Key takeaways
- Using a PVC pipe or hose clamp as a lock. Both crack or slip, and pipe shards can jam the mechanism.
- Buying a cylinder by chair brand instead of by measurement. Stroke length and extended length are what matter; brand is irrelevant on standard tapers.
- Prying the base off with a screwdriver in the hub. It gouges the taper and the new cylinder will wobble.
- Hitting the cylinder body with a metal hammer. Dents lock the inner column.
- Trying to open or repressurize the cylinder. It is a sealed unit; there is nothing serviceable inside.
- Installing the new cylinder without sitting to seat it. A loose taper wobbles and eventually damages the hub.
- Choosing a Class 3 cylinder for a chair used by someone over 250 pounds. Step up to Class 4.
- Continuing to use a sinking chair for months. Repeated bottoming out compresses the cone into the base, which makes removal far harder.
A sinking office chair is one of the most annoying failures in a home office, and one of the most commonly fixed the wrong way. People jam a PVC pipe over the cylinder, which locks the height but cracks under load and leaves plastic shards in the mechanism. They spray lubricant into the cylinder, which does nothing because the failure is a lost gas seal, not friction. They buy a replacement cylinder without measuring, and it arrives 2 inches too short or with a base cone that does not fit. Or they keep sitting on the sinking chair for months, which pounds the cylinder’s cone into the base and makes it nearly impossible to remove later.
The fix is straightforward and takes 15 to 45 minutes. You have two options: a $12 to $15 clamp that locks the cylinder at one fixed height, which is fast and works if you never change your seat height, or a $25 to $40 replacement cylinder that restores full adjustment. Both are covered below, along with how to get the old cylinder out, which is the only genuinely difficult step.
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What You Need
| Item | Why | Optional? |
|---|---|---|
| Tape measure | To measure cylinder length, stroke, and diameter before buying a replacement | No |
| Replacement gas cylinder (Class 3 or 4, matched stroke) | Restores full height adjustment; typical stroke 2.2 to 5 in, $25 to $40 | Not if using a clamp |
| Cylinder lock clamp | Fixes the chair at one height without removing the cylinder; $12 to $15 | Not if replacing |
| Rubber mallet or a hammer with a wood block | Knocks the old cylinder out of the base and mechanism | No for replacement |
| Pipe wrench or large adjustable wrench, 12 in or larger | Grips and twists a stuck cylinder free of the base | Recommended |
| Penetrating oil | Loosens a cylinder cone seized in the base after years of use | Optional |
| Old towel or rag | Protects the seat and floor and gives grip on the cylinder | No |
| Phillips screwdriver or hex key | To remove the mechanism from the seat if the cylinder will not separate | Optional |
| Work gloves | Cylinder edges and base spokes are sharp | Recommended |
Step-by-Step
1. Confirm the cylinder is the problem (2 minutes)
Sit, pull the height lever, and let go. If the chair drops slowly over minutes or hours, the gas seal has failed. If it drops instantly and fully when you sit, same conclusion. If the lever does nothing at all and the chair is stuck at one height, the mechanism’s release pin may be the fault instead; check that the lever actually pushes the small pin at the top of the cylinder before buying anything.
2. Measure the cylinder (3 minutes)
Raise the chair fully and measure from the top of the base cone to the bottom of the mechanism; that is the extended length. Lower it fully and measure again; the difference is the stroke, commonly 2.2, 3, 4, or 5 inches. Measure the outer diameter of the visible column, usually 1.1 inches at the top and 2 inches for the outer sleeve. Note whether the mechanism-side cone is the standard taper, which fits nearly all chairs made in the last 20 years. Replacement cylinders such as the MySit 2.2 inch stroke model are sold by stroke length; matching yours keeps your seat height range identical.
3. Decide: clamp or replace (1 minute)
A clamp like the Salbree Chair Hero, around $14, tightens around the exposed cylinder at your chosen height and stops it dropping. Installation takes 5 minutes with no disassembly, but the chair is locked at that height permanently unless you move the clamp. A replacement cylinder at $25 to $40 takes 20 to 40 minutes and restores full adjustment. If you share the chair or change height between sitting tasks, replace. If you sit at one height and want to be done today, clamp.
4. Clamp method: set and lock (5 minutes)
Raise the chair to your working height while standing beside it and holding the lever. Slide the clamp onto the exposed inner column just above the outer sleeve. Tighten the screws evenly with the included hex key until the clamp cannot rotate by hand. Sit down; the outer sleeve now rests against the clamp instead of sliding up. Check after a day and retighten a quarter turn if it has crept.
5. Replacement method: separate the base (5 to 15 minutes)
Flip the chair upside down on a towel. Wrap a rag around the cylinder just above the base and grip it with the pipe wrench. Hold the base with your other hand or foot and twist the cylinder back and forth while pulling up. It is a taper fit, not a thread; movement in either direction loosens it. If it will not budge, strike the top of the base hub around the cylinder with the mallet, working around the circle, then twist again. For a seized cylinder, apply penetrating oil where the cone meets the hub, wait 15 minutes, and repeat.
6. Separate the cylinder from the mechanism (5 to 10 minutes)
With the base off, set the chair on its side. Wrap the rag around the top of the cylinder, just below the mechanism, and tap the mechanism housing next to the cylinder with the mallet from alternating sides. The taper releases with a pop after a few strikes. If it resists, unbolt the mechanism from the seat with the four screws so you can lay the mechanism flat and strike more cleanly. Never hit the cylinder itself; it dents and jams.
7. Install the new cylinder (3 minutes)
Slide the new cylinder’s narrow cone into the mechanism and the wide end into the base. Set the chair upright and sit down firmly two or three times; body weight seats both tapers. No hammering is needed. Confirm the height lever depresses the pin on the new cylinder and that the chair rises when unloaded.
8. Test and adjust (3 minutes)
Raise and lower the chair through its full range five times. It should rise smoothly in about 1 to 2 seconds with no one on it and hold any height under load for at least a full day. Set your working height: feet flat, knees at about 90 degrees, thighs level, typically 17 to 21 inches from floor to seat top.
Mistakes to Avoid
- Using a PVC pipe or hose clamp as a lock. Both crack or slip, and pipe shards can jam the mechanism.
- Buying a cylinder by chair brand instead of by measurement. Stroke length and extended length are what matter; brand is irrelevant on standard tapers.
- Prying the base off with a screwdriver in the hub. It gouges the taper and the new cylinder will wobble.
- Hitting the cylinder body with a metal hammer. Dents lock the inner column.
- Trying to open or repressurize the cylinder. It is a sealed unit; there is nothing serviceable inside.
- Installing the new cylinder without sitting to seat it. A loose taper wobbles and eventually damages the hub.
- Choosing a Class 3 cylinder for a chair used by someone over 250 pounds. Step up to Class 4.
- Continuing to use a sinking chair for months. Repeated bottoming out compresses the cone into the base, which makes removal far harder.
How Often
A gas cylinder is a wear part with a typical life of 5 to 10 years, or roughly 50,000 to 100,000 height cycles on a quality Class 3 or 4 unit. Cheaper cylinders on chairs under $100 often fail in 2 to 4 years. There is no maintenance that extends cylinder life; keep the exposed column free of grit and avoid dropping into the chair from standing, which spikes pressure on the seal. Check the chair once a year by setting it at full height, sitting for a minute, standing, and measuring the seat height again; more than a quarter inch of drop means the seal is going and you have a few months before it sinks fully.
When to Call a Pro or Replace
Office chairs are rarely serviced professionally because a replacement cylinder costs less than an hour of labor. Call the manufacturer instead if the chair is under warranty, since most cover the cylinder for 1 to 5 years and will ship one free. Replace the whole chair rather than the cylinder when the base hub is cracked or the taper is gouged, when the mechanism’s release lever is also broken, when the seat foam has collapsed and the casters are shot, or when the chair cost under $80 and is more than 4 years old. A chair that sinks and also rocks or clicks under load likely has a worn mechanism plate, which is a $40 to $60 part that pushes total repair cost past the value of a budget chair. In 2026 a sound mid-range replacement chair starts at $100 to $130, so weigh two $30 parts against that.
FAQ
Why does my office chair sink when I sit down?
The gas cylinder’s internal seal has worn out and can no longer hold pressure under load. It is not a lubrication problem and cannot be repaired; the cylinder must be locked with a clamp or replaced.
Are office chair cylinders universal?
Nearly. Almost all chairs use the same standard taper at both ends, so any replacement cylinder fits if the stroke and extended length match yours. Exceptions are some very old chairs and a few high-end brands with proprietary mechanisms.
How long does a replacement cylinder take to install?
Twenty to 40 minutes for most people. Removing the old cylinder from the base is the only hard part and can take 15 minutes if it has been seized by years of use. Installing the new one takes under 5 minutes.
Is a cylinder clamp a permanent fix?
It is durable, but it locks the chair at one height. Clamps hold indefinitely if tightened properly and checked after the first day. If you need to adjust height for different tasks or users, a replacement cylinder is the better fix.
