Guide
How to replace the gas lift on an office chair
The whole job takes about twenty minutes with two tools. Here is exactly how we do it, including the one step that beats most people.
If your chair sinks the moment you sit down, or will not go up at all, the gas lift has failed. Nothing else on the chair causes that exact symptom. The good news: a gas lift is a replaceable part, and swapping it is one of the more satisfying jobs in DIY.
What you need
- A replacement gas lift. Most task chairs take a standard fitting, but lengths and weight ratings vary, and some brands use their own. We stock Aeron lifts in the shop.
- A pipe wrench. A large adjustable spanner will do at a push.
- A rubber mallet.
- An old blanket or towel.
One rule before you start: never cut into or open a gas lift. The cylinder is pressurised and it is not repairable, only replaceable. Everything else in this job is low risk.
The five steps
- 1
Lay the chair on its side.
Work on the blanket. Partly for the floor, mostly because you are about to get grease on something.
- 2
Knock the base off.
The base is held on the cylinder by friction alone, no bolts anywhere. Hold the base steady and tap the bottom end of the cylinder down through the centre hole with the mallet. It lets go with a pop.
- 3
Pull the old lift out of the mechanism.
This is the step that defeats people. Years of sitting press the taper into the mechanism until it feels welded. Clamp the pipe wrench near the top of the cylinder and twist while pulling. You are not unscrewing anything, just breaking the grip. Do not worry about scratching it. It is going in the bin.
- 4
Fit the new lift.
Seat the top of the new cylinder into the mechanism, then press the base onto the bottom end.
- 5
Sit on it.
Your weight seats both joints better than any tool can. Run the chair up and down a few times and you are done.
If it is a Herman Miller Aeron
The method is the same. The part is not. Classic and Remastered Aerons use different lifts and they are not interchangeable, so check which generation you have before ordering. Size matters too, so if you are not sure whether yours is an A, B or C, our size guide shows how to check.
One thing worth doing first: if you bought the chair new, check Herman Miller's warranty. Their cover runs for twelve years and includes the pneumatic cylinder, so the fix may cost you nothing through the official route. We are independent specialists, not affiliated with Herman Miller, and we keep genuine and compatible Aeron lifts in stock.
When not to bother
Some straight talk. If the chair wobbles at the mechanism as well as sinking, or the base is cracked, the lift is only part of the story and a new one will not fix the rest. And if the chair cost four figures and you would rather not learn on it, this is one of our most common visits at desks across London. Either way, you now know what the fault is, which is most of the value.
Common questions
I replaced the lift and the chair still sinks. What now?
Either the new lift is faulty, which is rare but real with cheap ones, or the fault was in the tilt mechanism rather than the lift. If a known-good lift still sinks, suspect the mechanism.
Are gas lifts universal?
Mostly. The taper fittings are standardised on the vast majority of task chairs, but lengths, strokes and weight ratings vary, and some brands, including Herman Miller, use their own.
How long should a gas lift last?
Five to eight years of daily use is typical. They fail gradually. The chair drifts down over an hour at first, then eventually sinks the moment you sit.