The heavy-duty caster glossary — what each term buys you
Kingpinless construction
The swivel rotates on a full circumferential raceway instead of a single central shaft. At 2,000+ lb, a kingpin shaft takes every impact and load-drop on a ~2″ circumference of metal — it deforms over time. Kingpinless distributes that force around the entire raceway. It is effectively the standard at this tier, not an upgrade.
Tapered roller bearings
Cone-shaped rollers that carry both the downward weight (radial load) and the cornering force (thrust load) at once. Ball bearings handle radial well and thrust poorly; at this tier the thrust load from turning under 3,000+ lb will destroy a ball bearing. Tapered roller is the answer.
Forged steel wheel core
The metal core inside the wheel, forged rather than cast. Forging aligns the grain structure along the load path so the core resists impact and shock without cracking. Cast iron cores work for pure static loads; forged steel is the standard once impact, towing, or rough floors enter the picture.
Drop-forged top plate
The mounting plate, drop-forged for grain alignment rather than cut from flat stock. At this tier the top plate carries 2,000-4,000 lb through its bolt holes — a forged plate resists the bolt-hole elongation and cracking that a stamped plate develops under heavy cyclic load.
Static vs. dynamic rating
Static is the parked rating; dynamic is the rolling rating, and dynamic runs 60–80% of static. At this tier the gap is large in absolute terms — a 4,000 lb static caster may be a 2,800 lb dynamic caster. Always size against the dynamic number for any equipment that moves.
Polyurethane durometer
The hardness of the polyurethane tread, measured on the Shore A or Shore D scale. Harder (95A and up) rolls more efficiently and carries more; softer (85A) absorbs floor debris and shock. At this tier, 95A on a forged steel core is the common default for smooth industrial concrete.
The speccing rules at the heavy-duty threshold
Size against the dynamic rating, not the static one — the gap is too large at this tier to ignore. Apply a 2× safety factor minimum, 3–4× if there’s any towing, ramps, debris, or impact. Size every caster to the same per-caster number even though only the swivels see cornering load — load shifts as the equipment turns. And confirm the floor: a four-caster set at this tier puts 8,000-16,000 lb onto the floor, and on smaller wheels the point load can approach the limit of standard industrial concrete.
The wheel-diameter and floor check — At 4,000 lb per caster, an 8″ wheel concentrates load over a small contact patch — potentially above the safe psi for standard 4″ concrete. Going to a 10″ or 12″ wheel spreads the load and drops the floor stress. If you’re at the top of this tier on small wheels, run the floor-loading math before you deploy.
The CasterHQ load-rating ladder — per caster
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Under 350 lb · Light duty — Office, display, AV, healthcare carts
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351-675 lb · Light-medium — Service carts, tool carts, utility trolleys
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676-1,250 lb · Medium duty — Industrial carts, racks, workbenches
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1,251-2,000 lb · Medium-heavy — Machinery bases, die carts, equipment
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2,001-4,000 lb · Heavy duty — Large machinery, transfer carts, tooling (you are here)
2,001-4,000 lb tier FAQs
Is this tier always powered movement?Effectively yes. A four-caster set here carries 8,000-16,000 lb — well beyond hand-push range. Plan a tugger, tow vehicle, or powered assist.
Do I always need kingpinless at this tier?For any application with movement, impact, or towing — yes, treat it as standard. The only exception is a near-permanent machinery base that moves once a year, where a heavy kingpin caster can still serve.
What wheel diameter should I use?10″ and 12″ dominate this tier. Bigger diameter spreads floor load, rolls easier, and crosses gaps better. Drop to 8″ only if height clearance forces it — and run the floor-loading math if you do.
Polyurethane or forged steel wheel?Polyurethane on a forged steel core for indoor concrete — floor protection plus capacity. Solid forged steel only for rail, hot environments, or floors where marking doesn’t matter.
Spec correctly at the heavy-duty threshold
Send load math, floor type, wheel diameter constraints, and movement method. We’ll confirm the construction and run the floor-loading check.
Call 844-439-4335
