Heaviest cart load — up to 20,000 lb total (4 casters)
6″ x 2″ red poly at 5,000 lb per caster is the top of this collection. Available in swivel, rigid, and total-lock brake. For 4-caster carts up to 20,000 lb total static load.
Standard heavy industrial — 8,000-16,000 lb total
5″ x 2″ red poly at 4,000 lb per caster is the mid-tier workhorse. Total-lock brake variants for parked-cart applications. Used on most heavy industrial transport.
Medium-heavy carts — 4,400-11,200 lb total
4″ x 2″ red poly at 2,800 lb per caster. The lighter end of red poly — appropriate for medium-heavy carts where the cast iron capacity is needed but 5,000 lb per caster is overkill.
If you need higher capacity than 5,000 lb per caster
Step up to poly-on-iron up to 8,000 lb with the 4-1/2″ x 6-1/4″ plate. Above 8,000 lb you’re in kingpinless and dual-wheel territory.
If you need washdown corrosion resistance
Cast iron rusts in wet environments. Switch to polyurethane on aluminum for food, pharma, marine, or washdown applications. Same tread material, corrosion-proof aluminum hub.
Why red? Is the color just marketing or does it indicate something specific?
The red tread color is an industry-wide visual marker for premium-grade polyurethane on iron — specifically the higher durometer (95A) tread that delivers the heavy-capacity ratings. Standard polyurethane (80A-85A durometer) is typically gray, black, or amber. The red signals to a mechanic or maintenance tech that this is HD spec, not standard-grade poly. Useful when sourcing replacements from inventory — the visual tells you the capacity tier at a glance.
What’s the difference between red poly and standard poly on iron?
Capacity. Red poly on iron in this size class hits 2,800-5,000 lb per caster. Standard polyurethane on iron in the same wheel sizes runs 1,100-2,500 lb. The capacity difference comes from a harder polyurethane formulation (95A vs 80A durometer), a heavier-gauge cast iron core, and stronger bearing assemblies. For applications under 2,000 lb per caster, standard poly on iron is fine and cheaper.
Will red poly mark light-colored finished floors?
No. Polyurethane is inherently non-marking regardless of color. The red tread leaves no visible residue on tile, sealed concrete, epoxy, or laminate floors. The dye in the polyurethane is bonded into the material, not surface-applied. Service life on smooth indoor concrete: 8-12 years at rated capacity.
Are total-lock brake variants available in all sizes?
Yes — total lock (locks both wheel rotation AND swivel raceway) is stocked in the 4″, 5″, and 6″ sizes as both individual casters and 4-pack sets. The 8″ size is available with side-lock brake. For most heavy industrial cart applications, the standard 4-caster pattern is 2 swivel-with-brake (front) + 2 rigid (rear) for predictable straight-line tracking.
Will these handle towline operations?
Standard red poly on iron is rated for manual cart and powered-cart operation up to about 2 mph. For sustained towline operations at higher speeds, specify kingpinless construction — see our Kingpinless Casters collection. The kingpin in conventional swivel casters is the failure point under high-cycle towline duty.
