Caster selection guide
Everything a buyer or design engineer needs to specify the right caster: load maths, charts, fitting types, brakes and the standards that apply in each market. Written for procurement and R&D teams, not for search engines.
How to choose a caster (7 steps)
- Calculate the load per caster — total weight ÷ number of casters × safety factor. See the formula below; this is where most specification errors happen.
- Check the floor. Hard treads (cast iron, steel, phenolic, nylon) roll easiest but damage concrete and are noisy. Resilient treads (PU, rubber, TPR, pneumatic) protect the floor and cut noise at the cost of higher rolling resistance.
- Choose the wheel diameter. Diameter is the single biggest factor in push effort — bigger wheels roll over debris and thresholds far more easily.
- Decide how it is moved. Manual push, or power-towed? Towing multiplies stress and speed, and requires roller, precision-ball or tapered-roller bearings.
- Pick the bearing. Plain bushing for light intermittent use, roller for medium, ball for smooth rolling, precision ball or tapered roller for heavy and towed duty. Sealed for dust, debris and washdown.
- Match the environment. Temperature, chemicals, washdown, hygiene, ESD and floor type all restrict the compound and the bracket finish.
- Check the geometry before ordering. Overall height, top plate size, bolt hole spacing, stem thread and swivel radius must match the existing frame — or the caster will not fit.
Load calculation & safety factor
Load capacity on a datasheet is per caster, for continuous manual propulsion on level floors. Never buy on the nameplate number alone.
- Level floor, four casters: safety factor 1.3–1.5.
- Uneven floor, four casters: divide by 3, not 4 — at any moment only three wheels carry the load. This is the single most common specification error we see.
- Off-centre loads: size the heaviest corner, not the average.
- Shock loading (dock plates, expansion joints, dropped loads) can momentarily exceed 3× the static load. Add capacity or choose a shock-absorbing design.
Worked example. A 400 kg trolley with a 300 kg payload on an uneven factory floor has 700 kg total. Over four casters that is 175 kg each — but on three wheels it is 233 kg, and with a 1.4 safety factor the real requirement is 327 kg per caster. The 300 kg model that looked fine on the datasheet is not sufficient; the 450 kg model is.
Load capacity chart
Typical dynamic capacity per caster for our standard series. Full data per SKU is on each product page.
| Wheel Ø | PU (94A) | Nylon PA6 | Elastic rubber | Cast iron | Typical use |
|---|---|---|---|---|---|
| 50 mm / 2" | 120 kg | 150 kg | 40 kg | — | Furniture, light display |
| 75 mm / 3" | 200 kg | 250 kg | 90 kg | — | Office, retail, light trolleys |
| 100 mm / 4" | 300 kg | 450 kg | 200 kg | 600 kg | Workshop, hospital, catering |
| 125 mm / 5" | 600 kg | 700 kg | 250 kg | 900 kg | Logistics, trolleys, OEM |
| 150 mm / 6" | 800 kg | 800 kg | 300 kg | 1,000 kg | Heavy trolleys, containers |
| 200 mm / 8" | 1,200 kg | 1,100 kg | 420 kg | 1,500 kg | Container handling, foundry |
Indicative values for level-floor manual propulsion. Towed, high-temperature and washdown applications derate — ask us for the test data for your duty cycle.
Size chart (mm ↔ inch)
| Metric | Imperial | Common overall height (swivel plate) | Typical load band |
|---|---|---|---|
| 50 mm | 2" | 78 mm | 40–150 kg |
| 75 mm | 3" | 112 mm | 90–250 kg |
| 100 mm | 4" | 140–143 mm | 200–600 kg |
| 125 mm | 5" | 165 mm | 250–900 kg |
| 150 mm | 6" | 191 mm | 300–1,000 kg |
| 200 mm | 8" | 241 mm | 400–1,500 kg |
Mounting types
| Type | How it fixes | Best for | Watch out for |
|---|---|---|---|
| Swivel plate | Four bolts through a flat top plate | Most trolleys, carts, containers | Needs a flat mounting surface |
| Rigid / fixed | Fixed top plate, no swivel | Paired with swivel casters for straight tracking | Never used alone on a four-wheel cart |
| Threaded stem | Threaded rod into a socket or tube | Furniture, racks, equipment frames | Thread pitch must match (M10/M12/M16, UNC) |
| Bolt hole | Single central bolt | Adding mobility to an existing OEM product | Load passes through one fixing point |
| Expanding stem | Rubber or square expander inside a tube | Hollow-leg furniture and display stands | Tube inner diameter must be measured |
| Kingpinless | Swivel raceway in the fork itself | Heavy duty, shock, towing, foundry | Higher cost — use only where justified |
Bearings
- Plain / bushing — light intermittent duty, cheapest, no maintenance.
- Roller bearing — medium duty, good value, tolerates impact better than ball.
- Single / double ball raceway — smooth rolling and easy swivelling on medium and heavy duty casters.
- Precision ball / tapered roller — heavy, high-speed and towed applications.
- Sealed — dust, debris, food and washdown environments; add it whenever the wheel will meet water or flour.
Brakes
| Brake | Locks | Typical use |
|---|---|---|
| Wheel brake | Wheel rotation only | Basic carts, shopping trolleys |
| Total lock | Wheel + swivel | Trolleys on ramps, medical equipment, workbenches |
| Directional lock | Swivel, in one direction | Long straight runs, towing stability |
| Central locking | All casters from one pedal | Hospital beds, medical carts |
EN / ISO standards
Caster standards are frequently mis-cited in supplier catalogues. These are the actual scopes:
| Standard | Applies to |
|---|---|
| EN 12526 | Vocabulary and recommended symbols |
| EN 12527 | Test methods and apparatus |
| EN 12528 | Castors for furniture |
| EN 12530 | Manually propelled institutional equipment |
| EN 12531 | Hospital bed castors |
| EN 12532 | Industrial castors, manual or power-towed, up to 1.1 m/s |
| EN 12533 | Over 1.1 m/s up to 4.4 m/s |
| ISO 22883 | Industrial applications up to 1.1 m/s (ISO equivalent of EN 12532) |
| IEC 60601 | Medical electrical equipment — applies to casters used on medical devices |
Do not cite EN 12532 for hospital-bed casters. Its own scope explicitly excludes hospital beds — the correct reference is EN 12531 (and EN 12530 for institutional equipment). Buyers who check will notice, and it undermines an otherwise strong technical submission.
Food & medical contact
"FDA-approved casters" is a phrase buyers search for, but the FDA does not approve casters. What exists is food-contact material compliance for the wheel compound — FDA 21 CFR and EU 10/2011 for the plastics in contact — plus hygiene-oriented design: sealed bearings, smooth non-porous surfaces, machine-washable constructions and stainless brackets.
For medical equipment, the requirement is usually a combination of EN 12531 (bed castors), IEC 60601 testing on the assembled device, and hygiene features such as antimicrobial or easy-clean compounds. We supply declarations and test reports per project.
Catalogue & CAD files
Files are sent to a company email address so we can log which series you are designing in — and tell you when a revision changes.