The 351-675 lb spec matrix
At this tier the wheel material choice drives most of the outcome. Match the wheel to the floor and the environment; the rig and bearing follow from there.
| Wheel |
Typical cap (this tier) |
Best floor |
Where it fits |
| Polyurethane on polyolefin |
350–500 lb |
Finished concrete, tile |
Service & utility carts, light shop |
| Polyurethane on aluminum/iron |
500–675 lb |
Industrial concrete |
Tool carts, light warehouse equipment |
| Phenolic |
500–675 lb |
Hard, dry industrial |
Oil/solvent areas, low-rolling-resistance routes |
| Pneumatic |
350–500 lb |
Outdoor, rough surfaces |
Yard carts, outdoor service equipment |
| Thermoplastic rubber |
350–450 lb |
Finished floors, quiet zones |
Institutional carts, quiet-route equipment |
Static vs. dynamic — the number that fails fleets — Caster spec sheets list two load ratings. Static is what it holds parked; dynamic is what it holds rolling, and dynamic is only 60–80% of static. At this tier, where carts roll constantly, you have to size against the dynamic number. A caster labeled “500 lb” on the static line may only be a 350–400 lb caster while moving. Confusing the two is the most common reason a correctly-calculated cart still fails early.
The calculation, worked through
Total the equipment weight plus the load weight. Multiply by your safety factor — 1.3–1.5× for smooth floors and gentle use, 2× for typical carts and racks, 3–4× if there’s towing, ramps, debris, or impact. Divide by the number of casters. If your equipment has one rigid pair and one swivel pair, size every caster to the same number — load shifts around as the cart turns and you can’t assume even distribution.
Worked example: a 1,400 lb load on a 150 lb cart, four casters, typical use (2× safety factor). (1,400 + 150) × 2 ÷ 4 = 775 lb per caster — that lands one tier up, in the 676-1,250 lb band. Same load at a 1.5× factor lands at 581 lb — inside this tier. The safety factor you pick decides the tier, which is why picking it honestly matters.
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 (you are here)
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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
351-675 lb tier FAQs
Why does the same wheel show a range of capacities in this tier?Core material. A polyurethane tread on a polyolefin core carries less than the same tread on an aluminum or cast-iron core. The tread you see is the same; the core you don’t see sets the rating.
What safety factor should I actually use?2× is the safe default for most carts, racks, and benches. Drop to 1.3–1.5× only for smooth floors and rarely-moved equipment. Go to 3–4× for towing, ramps, debris, or impact loading.
Can I mix wheel materials on one cart?Don’t. Mixed materials roll at different resistances and wear at different rates, which makes the cart track crooked and shifts load unevenly. Match all four.
Is phenolic worth it at this tier?Phenolic shines in oil and solvent areas where polyurethane degrades, and it has low rolling resistance. It’s hard and noisy, so it’s the wrong pick for finished-floor or quiet-route work.
My math is right at 675 lb — buy here or step up?Step up. Sizing at the exact ceiling of a tier leaves no margin for overload, threshold impact, or the static-vs-dynamic gap. The 676-1,250 lb tier gives you headroom.
Run your numbers with us
Send equipment weight, load weight, caster count, and floor type. We’ll work the calculation and confirm the right tier and wheel.
Call 844-439-4335
