Step 1: Calculate Your Load Capacity
Load capacity is the first and most important specification. Getting it wrong — in either direction — causes problems: undersized casters fail prematurely or create safety hazards; oversized casters are unnecessarily expensive and may have larger wheel diameters that change equipment height.
The formula:
Load per caster = (Equipment weight + Max load weight) × 1.25 ÷ Number of casters
Then add a 25–30% safety margin to the result.
For example: a supply cart weighing 80 lbs, loaded with 300 lbs of supplies, on 4 casters: (80 + 300) × 1.25 ÷ 4 = 119 lbs per caster. With a 30% safety margin, specify casters rated at 155 lbs minimum. A 200 lb-rated caster is the appropriate choice.
For dynamic applications — equipment pushed over thresholds, ramps, or elevator gaps — increase the dynamic load factor from 1.25 to 1.5 or higher.
Step 2: Choose the Right Wheel Diameter
Larger diameter wheels roll more easily over obstacles and floor transitions, reduce rolling resistance, and distribute load over a larger contact patch (protecting floors). Smaller diameter wheels offer a lower profile and tighter turning radius.
- 2"–3" — light loads, tight spaces (IV poles, small instrument carts)
- 4"–5" — the universal standard for most commercial and healthcare applications
- 6"–8" — heavy loads, uneven surfaces, outdoor use (industrial, resort grounds equipment)
- 10"+" — very heavy industrial loads, rough terrain
A useful rule of thumb: for every 1" of floor obstacle or gap you need to cross, use at least 3" of wheel diameter.
Step 3: Select Your Tread Material
Tread material determines rolling resistance, noise level, floor protection, and chemical resistance. It is often the deciding factor for facilities with premium flooring or regulatory requirements.
| Material | Hardness | Best For | Floor Types | Pros | Cons |
|---|---|---|---|---|---|
| Polyurethane (PU) | Shore A 70–95 | Healthcare, hospitality, food service | LVP, tile, epoxy, hardwood | Non-marking, quiet, durable, easy to clean | Can flat-spot under static loads |
| Thermoplastic Rubber (TPR) | Shore A 60–80 | Healthcare, retail, light industrial | All hard floors | Excellent floor protection, very quiet | Lower load capacity than PU |
| Nylon | Shore D 60–70 | Industrial, warehouse, dry food service | Concrete, epoxy | Very high load capacity, chemical resistant | Loud, marks soft floors |
| Phenolic Resin | Shore D 80+ | Cold storage, high-temp industrial | Concrete only | Handles extreme temps, very hard | Loud, damages most floors |
| Stainless Steel | N/A | Sterile/wet environments | Hard floors only | Fully sanitizable, corrosion-immune | Very loud, will damage floors |
| Rubber (standard) | Shore A 40–60 | Light-duty, outdoor | Most surfaces | Quiet, good grip | Black rubber marks light floors |
Step 4: Pick the Correct Mount Type
How the caster attaches to your equipment is a spec that must match exactly — a wrong mount type means a caster that won't fit or won't hold.
- Plate mount — a flat metal plate bolted to the equipment frame. The most common type for heavy-duty applications. Verify the hole pattern dimensions (bolt spacing) before ordering.
- Stem mount — a threaded or grip ring stem that inserts into a socket in the equipment leg. Common on lighter carts, IV poles, and chairs. Verify stem diameter and length.
- Expanding adapter — for hollow tube legs without a pre-drilled stem socket. The adapter expands inside the tube. Verify tube inner diameter.
- Bolt hole / single hole — a single centered bolt for light-duty applications.
Step 5: Decide on Locking / Braking
Not all equipment needs locking casters, but the type of lock matters as much as whether you need one:
- No lock — acceptable for equipment that is always in motion or anchored another way
- Wheel brake only — stops rolling but allows the swivel to spin; the equipment can still pivot in place
- Swivel lock only — holds the wheel direction but allows it to roll; useful for towing applications
- Total-lock (dual-lock) — locks both wheel and swivel simultaneously; required for hospital beds, crash carts, and NFPA 101 egress equipment
- Directional lock — locks the swivel in a fixed forward direction; enables straight-line transport of long or heavy equipment
Step 6: Check Environmental Factors
Standard casters are designed for clean, dry, indoor environments at room temperature. If your application deviates from this, specify accordingly:
- Wet / washdown environments — stainless steel hardware, sealed bearings, nylon or PU wheels
- Salt air / coastal / pool areas — 304 or 316 stainless steel; avoid zinc or chrome plating
- Cold storage / freezers — low-temp grease, phenolic or nylon wheels (rubber hardens below freezing)
- High temperature — phenolic resin or cast iron wheels; avoid PU above 180°F
- Chemical exposure — verify tread and hardware compatibility with specific chemicals; nylon and stainless are broadly chemical-resistant
Step 7: Verify Regulatory Requirements
Depending on your industry, caster selection may be governed by specific codes and standards:
- NFPA 101 (Life Safety Code) — governs patient transport equipment in healthcare egress routes; requires total-lock or directional-lock casters
- NFPA 99 (Healthcare Facilities Code) — covers medical gas equipment and crash cart positioning; requires lockable casters
- NSF/ANSI 2 — food equipment standard; requires casters on food service equipment to be corrosion-resistant and cleanable to a smooth, crevice-free surface
- OSHA 1910.176 — material handling equipment; requires that industrial casters be rated for the actual maximum load
- ADA / ICC A117.1 — accessibility; equipment with casters in accessible routes must not create tripping hazards and must be repositionable by a single person