Repair before you replace
Replacement castors, wheels and components. A chair that rolls badly, sinks, or scratches the floor is usually a five pound part away from being fine, and replacing the whole chair is a waste of a working frame.
Measure the stem before you order
Castor fittings are not universal. The stem is the pin that pushes into the chair base, and diameters vary between ranges. Pull one castor out, measure the pin, and match that rather than assuming.
Most office chairs use an 11mm stem, but plenty do not, and a castor that nearly fits will work loose within weeks.
Hard floor or carpet
This is the choice people get wrong. Hard castors are for carpet; soft castors are for hard floors. It feels backwards, but a hard wheel on laminate scratches it and rolls away from you, while a soft wheel on carpet drags.
If a chair keeps rolling when someone stands up, or gouges the floor, the castors are wrong for the surface rather than faulty.
What is not worth repairing
A failed gas lift on a cheap chair, and any cracked base. Both are load-bearing safety parts, and by the time one has failed the rest of the chair is usually at the same age.
If a chair is genuinely worn out, our task and operator chairs cover replacements, and heavy duty models last longer where the failures keep repeating.