Capacity isn't only about wheel size — bearing class, swivel construction, hub material, and wheel material all multiply or divide the rated capacity at the same diameter. Pulling the right combination doubles or triples what the same-size standard caster can carry.
A 6" wheel rates ~1,200 lbs; the same compound at 8" rates ~1,800 lbs (50% more); 10" rates ~2,500 lbs. Diameter scales capacity roughly linearly within the same material family.
Forged steel rates 60% higher than poly at the same diameter. Phenolic rates 30% higher. The trade-off is floor compatibility (steel marks soft floors). Match material to floor + capacity need.
Roller bearings cap at ~1,500 lbs. Tapered rollers handle 2,500+ lbs and absorb axial loads (towed turning). Sealed precision adds 15% to roller. Maintenance-free is engineered for continuous duty without re-greasing.
Kingpin rigs fail at the kingpin under high cyclic loads. Kingpinless construction (Albion 110AX, 28AX) handles 40% more cyclic load and lasts 3-5x longer in continuous-duty applications.
A 6" × 2" rates 50-70% higher than 6" × 1.25" of the same material. Wider wheels distribute load over more contact patch and reduce floor pressure (psi). Trade-off: wider wheels need more swivel torque.
Office carts, light material handling. 3-4" diameter, standard poly or rubber.
Stockroom carts, light industrial. 4-5" diameter, sealed bearings standard.
Pallet carts, work platforms. 6-8" diameter, kingpinless or tapered roller.
Battery transfer, die carts, foundry. 8-12" forged steel or phenolic.
Aluminum hub + 85 Shore A urethane + maintenance-free precision bearings + kingpinless. Best capacity-to-force ratio on the market. Made in USA.
Maintenance-free sealed bearings + ergonomic urethane on cast iron core. 4-1/2" x 6-1/4" plate standard. Best price for maintenance-free in 5-8" range.
8" x 2" maroon kingpinless with sealed bearings. Best for heavy carts with frequent direction changes — kingpinless eliminates the highest-failure component.
Capacity values assume standard kingpin construction with roller bearings. Kingpinless construction adds ~40% cyclic capacity. Tapered roller bearings add 15-25%. Maintenance-free seals don't add capacity but extend service life 2-3x.
Above 5,000 lbs per caster, you're in custom-spec territory — 12"+ wheels, dual-wheel rigs, custom kingpinless geometries, specialty hub materials. Our engineering team has built specs up to 18,000 lb per caster for aerospace and foundry transfer.
Floors are never perfectly flat. Expansion joints, cracks, dock plates, and pallet edges cause one caster to lift at any moment. N-1 ensures the remaining casters carry full load when this happens. For 8+ caster carts, use N-2 (assume two lift-offs simultaneously due to longer deflection arm).
For static load, kingpinless adds about 5-10%. For cyclic load (the load the caster actually fails under in real service), kingpinless adds 40% and extends service life 3-5x. The kingpin is the most common failure point in heavy-duty service. Albion's 110AX and 28-series are kingpinless by default.
Always size to dynamic (rolling) rating, not static. Static rating is what the caster holds parked — 2-3x higher than dynamic for the same wheel. Dynamic rating is what survives in motion. Most failures trace to people specifying against static and overloading the dynamic capacity. Full guide.
Spec the next standard load class up — ideally 20-30% above calculated minimum. Tight-fit specs fail under unplanned overload, lift-off events, or bearing wear. Premium MAX Efficiency builds with maintenance-free bearings let you spec closer to minimum because they tolerate continuous duty without capacity decay.
Material strength and compression behavior. Forged steel carries 2-3x what poly carries at the same diameter because steel doesn't compress under load. Phenolic carries 30% more than poly because of its reinforced fiber matrix. Soft rubber compresses heavily and rates lowest. The trade-off is floor compatibility — steel marks soft floors that poly doesn't.
Yes — significantly. Continuous-duty (8-16 hours) generates bearing heat that reduces effective capacity by 25%. 24/7 operation requires 70% over the calculated minimum. The Premium MAX Efficiency build with maintenance-free bearings is engineered for this — it doesn't decay under continuous heat the way roller bearings do.
Generally no — mismatched diameters cause uneven load distribution and accelerated wear on smaller wheels. Exception: intentional designs like dock-stair carts where front wheels are larger by design. For all standard carts, use uniform diameter and width across all positions.
Often. The swivel raceway, kingpin, and bearing race are frequently the load-limiting elements — not the wheel. Kingpin construction caps swivel load at the kingpin's shear strength. Kingpinless designs distribute load across a larger raceway, raising the effective ceiling 40%. For carts above 1,500 lbs/caster, kingpinless is mandatory. See kingpin vs kingpinless.
In identical service, MAX Efficiency runs 3-5x longer than standard poly + roller bearing + kingpin. The aluminum hub doesn't crack like cast iron under shock loads. The maintenance-free bearings don't degrade from missed grease intervals. The kingpinless raceway doesn't develop kingpin shear over cyclic loads. Total cost of ownership over 5 years is typically 40% lower than standard despite the higher upfront price.
Escalate for: required capacity above 5,000 lbs per caster, dynamic shock loads (rail dollies, foundry transfer), 24/7 continuous operation, high-temp environments above 250°F, custom plate/stem geometry, or any aerospace / nuclear / pharmaceutical compliance spec. Submit your spec for engineering review — same-day response on standard configurations.
