Hi everyone,
I have several height-adjustable bar stools like the ones shown in the attached photos, and they have developed the same problem.
The stools use a lever underneath the seat to adjust the height. When I pull the lever without sitting on the stool, the seat rises normally and can be adjusted to its maximum height. However, once I sit on it, the mechanism does not seem able to hold the pressure/height anymore.
Under my weight, the seat gradually sinks until it reaches the lowest possible position. If I stand up and operate the lever again, it rises normally, but the same thing happens as soon as I sit down.
The stools are otherwise in good condition, so I would prefer to repair them rather than replace them.
From what I understand, these stools probably use a gas-lift/pneumatic cylinder similar to an office chair, but I have never disassembled this type of mechanism.
I would appreciate some advice on:
- Is this symptom usually caused by a worn or failed gas-lift cylinder?
- Could the adjustment lever or valve mechanism be keeping the cylinder slightly open instead?
- Is there any practical way to repair/recondition the existing cylinder, or is replacement normally the only solution?
- Are these cylinders generally standardized, or would I need to measure the existing one before ordering a replacement?
- What measurements/specifications should I check to find a compatible replacement?
- How difficult is it to remove the old cylinder from the base and seat mechanism without damaging the stool?
I have several identical stools, so if the cylinders are the problem, I would ideally like to repair all of them rather than replace the entire set.
Photos attached showing the stools, adjustment lever, base and central column.
Any advice on diagnosing the problem before I start taking them apart would be very helpful.
First thing is checking they’re rated for your weight. If they are, I think the problem is not a loss of pressure because it would’ve gone soft very fast in a couple up-downs. So imo (not a specialist in pneumatic things, but I’m pretty good with machines in general) it must be the valve you move with the lever not closing properly. I have a couple chairs at work that don’t have spring-loaded levers and you have to push down them for the chair to stay at the chosen height, so try pushing the lever a bit. If it’s an outside problem—something bent or badly adjusted, dirt or something that stops the movement of the mechanism— then you might be able to fix it, but if it’s an inside problem with the valve itself, it’s worn out or gets stuck, then I’m afraid you’ll have to replace the whole piston assembly.
To answer your questions, as I said I don’t have that much experience with pneumatic parts, but parts in general are never too standard nor very custom, that is they usually are standardised but there are so many standards and specifications and variations that yours may be hard to find. Look for references/codes printed on the cylinder, the specifications you’ll need to find another one would be diameter(s), length(s), displacement, pressure/force, there could be also different kind of fastening types and ways to actuate the valve.
How hard it’s going to be, I can’t tell, but it’s most likely possible to do.