How to choose the right castor

Get the castor wrong and you find out on the floor: a wheel that flat-spots under a load it was never rated for, a trolley that fights the operator down every aisle, a swivel that shudders at the first door threshold. Choosing well isn't complicated, but it does come down to specifics - the load, the floor, the environment, and how the thing gets moved all have a say.

So in this guide we'll walk through the anatomy of a castor in the order you'd work through it yourself: the load it has to carry, the wheel material for your floor, the bearing, how it steers and how it mounts, the compliance side, and where each choice tends to land for your industry. EHI is the Australian arm of Colson Group, the largest castor and wheel manufacturer in the world, so there's real depth behind these recommendations, from a 40kg furniture castor to a forged unit that'll take more than a tonne on its own.

If you take one thing from this, make it the load. Work out what each castor has to carry before anything else, because the wheel size, the material and the bearing all follow from that one number.

1.Start with the load

Everything starts with the load, so that's where we'll start too, and it's where the costliest mistakes get made. The instinct is to take the total weight and divide it by the number of wheels: four castors, so each one carries a quarter. On a real floor, that sum quietly lets you down. Floors are never perfectly flat, and the moment a trolley rolls over a slight dip or a door threshold, one castor lifts clear and its share of the weight drops onto the other three. Size each castor for a quarter and you've overloaded every one of them, and you usually won't know until a wheel starts flat-spotting a few weeks later.

Rather than guess at how much to allow for that, we lean on the method in our own catalogue, which sizes for the worst case directly. "Total load" means the equipment plus whatever it's carrying, so a 120kg cage stacked with 800kg of stock comes to 920kg all up. What each castor then needs to carry depends on the frame it's under:

So our 920kg cage on four wheels wants a castor rated for around 320kg apiece, which is that 35%. It only takes a minute with a pen, but it's the easiest step to skip on a busy day, and skipping it is the most common reason a castor comes back to us. The calculator below runs it for any layout and drops you straight onto the castors that meet the number.

Once you've got the figure, there's one more thing to weigh in: how the load travels. The catalogue ratings assume an average floor at walking pace, up to about 4 km/h, which is fine for anything a person pushes. Put it behind a tow tug, run it quicker than that, or let it take a shock every cycle, and you'll want some headroom on top. As a rule of thumb we add roughly half again for powered work, and double it for genuine impact duty. That part is judgement rather than a catalogue number, so if your application is sitting close to the line, it's worth a quick call before you settle on a series.

The load figure quietly settles one last thing, too: how hard the equipment is to push. The heavier the load and the smaller the wheel, the more effort it takes to get moving, and Safe Work Australia's guidance puts the sensible ceilings at around 350 N to break a load into motion and 200 N to keep it rolling. The single biggest thing you can do about that is fit a bigger wheel - rolling resistance falls off roughly in step with diameter, and a larger wheel climbs a threshold or an expansion joint with far less shove. A precision ball bearing helps too. So if push force is a worry on your job, start with wheel diameter and work back from there.

Worth being straight about the limit, though: the calculator sizes the castor, but it doesn't sign the design off. It can't see point loads, a tray stacked heavier at one end, or the side forces a tow bar feeds through a swivel. For anything heavy, powered, medical, or headed somewhere hazardous, get an engineer to confirm the choice, and lean on us as the second pair of eyes.

2.Match the wheel material to the floor, and to what's on it

Colson I3 · 250kgred urethane, the all-rounderShop this castor

With the load sorted, the next question is what the wheel is made of, and that comes down to your floor and whatever happens to be on it. This is the decision that fails slowly rather than all at once: a wheel that marks a good floor, flat-spots in the racking over a long weekend, or swells and comes apart in a washdown bay a few months in.

Nine times out of ten, the answer is polyurethane, which is why most of the range sits there. It carries a solid load, rolls without marking the floor, takes oil and water in its stride, and it's happy across the -20 to 80°C that covers most factories. When polyurethane isn't the answer, it's usually because one thing about the floor or the environment rules it out, so here is how the common materials sort themselves:

A couple of things catch people out here, and both are worth knowing before you order. Leave a polyurethane or rubber wheel parked under load for days and it'll slowly take a flat spot, so if your gear tends to sit still for long stretches, a harder nylon or hard-PU wheel will hold its shape. And it's tempting to buy more load rating by going to a wider flat tread, but a wide contact patch is a lot harder to swivel, so you can quietly hand back in operator effort what you gained in capacity.

PolyurethaneShop NylonShop RubberShop Cast ironShop PneumaticShop Puncture-freeShop

3.Match the bearing to how often, and how fast, it moves

Colson I3 · 230kgprecision bearing, total lockShop this castor

The bearing is what the castor feels like in the hand, and on a floor where people push equipment all day, that's a safety question as much as a comfort one. Three types cover almost everything we sell, and choosing between them comes down to how often, and how fast, the thing moves.

Plain (bush) bearings suit gear that mostly stays where it's put - stillages, static racking, the odd reposition. They shrug off shock and washdown, and a nylon bush needs no maintenance. They're hard work to get moving, though, so they're the wrong pick for anything someone pushes all day.

Roller bearings take heavy loads and a hard knock, at a moderate push and an occasional grease. They're a sensible middle ground for a heavy manual cart when the budget's tight.

Precision ball bearings are the ones to reach for when effort matters. Sealed for life, lightest to start and to keep rolling, and rated for the quicker pace a powered tow line runs at, up to around 10 km/h. Where push force is a concern, and under Australian WHS it usually is, this is the bearing that brings it down. Most of our castors come this way already.

4.Configuration and mounting

Colson I6 · 180kgblue rubber, swivel plateShop this castor

Two decisions are left, and both are about control rather than capacity: how the unit steers, and how the castor fixes to your frame.

Steering comes down to which castors swivel. Two fixed and two swivel tracks straight and steers from the swivel end, which is what you want for anything run down a long aisle. Four swivel goes sideways and turns on the spot, which is lovely in tight spaces, but it wanders on a straight push and it's a handful on a ramp. Four swivel with a pair of directional locks gives you both: drop the locks for the straight run, release them to crab into a corner. On anything that has to do both, it's worth the extra. For a long or heavy unit, sitting two fixed castors in the middle of six lets them carry a share of the load and hold a line, and it's worth keeping four-swivel or diamond layouts off ramps unless the castors have swivel locks, or they'll try to get away from you. It's also worth knowing why two swivel castors of the same size can feel so different to steer, and that comes down to the offset - the small gap between the pivot and the wheel's axle. That gap is what lets the wheel trail and swing round to follow you; it's built into the castor's design rather than something you pick, but it's the reason a good swivel turns sweetly where a cheap one shudders.

Brakes aren't all doing the same job, and the difference matters the moment someone leans on the equipment. A wheel brake stops the wheel but lets the castor swivel. A directional lock does the reverse, holding a straight line without stopping the wheel. A total lock stops both at once, and for anything that has to park and stay put, medical gear especially, that's the one to specify.

Mounting is the last call, and the one most often got wrong on a reorder, because it has to line up with the holes already in your frame. A top plate is the strongest and most common fixing, and it suits most fabrications. A bolt hole takes a single central bolt, a threaded or expanding stem suits tube and lighter frames, and a socket drops straight onto a matching spigot where the equipment already has one. Whichever it is, the plate size and hole centres, or the stem thread, have to match what's already there, so measure them before you order, or send us a photo and we'll match it for you.

SwivelShop FixedShop BrakedShop Plate mountShop Bolt holeShop Threaded stemShop SocketShop AccessoriesShop

5.Compliance, by environment

Colson FS · 100kgdual lock, medical & institutionalShop this castor

Most castors never have to satisfy a standard. A few environments are the exception, and in those the castor becomes part of how the finished equipment passes its own tests, so it pays to know which rule applies before you specify.

Medical and hospital equipment is governed at the equipment level by IEC 60601-1, not by any castor part number, but two of its requirements land squarely on the castor. The force to move the equipment can't exceed 200 N, measured a metre off the floor (clause 9.4.2.4.2), which points you straight at large-diameter precision-bearing castors. And it has to have wheel locks or a braking system to stop it drifting, which is why a total lock tends to be the default on anything that has to park safely.

Food, pharma and cleanroom work is about hygiene rather than a single number. The job is to design out the places bacteria can sit: stainless steel (304 for general washdown, 316 where it's saline or chemically harsh), sealed precision bearings so nothing gets in and no grease washes out, a smooth housing with no crevices or open springs, and a wheel that stands up to cleaning - thermoplastic, nylon or a good polyurethane, never cast iron or natural rubber.

Static-sensitive and explosive areas - electronics assembly, operating theatres, ATEX-classified zones - need the castor to carry static away to an earthed floor. The trade sorts this by electrical resistance: conductive at or below 10⁴ ohms, antistatic at or below 10⁷ ohms, tested to ISO 22878. In an ATEX zone it also has to be spark-free in construction, with no exposed steel or cast-iron tread that could strike a spark on the floor. We stock conductive-wheel options for this, so tell us the zone or the resistance you're working to and we'll source to it.

Australian workplaces carry a WHS duty that touches nearly every trolley on the floor. The Safe Work Australia Hazardous Manual Tasks Code of Practice makes managing high or sudden push-pull force a legal obligation. It doesn't set a hard number, since it's a risk assessment, but the figures the state regulators lean on sit around 350 N to get a load moving and 200 N to keep it going. You get under those the same way every time: a bigger wheel, a precision bearing, and a wheel no harder than the floor needs. The castor is the lever that turns a manual-handling risk into a compliant one.

Standards do get revised. We've checked the clauses and classes here against the source documents, but before you design to a specific figure, confirm the current edition for your case, or ask us and we'll confirm it with you.

6.Castors for your industry

Colson X1 · 2000kgurethane on cast iron, the heavy endShop this castor

EHI supplies right across Australian industry, and in practice the right castor shifts by trade as much as by spec. If you'd rather start from the job than the part number, find your industry below - each one lands on a starting collection.

Manufacturing & EngineeringMachine bases and workshop trolleys. Steel-cored PU or cast iron, precision bearings.Heavy duty castors Warehousing & LogisticsPickers, cages and tow lines. Larger PU wheels, precision bearings, total locks.Ball bearing castors Food & BeverageWashdown and hygiene. Stainless, sealed bearings, nylon or TPR wheels.Stainless castors Healthcare & Aged CareQuiet movement, safe parking. TPR wheels, total-lock, low push force.Medical castors Mining & ResourcesHeavy and abrasive. Super heavy duty, cast iron and pneumatic.Super heavy duty Construction & InfrastructureRough, broken ground. Pneumatic and puncture-free for kerbs and debris.Pneumatic wheels Retail & HospitalityShopfitting, display and back-of-house. Light, quiet and floor-friendly.Shopfitting castors AgricultureYards and sheds, often wet. Pneumatic and flat-free, nylon or galvanised.Puncture-free wheels

7.How to order

Over the phone

Have these to hand and it's a two-minute call:

1. Load - the total weight (gear plus what it carries), or the load per castor if you've worked it out, and how many castors.
2. Wheel diameter - in mm, or in inches if that's how your equipment's dimensioned. Bigger rolls easier.
3. Wheel material - or just tell us about the floor and what's on it, and we'll pick.
4. Bearing - or how often and how fast it moves, and we'll match it.
5. Brake - none, wheel, directional or total lock.
6. Mount - plate, bolt hole or stem, with the plate size and hole centres, or the stem thread. Measure what's there now, or send a photo.
7. Environment - washdown, chemical, heat, static, outdoor, medical. This one overrides the defaults.

On the site

All of that maps onto the filters on the castor range, so you can spec it yourself:

1. Open the castor range and set the load-capacity filter to the band the calculator gave you.
2. Add the filters that matter for the job - wheel material, diameter, bearing, brake, mount. The grid narrows to castors that meet the lot at once.
3. Open a product and read the spec: the full load rating, the wheel and bearing detail and the dimensions sit in the spec table, and the datasheet PDF is on the same page.
4. Log in for your account pricing and order, or call us for an account and pricing for your first order.

Standards reference

For the specifiers who need to cite them. We've checked these against the source documents; confirm the current edition before you design to it.

• AS 1961 series - the Australian castor standard, adopted directly from the ISO family (AS 1961.2 = ISO 22878 test methods, AS 1961.5 = ISO 22881 institutional, and so on).
• ISO 22877 to 22884 - the international set: vocabulary, test methods, and requirements by application (furniture, swivel chairs, institutional, hospital beds, and speeds up to and past 4 km/h).
• EN 12526 to 12533 - the European equivalents. Castors under these don't fall under a CE-marking directive.
• IEC 60601-1 - medical electrical equipment: the 200 N push-force limit (clause 9.4.2.4.2) and a requirement for wheel locks or a braking system to prevent unwanted movement.
• Electrostatic classes - conductive at or below 10⁴ ohms, antistatic at or below 10⁷ ohms, tested to ISO 22878 / EN 12527.

The castor brands we carry

EHI's own Easyroll range and premium Colson castors, both from the world's largest castor and wheel manufacturer.

Not sure on any of it? Send us the load, the floor and a photo of the mounting, and we'll spec the castor for you.