Rubber wheels and rubber-tread casters — the most-specified material for quiet, shock-absorbing, non-marking mobility. Five rubber families stocked at CasterHQ: cast-iron mold-on (1,300 lb), supreme rubber on aluminum (800 lb), super cushion non-marking (450 lb), gray thermo rubber TPR (600 lb), and rubber-on-plastic flat-free (650 lb). 2-1/2″ through 12″ diameter. Same-day ship from Mansfield, TX.
Five rubber families, each tuned to a different combination of capacity, noise, and floor protection. Match family to load and floor type.
| Family | Hub Core | Diameter | Capacity | Floor Marks? | Best For |
|---|---|---|---|---|---|
| Cast Iron Mold-On Rubber | Cast iron | 4"–12" | up to 1,300 lb | Slight | Heavy industrial carts, factory floors |
| Supreme Rubber on Aluminum | Aluminum | 6"–8" | up to 800 lb | None | Medical, lab, hospital — quietest premium |
| Super Cushion Rubber | Steel hub | 6"–8" | up to 450 lb | None | Hospitality, retail, office, finished floors |
| Gray Thermo Rubber (TPR) | Polyolefin | 2-1/2"–8" | up to 600 lb | None | Hospital beds, food service, sanitary |
| Rubber on Plastic (Flat-Free) | Polymer core | 8"–10" | up to 650 lb | None | Hand trucks, outdoor service carts |
| Hard Rubber | Steel hub | 3"–8" | up to 800 lb | Some | Cold storage, light industrial — lowest cost |
Total load divided by number of casters, then add 30-40% safety margin. Cast iron mold-on handles 1,300 lb per wheel. Aluminum-core supreme rubber tops out at 800 lb. Plastic-core families top at 450-650 lb. Match wheel capacity to your single-caster load with margin.
On finished floors (hospital, retail, office, hospitality): non-marking gray TPR, supreme rubber, or super cushion. On factory and warehouse concrete: any rubber family works. Avoid black hard rubber on light commercial vinyl — it leaves streaks.
Rubber families ranked quietest to loudest: supreme rubber on aluminum, super cushion, gray TPR, mold-on rubber, hard rubber. Aluminum-core supreme rubber is the medical-grade quiet standard. Mold-on cast iron is louder but bridges seams better.
Indoor only: any rubber family. Outdoor service: rubber on plastic (flat-free) or solid thermo rubber. Avoid cast-iron mold-on outside — the iron core rusts and the rubber tread cracks in UV after 2-3 seasons.
Supreme rubber on aluminum is the quietest production rubber family — the aluminum hub damps vibration that steel and cast iron transmit. Followed closely by super cushion (steel hub, soft tread) and gray TPR. All three are specified in medical, lab, and white-glove environments.
Most rubber families are non-marking when specified as such. Gray TPR, supreme rubber on aluminum, and super cushion non-marking are explicitly non-marking. Mold-on rubber is "slight-mark" — visible under heavy load on light floors. Black hard rubber is marking — do not specify on finished flooring.
Mold-on rubber bonds rubber to a metal hub (cast iron, steel, aluminum) — high capacity, heavy. Rubber-on-plastic bonds rubber to a polymer hub — lighter, lower capacity, no rust, often flat-free. Choose mold-on for indoor industrial; rubber-on-plastic for outdoor or weight-sensitive carts.
Indoor industrial use: 5-10 years for mold-on rubber, 3-7 years for cushion families. Outdoor: 1-3 years (UV cracks rubber). Bearing life usually exceeds tread life. The tread degrades faster than the hub — the wheel itself is rarely the failure point.
A non-marking wheel does not leave black, gray, or colored streaks on the floor. Achieved by using a light-colored rubber compound (gray TPR, white urethane) or a chemically inert compound (supreme rubber). The wheel does not stop wearing — it stops transferring color.
Most rubber families stiffen below 32°F and lose rolling efficiency. For cold storage: specify polyurethane or specialty cold-rated rubber. Thermo rubber and supreme rubber on aluminum are rated to roughly −20°F. Cast-iron mold-on stays flexible to freezing but is not optimal.
Gray TPR is the food-service standard — food-safe, non-marking, easy to sanitize. Supreme rubber on aluminum is also acceptable. Avoid black mold-on rubber and hard rubber in direct food contact areas — they shed black particles under wear.
Yes — the rubber tread bridges 1/8" to 1/4" floor seams and small debris better than rigid materials. For seriously uneven outdoor surfaces, step up to rubber-on-plastic flat-free or pneumatic. For factory floors with expansion joints, mold-on rubber is the standard.
