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How to Identify Your Trailer Axle β€” Capacity, Bolt Pattern, Bearings, and Measurements

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3500 lb Bearing Kit β€” EZ-Lube CapL68149 + L44649 β€” confirms 3,500 lb axleShop Now β†’5200-6000 lb Bearing Kit β€” EZ-Lube25580 + 15123 β€” confirms 5.2K-6K axleShop Now β†’7000 lb Bearing Kit β€” 25580 + 14125AConfirms 7,000 lb axle β€” no-cap styleShop Now β†’Dexter 10" Electric Brake Set β€” 3,500 lbFits #84 spindle 3.5K axlesShop Now β†’Dexter 12" x 2" Brake Set β€” 7,000 lbFits #42 spindle 7K axlesShop Now β†’
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Quick Answer

The axle label is on the center of the axle tube on the rear (back) side, facing the ground. It lists the axle's capacity, hub face, spring center, brake configuration, and lube type. If the label is gone, the capacity can also be determined from: the bolt pattern on the hubs, the bearing part numbers stamped into the bearings, or the tube diameter. All four methods are covered below.

Method 1 β€” Find and Read the Axle Label

Lay on your back under the trailer and look at the center of the axle tube facing downward. There will be a sticker or stamped number on the underside of the axle beam.

  • Dexter axles: A 9-digit serial number is etched into the tube. A separate sticker lists capacity, hub face, spring center, brake and lube configuration.
  • Lippert axles: The description number is formatted as HUB FACE / SPRING CENTER (e.g., "82/66" = 82" hub face, 66" spring center).
  • Label worn off? Try rubbing chalk over the stamp β€” the chalk fills the engraving and makes faded numbers readable. Spray paint works too: brush a thin coat on the tube and wipe before it dries.
  • Still can't read it? Use Methods 2–4 below.

Method 2 β€” Bolt Pattern (Fastest ID)

Count the wheel studs on one hub and measure the bolt circle. Bolt pattern strongly indicates axle capacity:

Bolt Pattern Axle Capacity Notes
4 on 4" 2,000 lb Small utility and boat trailers
5 on 4.5" 3,500 lb (#84 spindle) Most common utility and dump trailer axle
5 on 5" 3,500–5,200 lb Some Dexter and Lippert variants
6 on 5.5" 5,200–6,000 lb Mid-duty tandem axle trailers
8 on 6.5" 7,000–8,000 lb Heavy dump trailers, equipment haulers

How to measure bolt pattern: For 4, 6, or 8-lug hubs β€” measure center-to-center across two directly opposite bolts. For 5-lug hubs β€” measure from the outer edge of one bolt to the center of the bolt two positions away. This gives you the bolt circle diameter.

Method 3 β€” Bearing Numbers (Most Precise)

Remove the grease cap from one hub and pull out the outer bearing. The bearing cone part number is stamped directly into the metal. These numbers unambiguously identify axle capacity:

Inner Bearing Outer Bearing Axle Capacity
L44643 L44643 2,000 lb (BTR spindle)
L44649 L44649 2,200 lb (BTR spindle)
L68149 L44649 3,500 lb (#84 spindle) β€” most common
25580 15123 5,200–6,000 lb
25580 14125A 7,000 lb (#42 spindle)

Method 4 β€” Axle Tube Diameter

The tube diameter provides a rough capacity estimate when nothing else is readable:

Tube Diameter / Shape Approximate Capacity
1-3/4" round 2,000–2,200 lb
2-3/8" round 3,500 lb
3" round 5,200–6,000 lb
3-1/2" square tube 7,000 lb
4" square tube 8,000–10,000 lb

Key Measurements β€” Hub Face and Spring Center

When ordering replacement axles or parts, you need two measurements beyond capacity:

  • Hub face: Distance from the outside face of one wheel hub to the outside face of the opposite hub. This is the overall width of the axle assembly. Measure with a long tape measure from hub to hub.
  • Spring center: Distance between the centers of the two leaf spring mounting points (where the axle sits in the spring). This determines how the axle positions under the trailer frame. Measure center-to-center at the spring seats.
  • Lippert notation: Written as Hub Face/Spring Center β€” example "82/66" means 82" hub face, 66" spring center.

Frequently Asked Questions

My trailer has two axles. Do I need to measure both?
On a tandem axle trailer, both axles should be identical β€” same capacity, same hub face, same spring center. Measure or identify one and that applies to both. If you're replacing only one axle, the replacement must match the other exactly or your spring geometry and tire clearance will be off.
I know the capacity but need to find the right bearings. How?
Use the bearing number table above β€” it's the most direct method. If you know you have a 3,500 lb axle, you need L68149 inner and L44649 outer. If you have a 7,000 lb axle, you need 25580 inner and 14125A outer. The bearing kit product descriptions at AAA Trailer confirm which kit matches which axle.
How do I know if my axle has EZ-Lube or standard spindles?
Remove the grease cap and look at the end of the spindle. EZ-Lube spindles have a grease zerk fitting recessed into the end of the spindle. Standard spindles have a smooth end with no zerk. The presence or absence of the zerk is definitive β€” you can't confuse the two once you look.
⚠ Need Help Identifying Your Axle?

Call AAA Trailer at (517) 225-1991. Tell us the bolt pattern and the bearing numbers from inside one hub, and we can identify your axle and get you the right parts in under two minutes.