New chair casters make a chair in a home office or other workspace feel like new. When your office chair casters don't roll quite right, they may just need any hair, fibers or dirt cleared from around the wheels. Caster wheels that have snapped, however, need to be replaced. If you can operate a screwdriver, the task is within your reach.
Turn the office chair upside down on a desk or sturdy table, and check for carpet thread or fibers caught in the wheel axle. This can be removed with needle-nose pliers, and a sharp knife or scissors. If this solves the problem, give all the axles a drop or two of lubricating oil, and return the chair to use
For a damaged caster, removal is needed. Try to pull out the bad caster. Gripping with a glove or towel will help. If it's really stuck, use a regular screwdriver to pry the post or stem out of its socket. Work the end of the screwdriver blade in a little at a time, prying at different points around the stem of the wheel.
As the stem starts to back out, lay the screwdriver sideways in the widening gap, and pry both ways against the socket edge. This allows you to lever even more of the stem out of the socket. Keep pulling as you pry, until the caster pops out.
Find replacement office chair casters online, or at your local home center. Caster wheels are designed to roll best on different floor surfaces. If you're replacing a set of wheels, choose a type to match the surface of your work area. To replace a single bad caster, find the best match to the remaining wheels.
Install the new caster into the socket, and push it in as far as possible. It will seat itself in place, pretty much whenever you do, with your weight helping the stem click into place.