Trailer Axle Bearing Life Calculator

L10 is the life that 90% of identical bearings reach under the same load and speed before the first sign of fatigue — equivalently, a 10% failure probability. Median life is roughly 5× L10. It is a statistical fatigue life, not a guarantee for any single bearing.

Set to the maker's endplay spec — typically snug the nut while spinning, then back off to 0.025–0.10 mm endplay. It changes life enormously: residual preload from an over-torqued nut adds a hidden axial P on every revolution and overheats the grease. If your hubs run hot to the touch after highway speed, re-check adjustment before blaming bearing quality.

C (basic dynamic load rating) is printed in every bearing datasheet — for example a 32310 taper roller (C ≈ 137 kN) on a 3.5 t trailer axle at ~80 km/h (≈420 rpm). P is the equivalent dynamic load: for pure radial load it is simply the radial force; with combined radial + axial load use P = X·Fr + Y·Fa with X and Y from the datasheet.

Because L10 assumes clean lubricant, correct fit and alignment. In practice most bearings die of lubrication failure, contamination, misalignment or fitting damage rather than fatigue. If yours fail early, check the actual load path and the grease before blaming the bearing.

Use p = 3 for ball bearings and p = 10/3 for roller bearings (cylindrical, spherical, taper). Rollers carry load on a line contact rather than a point, so their life is less sensitive to load — that is what the higher exponent encodes.