Most 3,500 lb trailer axles use an L68149 inner bearing (1-3/8 inch bore) and an L44649 outer bearing (1-1/16 inch bore). Lighter single-axle trailers use paired L44649/L44610 bearings, and 5,200 to 8,000 lb axles step up to 15123/15245 or 25580/25520 sets with 1-3/4 inch bores. This chart covers every common size, what trailer each fits, and how to identify what you have.
Contents
Trailer bearings are identified by standard Timken-style part numbers stamped on the bearing cone. The numbers below are the industry-standard set you will find on the overwhelming majority of US-built trailer axles:
| Axle Rating | Inner Bearing (cone/cup) | Outer Bearing (cone/cup) | Inner Bore | Typical Trailer |
|---|---|---|---|---|
| 1,000 to 1,500 lbs | L44649 / L44610 | L44610 pair (same) | 1-1/16 in | Small utility, jet ski, pop-up |
| 2,000 to 2,500 lbs | L44649 / L44610 | L44649 / L44610 | 1-1/16 in | Light utility, small boat |
| 3,500 lbs | L68149 / L68110 | L44649 / L44610 | 1-3/8 in | Most single-axle utility, boat, cargo |
| 5,200 to 6,000 lbs | 15123 / 15245 | 15123 / 15245 | 1-3/4 in | Heavy cargo, equipment, dual-axle |
| 7,000 to 8,000 lbs | 25580 / 25520 | 25580 / 25520 | 1-3/4 in | Car haulers, goosenecks, equipment |
Reading the chart: the inner bearing carries most of the load and is always the larger of the pair; the outer bearing just locates the hub. On a straight spindle both bearings share one bore size (common on light axles); on a stepped spindle the inner is larger. When someone says "trailer wheel bearing sizes" without context, nine times out of ten they own a 3,500 lb axle and need L68149 inner with L44649 outer.
Three ways, in order of reliability:
Nearly every single-axle utility, boat, and cargo trailer under 4,000 lbs GVWR rolls on a 3,500 lb axle with an L68149 inner and L44649 outer bearing. If you search "3500 lb axle bearing size," this is your answer: L68149 (inner, 1-3/8 in bore) and L44649 (outer, 1-1/16 in bore), with races L68110 and L44610 respectively. Both use a standard 1.719 inch spindle seal on the inner side, and a complete set — both bearings, both races, seal, and tang washer or castle nut hardware — typically costs 30 to 60 dollars.
Light spindles often run the L44649/L44610 pair on both ends of a straight spindle. Same part inner and outer makes reassembly foolproof, and everything about servicing them (pack, seat, torque to 20 to 25 ft-lbs, back off a quarter turn, lock) is identical to bigger axles.
Heavier spindles step to 1-3/4 inch bores: 15123/15245 on 5,200 to 6,000 lb axles, 25580/25520 on 7,000 to 8,000 lb axles. The two are easy to confuse because bores match — check the cup outside diameter (15245 cups are about 3.265 in; 25520 cups about 3.875 in) before ordering. Seals differ too: a 10-19 or 2.25 inch double-lip seal on 5,200 lb axles, a 10-36 style on 7,000 and up.
"Boat wheel bearings sizes" resolves to the same chart — boat trailers use the same axles as utility trailers. What differs is the environment: launching submerges hot hubs in cold water, which thermally shocks the bearings and, worse, pulls water past worn seals into the grease. Boat trailer hubs should use Marine-grade (NLGI GC-LB, water-resistant) grease, and bearing protectors or Oil-bath hubs are worth considering if you launch often. Practically: same bearing numbers, more frequent inspection — annually at minimum, and repack every season or every other season for frequent launchers. For the full procedure, see the bearing repack guide.
A failing bearing has a predictable lifecycle: it runs warm, then hot, then it smokes, then it welds itself to the spindle at 65 mph. The warm stage is where you win — and it is invisible from the driver's seat. The classic tell is the hub-touch test at every fuel stop, but a hub you can barely hold your thumb on is already deep into the failure curve.
A trailer monitoring system that streams axle temperature to your phone while you tow catches the trend hours earlier: a hub running 40 degrees hotter than its twin on the other side is a bearing asking for attention, and you get that alert while there is still a safe exit ramp ahead of you. See also why TPMS alone is not enough — pressure sensors cannot see a bearing dying.
L68149 inner (1-3/8 in bore) and L44649 outer (1-1/16 in bore), with matching L68110 and L44610 races. This is the single most common trailer bearing set in North America.
No — the standard numbers are shared across brands, but sizes differ by axle rating. Match by the stamped part number on your old bearing, or by spindle bore measurement.
A properly seated bearing has essentially zero perceptible play: a slight rotational drag, no rock. If you can rock the wheel at the 12 and 6 o'clock positions, it needs attention. Full walkthrough: how much play is acceptable.
You can, but you are already elbow-deep in the hub — replacing both bearings, both races, and the seal together is what the pros do, and the marginal cost is small.
Most 3,500 lb axles take a 1.719 inch double-lip seal; 5,200 lb axles take a 2.25 inch (10-19) seal. Bring the old seal to the counter or measure the spindle shoulder.
