Caster Dimensions and Configuration
A guide for specifying industrial and commercial casters
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.
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"
- 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
- 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.
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.
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
- Hub length: The side-to-side length of the hub as
measured from the wheel face side.
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