A desk chair that slowly drops while you sit in it almost always has a gas cylinder whose seal has failed, and the fix is a new cylinder. Before you buy one, rule out the seat mechanism, because a misadjusted set screw or lever can make a good cylinder sink, rise on its own or refuse to move. A chair that wobbles, leans or creaks has a different problem; see how to fix desk chair rocking or looseness .
Confirm the cylinder is the problem
The gas lift is the vertical cylinder between the seat mechanism and the five-star base. It holds height with pressurized gas behind a seal, and a button on top releases it when you pull the height lever.
A simple check: mark the seat height, sit still for a few minutes, and look again. A slow, steady drift downward points to a leaking seal. There is no published industry threshold for how much drop counts as failure; as a rule of thumb, if you can see the seat has moved within a short sitting session, the cylinder is not holding.
| Symptom | Likely cause | What to do first |
|---|---|---|
| Seat sinks while you sit | Failed cylinder seal | Replace the cylinder |
| Seat sinks, especially right after a cylinder swap | Set screw in the mechanism pressing the cylinder button | Back the set screw out with a hex key |
| Seat rises on its own | Set screw or activation adjustment holding the button down | Adjust the set screw before replacing anything |
| Lever does nothing | Disconnected or bent lever linkage, or loose seat bolts | Inspect the underside of the seat |
| Chair wobbles or leans | Broken mechanism weld, worn cylinder bushing, damaged base or caster | Inspect those parts; a new cylinder only helps if the bushing is the cause |
The set screw causes are documented by both a parts supplier and a chair maker. Chairpartsonline’s symptom checker lists a set screw above the cylinder as the cause of a chair that goes up on its own, or sinks after a cylinder replacement. Steelcase’s Leap instructions say a chair that rises by itself, sinks with an occupant, or will not move when the lever is lifted may simply have its cylinder adjustment screw out of position, and give the steps to reset it.
Check the warranty before you buy parts
A failed cylinder may be a warranty repair. Steelcase, for example, says it will repair or replace covered parts that fail under normal use. Find the model number (usually on a label under the seat) and check with the maker or dealer first. Brand chairs may also need a brand-specific cylinder: parts suppliers sell separate cylinders for some Steelcase and Herman Miller models, and later Steelcase Leap chairs use a cylinder button that must line up with the handle bracket.
A stopgap if you need the chair today
A hose clamp tightened on the exposed piston rod, or a length of PVC pipe slit lengthwise and snapped over it, stops the seat from sinking below that point. Chair maker Merryfair describes both methods and notes the catch: either one freezes the chair at a single height. Set the height first using OSHA’s guidance : the whole sole of your foot on the floor, with the back of the knee slightly higher than the seat.
Measure for the right replacement
Most office chairs use a standard cylinder, and suppliers make matching easy:
- Taper. The top taper on current standard cylinders is stamped “TYP 17-4”. Chairpartsonline describes that as the standard top taper for chairs made after about 2000, and flags older 17-2 and 17-26 tapers as obsolete: those chairs need a new mechanism and cylinder together.
- Diameter. If the outer column is 2 inches (50 mm) across, it is a standard cylinder. The piston rod on a standard cylinder is about 1.1 inches (28 mm).
- Travel (stroke). Measure the seat height with the seat all the way down and all the way up. The difference is the travel. Pick a replacement with similar travel unless you want to change your height range.
- Length. Compare the replacement’s column length and extended length with the old one so the new seat range still fits your desk. Caford Castors measures from the underside of the mechanism to the underside of the base, at the lowest and highest settings.
- Class. Cylinders are stamped with a strength class such as Class 3 or Class 4. It does not affect fit, but it does relate to the user weight the cylinder is certified for. See Class 3 vs Class 4 gas lifts .
Remove and install the cylinder
The cylinder is held by friction tapers at both ends, not threads, so removal takes force. Steelcase’s instructions for its Leap, Gesture and Think chairs follow the same pattern:
- Raise the seat to its highest position, then lay the chair on its side or upside down.
- Separate the base by hitting the bottom of the cylinder with a hammer while pulling the base away. Hit the outer rim of the cylinder, never the inner rod.
- Free the cylinder from the seat mechanism. Steelcase uses a dedicated removal tool struck with a hammer. If the joint will not let go, spray WD-40 where the cylinder enters the mechanism, wait about 20 minutes and try again. A pipe wrench twisted on the cylinder also works, but Steelcase notes it ruins the cylinder, so use it only on the old one.
- Push the new cylinder into the mechanism and tap it firmly with a rubber mallet. Fit the base onto the bottom and tap the base with the mallet.
- Turn the chair upright and sit in it. Your weight seats both tapers.
Herman Miller’s Aeron disassembly instructions use the same idea: a nylon cap and hammer to drive the cylinder out of the base.
Never open, drill, cut or heat a cylinder. Gas spring maker Stabilus describes its pressurized products as potentially dangerous and specifies a clamped, eye-protected procedure for depressurizing them before disposal, warning that metal shavings and oil can spray out. Ask your local waste service how it accepts old cylinders.
Repair or replace the chair
A new cylinder is worth it when the rest of the chair is sound: the base is not cracked, the mechanism is tight, the seat plate is secure and the chair still fits you and your desk. Replace the chair instead when:
- the base is cracked, flexes, or lets the cylinder lean;
- the mechanism is loose or has a broken weld;
- the sinking arrives along with flattened foam, a loose seat or other worn parts;
- the chair has an obsolete taper, a hidden or integrated cylinder, or a brand part you cannot get.
OSHA’s chair guidance calls for a strong five-legged base, so a damaged base is not a part to work around. After any repair, add the chair to a monthly maintenance check , and if a caster is the next thing to go, see how to fix loose desk chair wheels .
FAQ
Can a desk chair gas lift be refilled?
No. The gas lift is a sealed, pressurized part. Gas spring makers treat opening one as a controlled disposal procedure, not a repair, so replace the cylinder instead.
Why does my chair rise but not lower?
Check the lever and mechanism first. A set screw or activation adjustment in the seat mechanism can press or miss the cylinder’s release button. If the linkage works and the seat still will not move, the cylinder is the likely fault.
Can I use a pipe or hose clamp to stop my chair from sinking?
Yes, as a stopgap. A hose clamp or a slit length of PVC pipe on the exposed piston rod stops the seat from dropping, but it locks the chair at one height and does not repair the cylinder.
Is it worth replacing a gas lift on an older chair?
Yes, when the base, mechanism and seat are sound and the chair still fits you. Replace the whole chair when the sinking comes with a cracked base, a loose or broken mechanism, or other worn parts.
Sources
- Steelcase 462 Leap Task Chair and Stool Pneumatic Cylinder Adjustment/Replacement (PDF)
- Steelcase Pneumatic Cylinder Removal Tool instructions (PDF)
- Steelcase 442 Gesture Chair and Stool Cylinder Replacement (PDF)
- Steelcase 465 Think Chair and Stool Cylinder Replacement (PDF)
- Herman Miller New Aeron Task Chair and Work Stool: Disassembly for Recycling (PDF)
- Steelcase warranty overview
- Chairpartsonline: Symptom Checker
- Chairpartsonline: Understanding Cylinder Stamping
- Chairpartsonline: Is My Cylinder “Standard”?
- Chairpartsonline: Determine Cylinder Travel
- Chairpartsonline: Office Chair Gas Lift Cylinder S6111 specifications
- Caford Castors: How to Measure an Office Chair Gas Lift
- Merryfair: Office Chair Keeps Sinking? How to Diagnose and Fix It
- Stabilus: Disassembly and pressure discharge of Stabilus products prior to disposal (PDF)
- OSHA Computer Workstations eTool: Chairs
Sources checked October 3, 2026.
See Also
If you want to move from general advice into actual product choices, start with Desk Chair Maintenance Checklist: What to Check Every Month, Why Your Desk Chair Squeaks and How to Fix It, and How to Set Up a Standing Desk Accessory Layout.
For a wider picture after the basics, Tilt Lock vs Tilt Limiter on Office Chairs and Best Ergonomic Office Chairs of 2026 are the next places to read.