Caster Terminology

1. Overall Height — The vertical distance between the floor and the mounting point of the equipment.

2. Offset — The horizontal distance between vertical center lines through the king pin and the wheel center.

3. Swivel Radius — The horizontal distance from the vertical line of the king pin to the outside edge of the wheel tread. This dimension specifies the minimum distance required for the caster to swivel 360° when mounted.


Dynamic or Rolling Load — The load imposed upon a caster or wheel while in motion.

Static Load — The load imposed upon a caster while it is stationary.

Impact Load — A momentary load imposed upon a caster or wheel when a load is dropped on the equipment or it strikes an obstruction or experiences vibration.

4. Wheel Diameter

5. Tread Width


Steering — Steering is affected by the type of wheel, tread and swivel. Swivel offset is a factor in ease of steering. Too short a lead will increase steering effort, but too much lead can reduce load capacity and may cause wobble.

Rollability — Rollability is the ease with which a wheel or caster can be rolled. Rollability is affected by wheel size, type of tread and bearings. The larger the wheel, the easier it will roll. A hard, narrow crowned tread rolls easier than a flat soft tread on a smooth floor, but may be hard on floors. Soft treads protect floors and pass over floor obstructions more easily.