurement

• The diameter measurements you take will be used to find the correct inner diameter for replacement bearings and grease seals. 
• The information you gathered will help you match the correct hub and spindle for your trailer. 

What size bearing is a 3500 lb trailer axle?

A standard 3500 lb trailer axle bearing set uses an L68149 inner bearing (with a 1.378″ ID) and an L44649 outer bearing (with a 1.063″ ID). These bearings fit onto a #84 spindle and are paired with races L68111 and L44610, respectively. The parts will often be stamped with their numbers, which can be a helpful way to verify the correct size. 
Key Bearing Information 

• Inner Bearing: L68149 (1.378″ inside diameter)
• Outer Bearing: L44649 (1.063″ inside diameter)
• Spindle Type: #84 Spindle

How to Verify Your Specific Size

1. Check for Stamped Numbers: The easiest way to confirm the correct bearing is to find the part number stamped on the side of the existing bearings or bearing races. 
2. Confirm the Spindle Size: Look for the size of your spindle. The #84 spindle is standard for many 3500 lb axles, but a spindle manufacturer’s information is the most reliable source. 
3. Check the Hub: The hub assembly will often indicate the bearing and spindle it’s designed to fit. 

What to Look For
You’ll typically need a complete bearing kit that includes: L68149 (inner) and L44649 (outer) bearings, Corresponding races (L68111 and L44610), Grease seal, Dust cap, and Cotter pin.