Which castors do I need, and how do I fit them?
Load rating, wheel material and fixing type — the three choices that decide whether something rolls easily or ruins the floor, and where a glide is the better answer.
- Difficulty
- beginner
- Time
- 30 min
- Read
- 3 min
Short answer
Add up the loaded weight, divide by the number of castors, and choose ones rated well above that — three castors carry the load when a fourth is off a bump, so allow a margin. Match the wheel to the floor: soft rubber or polyurethane on hard floors, harder wheels on carpet. Plate fixings are stronger than stem fixings.
Castors are chosen by size and appearance far more often than by rating, which is why so many end up seized, flat-spotted or dragging grit across a wooden floor. Three decisions cover almost every case, and they are worth making in order.
What you'll need
- The loaded weight of the item
- Castors or glides of the right type
- Screws or bolts to suit the plate
- A drill and a bit for stem sockets (optional)
- A square and a tape measure
Step by step
- Work out the loaded weight and divide it by the number of castors.Then allow a substantial margin, because on any uneven floor the load is carried by three castors rather than four. Under-rated castors seize, develop flats and shed their tyres.
- Choose the wheel material for the floor, not the item.Soft rubber or polyurethane tyres for hard floors — they roll quietly and do not mark. Harder nylon or polypropylene wheels for carpet, where a soft wheel simply sinks in. A hard wheel on a wooden floor will mark it.
- Choose the wheel diameter for the obstacles.Larger wheels roll over thresholds, cables and carpet edges far more easily and need less force to start moving. Small wheels look tidier and jam on everything.
- Choose swivel or fixed.Four swivel castors give full manoeuvrability and can feel unstable on a long item. Two fixed at one end and two swivel at the other tracks straight and steers, which is what a trolley wants.
- Choose the fixing type.A plate castor bolts or screws to a flat surface with four fixings and is much stronger. A stem or bolt castor pushes into a socket in a leg, which is neater and weaker. For anything heavy, use plate castors.
- Decide how many need brakes.Two braked castors diagonally opposite is usually enough to stop an item moving. A total-lock brake that stops the swivel as well is what you want on anything that must not creep.
- Fit them square and at the same height.Measure and mark from the same reference on each corner. A castor a few millimetres out makes the item rock permanently, and packing it out afterwards is awkward.
- Use bolts through, not just screws, on anything heavy.Screws into chipboard or the end grain of a leg pull out under side load. Bolts with penny washers through the base is the durable arrangement.
- Consider a glide instead where it does not have to roll.Felt pads, plastic domes, PTFE glides and adjustable levelling feet all let furniture be slid occasionally without the height, cost and floor wear of a castor.
Tips
- Castors pick up grit and hair and then grind it into the floor. On a wooden floor, clean them periodically — it is the wheels rather than the castor that damage a finish.
- Adjustable levelling feet are the answer to a rocking cabinet on an uneven floor, and they are far easier than shimming.
- Fitting castors raises the item by the castor's overall height, which matters under a worktop, in a fitted space or where the item has to pass under something.
Common mistakes
- Choosing castors by the item's empty weight — A tool chest, a kitchen island or a storage unit is several times heavier loaded. Rate for the loaded weight with a margin, or the castors seize.
- Fitting stem castors into chipboard legs — The socket works loose in the board and the castor eventually falls out. Plate castors bolted through are the right fixing for board furniture.