Caster Dimensions and Configuration

When casters are specified, certain measurements are always utilized to ensure the proper size of rig, wheel, and top plate. This page illustrates what each of the critical caster measures represents and how the overall caster is measured. If you have any questions, contact us for complete information. Our specialists help companies get the right rig and wheel for their application.

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Caster Dimensions

If you are replacing an existing rig, these are the basic ways to measure it. If you can see a manufacturer or model number on the existing caster, we can help you match it to a new caster.

• Rigid caster: This rig is stationary, side to side. The wheel can roll backward and forward, but cannot turn. Sometimes called a fixed or stationary caster.
• Swivel caster: These rigs turn 360˚ within their swivel radius. They allow a cart to make a quick, tight turn.
• Wheel diameter: This is the nominal diameter of the outside of the wheel. Most caster companies describe caster using wheel diameter as a primary measurement. For instance, this phenolic caster has an 8" diameter, and is usually called an 8" caster.
• Overall height: The distance from the bottom of the wheel to the top of the top plate. Casters are typically described by their wheel diameter, not by their overall height, so it's an important term to understand.
• Wheel width: This is often called the tread width. It represents the width of the wheel face, measured without a load present.
• Swivel lead: Sometimes called the offset, this is the perpendicular distance between the vertical centerlines of the kingpin and the axle of a swivel caster.

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Top Plate & Bolt Hole Spacing

• Top plate: Sometimes called the mounting plate, this piece attaches a caster to a cart, stand or other equipment.
• Top plate size: the width and length of a caster's top plate. This is critical to know when space is tight on an installation.
• Bolt holes: Mounting holes on a top plate that allow you to mount the caster on your equipment. 
• Bolt hole spacing: The distance between bolt holes. Many bolt hole patters are slotted for versatility.

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Wheel Dimensions

When looking for a replacement caster, determine the diameter of the existing caster wheel, measured on the front of the wheel (see below). For new casters, the application will determine wheel size. See our page on wheel specification for more information.

• Wheel diameter: (see above - this is the nominal diameter of the outside of the wheel.)
• Wheel width: (see above - this is the width of the wheel face, measured without a load present.)
• Axle diameter: The outside diameter of the wheel's axle.
• Hub length: The side-to-side length of the hub as measured from the wheel face side.

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