How to read this comparison
Every cell below states what published manufacturer and industry guidance reports for the material class. Published capacity and temperature figures are per-publisher reference values, not ratings we extend to any order — the rating for your wheel size, bearing and duty is stated on the quotation. Where two publishers disagree, the table says so and turns the disagreement into a condition to specify rather than a winner to trust.
The comparison at a glance
| Decision factor | Polyurethane (PU) | Cast iron | Phenolic |
|---|---|---|---|
| Floor protection | High — published selection guidance describes PU as absorbing vibration, gripping concrete and steel floors and protecting finished flooring | Low — selection charts grade cast iron low on floor protection; guides explicitly avoid recommending metal wheels where floor protection matters | Better than cast iron, worse than PU — phenolic is published as non-marking and easier rolling on smooth floors |
| Noise | Moderate — quieter than metal wheels; softer rubber runs about 5–8 dB quieter still | Loud indoors — published comparisons flag metal wheels as noisy and shock-transmitting | Hard-tread noise — material guides group phenolic with hard treads that transmit noise and impact |
| Load capacity (published class bands) | Up to roughly 1,500 lb per 5-inch wheel in one published table; heavy lines higher — per-publisher reference | Highest — one selection chart grades cast iron 300–6,000 lb per wheel (large-bore lines beyond); replacement-wheel listings reach 40,000 lb at the largest diameters | High — the same selection chart grades phenolic lines to roughly 8,000 lb; one static-load table holds phenolic at 2,500 lb per caster overnight |
| Temperature | ~32–180 °F published window: softens above 180 °F, chunks past 200 °F, excluded below 32 °F | Highest — published charts rate cast iron −40 to +800 °F; bearings and lubricant usually limit first | One publisher holds phenolic to 325 °F continuous / 400 °F transient; another grades phenolic-type lines to +250 °F — confirm the compound, not the material name |
| Moisture and washdown | Resists moisture and mild chemicals; prolonged hot water/steam (hydrolysis) and oils attack the tread over time — sample-test in the actual fluid | Corrodes untreated; plated or stainless construction carries the wet duty | Disagreed: one material guide says phenolic should not be used in wet conditions (nylon instead); a wheel maker describes its phenolic as water-resistant and suitable for wet environments. Treat moisture tolerance as construction-specific — confirm at RFQ |
| Standing (static) load | Creeps — flat-spots when parked above roughly 60% of rated capacity for ~12+ hours | No creep — published flat-spot guidance states cast iron and forged steel do not cold-flow | Holds — one published static table carries phenolic at 2,500 lb per caster without creep, but confirm the specific compound |
| Typical floor pairing | Smooth to semi-smooth concrete, epoxy and finished floors | Rough concrete, steel grates, foundry and outdoor surfaces | Smooth, dry industrial floors |
| What the sources do not settle | Exact non-marking behavior by compound — require the compound class on the quotation for finished floors | A noise figure in decibels for cast iron versus polymers — no published measurement located | Phenolic moisture tolerance (see the disagreed row) — resolve with your floor's actual wet conditions |
Three decisions the table compresses
First, the floor decides more than the load. Published wheel-selection guidance asks for floor condition before anything else: hard treads perform better on soft or smooth floors, soft treads roll better on hard or rough ones, and every guide carries a special-floor checklist — tracks, gutters, grates, thresholds, seams, dock plates — because each concentrates load on a small contact patch. A material choice that ignores the worst floor section fails on the best one's behalf.
Second, standing loads are a materials question, not a ratings question. Industry failure-mode guidance is specific: polyurethane (with rubber and TPR) cold-flows under continuous static load above roughly 60% of rated capacity, while cast iron and forged steel do not creep at all and phenolic is published holding heavy static dwell. Fleets that park loaded for days are the one place where the hard-wheel column of this table outranks polyurethane's floor advantages — or where rotating parking positions and sizing under the dwell load keep PU in play.
Third, temperature figures move with the compound and the bearings. Cast iron wheels are published to +800 °F, but the same sources warn that bearing type and lubricant are typically the limiting factors. Phenolic's heat ceiling is published anywhere from +250 °F to 400 °F transient depending on the publisher and the construction. Ask for the wheel's own tested temperature statement and the bearing's limit as two separate numbers.
Where each material lands
Choose polyurethane when the floor is finished, the fleet works near people, and the load rolls rather than parks — it is the published general-industrial default for exactly that combination. Choose cast iron when heat, extreme load or abrasive surfaces would destroy a polymer tread, and the floor is rough or sacrificial. Choose phenolic when you need hard-tread load capacity and economy on smooth, dry floors — and resolve the moisture question in writing before the order, because the published guidance disagrees. The material-selection chart page walks the full class list including nylon and rubber; the flat-spot guide covers the static-load failure in depth.
What to confirm at quotation
- Per-wheel dynamic rating for your size, bearing and speed — class bands above are published references, not order ratings
- Temperature statement for both the tread compound and the bearing/lubricant, as separate figures
- Moisture and chemical exposure — for phenolic especially, written confirmation of wet-floor suitability for the specific construction
- Static dwell pattern (hours parked loaded) so the tread compound is sized against cold-flow, not just rolling load
- Floor condition — worst section, not average — including thresholds, seams and dock plates
- Non-marking requirement for finished floors, stated as a compound class