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Castors and Trolley Wheels: Load, Wheel Material and Brakes
A castor is chosen by four numbers and one habit. The numbers are the load, the wheel diameter, the mounting pattern and the floor; the habit is counting how many castors actually carry the load, which is almost never all of them at once. Get those right and a trolley rolls easily for years; get them wrong and the wheels flat-spot, the bracket bends, or the whole thing shudders across every joint in the floor. This guide covers the castor types in this range and how to match them to a load.
Load, wheel and floor
- Divide by three, not four. On an uneven floor a four-castor trolley often carries on three wheels, so each castor should be rated for at least a third of the total load.
- Bigger wheels roll over obstacles. Wheel diameter decides whether a castor crosses a cable, a threshold or a drain grating or stops dead at it.
- Hard wheels roll easily, soft wheels protect floors. Nylon is hard, low-friction and noisy; polypropylene is lighter and kinder to a soft floor.
- Swivel or fixed. Swivel castors steer, fixed castors track. A trolley needs both, usually two fixed and two swivel.
- Brakes stop the trolley, not the load. A braked castor holds a stationary trolley; it is not a substitute for chocking a heavy load on a slope.
| Castor | Best for | Note |
|---|---|---|
| Plate-mounted castor | General trolleys and equipment | Fixed, swivel and braked in one range |
| Industrial trolley castor | Heavy loads on hard floors | Larger wheels, higher load rating |
| Levelling support castor | Machines and benches that must sit level | Adjustable height, load spread over a foot |
Plate-mounted castors
Plate-mounted castors in fixed, swivel and braked versions, in PP or nylon from 3 to 8 inch cover the widest range of jobs, because the plate is the standard way to attach a castor to a wooden or steel frame and the range offers the three functions a trolley needs. A practical layout is two fixed castors at the back and two swivel castors at the front: the fixed pair keeps the trolley tracking in a straight line when it is pushed, and the swivel pair does the steering. Fit four swivel castors only where the trolley has to move sideways, because a trolley with four swivels is harder to push in a straight line and can run away on a slope. Wheel size should be chosen by the worst surface the trolley will meet, not the best: a 3 inch nylon wheel is fine on a smooth workshop floor and hopeless on gravel.
Heavy loads and equipment that has to sit level
A heavy-duty industrial trolley castor in 4 to 8 inch is built for the load case where a general castor fails: a machine, a pallet truck conversion, a rack that is rolled rather than lifted. The bracket is thicker, the wheel is wider and the bearing is a proper roller rather than a plain bush, which is what stops the castor from flat-spotting after months of standing under a static load. Fit these where the trolley is pushed rather than steered around furniture, and keep to hard floors, because a wide hard wheel on a soft floor has high rolling resistance and marks the surface. A levelling adjustable support caster in the GD-40 to GD-150 range, with fixed and swivel options solves a different problem: the equipment has to be moved and then levelled, so the castor combines a wheel with an adjustable foot. Raise the foot and the machine rolls on the wheel; lower the foot and the weight comes off the wheel and onto a levelling pad, which takes the load off the castor and lets the machine sit flat. That is the right choice for a machine tool, a bench or a conveyor section, because an uneven machine chips cutters and shakes fixings loose.
Fitting and keeping them rolling
- Match the plate to the frame. Check the hole centres and the plate size before ordering, and reinforce a thin frame with a plate on the far side.
- Keep the swivel clear. Swarf, grit and string around the swivel race is what makes a castor stop turning and start dragging.
- Lubricate the swivel, not the wheel. The bearing in the swivel is the part that wears; a sealed wheel bearing needs nothing.
- Look for flat spots. A castor left under a static load for months develops a flat and then thumps on every revolution.
- Do not exceed the rating. A castor overloaded once is a castor that is permanently deformed, and it will fail later without warning.
- Chock a loaded trolley. Brakes hold a stationary trolley on the level; they are not a parking system for a slope.
Frequently asked questions
How do I work out the load per castor?
Take the total weight of the trolley and its load, add a margin for shock and uneven floors, and divide by three rather than four. Then choose a castor rated above that figure.
Two fixed and two swivel, or all four swivel?
Two and two for a trolley pushed in a straight line, which is most trolleys. Four swivels only where the trolley has to move sideways or turn in its own length.
Why does my trolley shake?
A flat-spotted wheel, a damaged swivel race, a hard wheel on a rough floor, or a castor that has been overloaded. Inspect one wheel at a time, since a single bad castor makes the whole trolley shake.
Nylon or polypropylene wheels?
Nylon for hard floors and heavy loads, because it rolls easily and resists abrasion. PP for lighter loads and soft floors, where a hard wheel would mark the surface.
Can I use a support castor as a normal castor?
It rolls, but the wheel is small and the castor is designed for levelling rather than transport. Use it to reposition equipment, then lower the foot and let it stand on the pad.
Where to start
Browse the full castors range, or the wider hardware accessories category for clamps, fittings, pulleys and nozzles. Tell us the load, the floor and how the trolley has to move, and we will point you at the castor that fits.
