Why do bearings need a minimum load?

Rolling bearings need a minimum load to ensure proper rolling contact between the rolling elements and raceways. Without sufficient load, the balls or rollers may slide (skid) instead of roll, causing smearing damage, increased heat, and premature failure.

What causes bearing skidding?

Skidding occurs when the friction force is insufficient to maintain rolling contact. This happens at high speeds with light loads, especially with grease lubrication. The rolling elements accelerate in the unloaded zone and decelerate in the loaded zone, causing sliding.

How is the minimum load factor kr determined?

The minimum load factor kr depends on the bearing type: approximately 0.01 for deep groove ball bearings, 0.02 for cylindrical roller bearings, and 0.02 for spherical roller bearings. These values account for the internal geometry and contact conditions.

Does lubrication type affect minimum load?

Yes. Grease-lubricated bearings generally require higher minimum loads than oil-lubricated ones because grease has higher viscous drag, especially at startup. The kinematic viscosity used in the formula should reflect the actual lubricant at operating temperature.

What if my actual load is below the minimum?

If the actual load is below the minimum, you can: apply a preload (axial spring), use a heavier bearing arrangement, increase the load path, or switch to a bearing type with lower minimum load requirements. For vertical shafts, adding a spring-loaded washer is common.

Free Engineering Tool #047

Bearing Minimum Load Calculator

Calculate the minimum radial load required to prevent roller/ball skidding. Enter bearing dimensions, speed, and lubrication type.

Skidding Prevention Grease / Oil Ball & Roller

Bearing Bore d (mm)

Bearing OD D (mm)

Speed (RPM)

Kinematic Viscosity ν (mm²/s at operating temp)

Bearing Type

Lubrication Type

Quick presets

Results

Minimum Radial Load F_min

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Mean Diameter dm

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Factor kr

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ν × n Product

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Minimum Load Formula (Simplified)

The minimum radial load to prevent skidding is estimated as:

k_r — bearing type factor (0.01 for DGBB, 0.02 for CRB/SRB)
ν — kinematic viscosity at operating temperature (mm²/s)
n — rotational speed (RPM)
d_m — mean bearing diameter = (d + D) / 2 (mm)

Mean Diameter

Typical kr Values

Bearing Type	k_r
Deep groove ball bearing	0.01
Angular contact ball bearing	0.015
Cylindrical roller bearing	0.02
Tapered roller bearing	0.018
Spherical roller bearing	0.02

Practical Example

Example — 6208 Deep Groove Ball Bearing

Given: d = 40 mm, D = 80 mm, n = 3000 RPM, ν = 20 mm²/s, oil lubrication

d_m = (40 + 80) / 2 = 60 mm

F_min = 0.01 × (20 × 3000)^2/3 × 60³ / 1000

= 0.01 × 3915 × 0.216 = 0.85 kN

⚠️ Note: This is a simplified estimation. For critical applications, consult the bearing manufacturer’s specific minimum load guidelines. Actual minimum load depends on internal clearance, cage type, and lubricant properties.

Bearing Minimum Load Calculator | Prevent Skidding | Free Online Tool

Published by admin on February 15, 2026 February 15, 2026

Results

Minimum Load Formula (Simplified)

Mean Diameter

Typical kr Values

Practical Example