Replacing Gas Struts: The Right Replacement for Nobilia Kitchen Flap Doors
A faulty gas strut in a kitchen flap door loses its internal pressure over the years and must be replaced with a spare part of identical force in Newtons (N) as well as the exact same installation length.
Wall units with upward-opening front panels are standard equipment in modern kitchens, such as those from Nobilia. The fitted flap fittings ensure that the front swings up smoothly and remains reliably held in the open position. When the flap suddenly drops on its own or can only be pushed upwards with great effort, the fault almost always lies with the gas strut. This article explains technical diagnosis, selecting the exact matching replacement part, and professional component replacement.
Symptoms and Causes: Why Kitchen Flap Doors Fail to Hold
A gas strut consists of a sealed cylinder filled with high-pressure nitrogen gas, along with a piston rod. When closing the flap, the piston rod is pushed into the cylinder, compressing the gas. When opening, the gas expands and pushes the piston rod out – raising the flap.
Pressure escapes gradually over the years, much like air from an old bicycle tyre. The seals inside the cylinder are subject to natural mechanical wear and tear. Temperature fluctuations in the kitchen, constant load, and the dead weight of the front panel accelerate this process. As soon as the internal pressure drops below a critical threshold, the force in Newtons is no longer sufficient to hold the weight of the flap against gravity. The front sinks. On heavy front panels made of MDF or solid timber, this effect becomes noticeably apparent faster than on lightweight melamine fronts.
Finding the Right Replacement: Newtons (N) and Installation Length
A universal flap fitting does not exist. Selecting the replacement part strictly depends on the specifications of the old strut. Two parameters are essential here:
1. Spring Force in Newtons (N)
The force of the gas spring is specified in Newtons. This value is usually printed directly onto the cylinder of the defective strut (for example `250 N`, `320 N`, or `380 N`). The force must match the weight of the flap precisely. If a strut with insufficient force is installed, the flap will not stay open. If too strong a strut is chosen, the wall unit can barely be closed, or the enormous tensile force will eventually tear the hinges out of the chipboard.
2. Installation Length (Stroke and Overall Length)
The second criterion is the length of the strut. Measurement is taken in the fully extended state from the centre of one ball head to the centre of the other ball head (hole-to-hole distance). Common dimensions for kitchen wall units range between `245 mm` and `270 mm`. The stroke refers to the pure travel distance of the piston rod.
For wide and heavy fronts that generate high torque, specialised gas struts for heavy flap doors are used, which in some cases deliver over `400 N` and feature reinforced ball joints.
Tools Required for the Replacement
Changing the struts on a wall cabinet requires no specialist tools. The following items are needed:
- Small flat-blade screwdriver (blade width approx. `3 mm`)
- Cloth for cleaning the ball studs
- A second person or a telescopic support rod to secure the open flap
Step-by-Step Guide: Replacing Gas Struts
Replacement is a pure push-fit assembly, as the actual mountings (the ball studs) remain screwed into the carcase and the front panel.
Step 1: Secure the Flap
As soon as the first strut is unclipped, the flap will fall down unchecked. A second person must hold the front at its maximum opening angle. Alternatively, the flap can be fixed in place with a suitable support rod.
Step 2: Release the Retaining Clip
At the ends of the strut are the socket heads that sit on the cabinet ball studs. These are secured against slipping off by a small metal clip (retaining spring). Slide the flat-blade screwdriver under this metal clip and lever it slightly outwards (approx. `2 mm` to `3 mm`). The clip does not need to be removed completely; lifting it slightly is sufficient to release the lock.
Step 3: Pull Off the Defective Strut
With the clip raised, pull the socket head sideways off the ball stud. Repeat the process on the other side of the strut. Clean the exposed ball studs on the carcase and front panel using a dry cloth to remove old grease and dust.
Step 4: Push on the New Strut
Fitting the new strut requires no tools. The cylinder end (the thicker component) is usually mounted at the top on the carcase side, while the thin piston rod attaches at the bottom on the front panel. Simply press the socket heads of the new strut firmly onto the ball studs until they audibly snap into place. The retaining clip does not need to be lifted when pushing on – it expands automatically and springs back into the locked position.
Step 5: Functional Test
Repeat the process on the other side of the cabinet. Afterwards, close the flap carefully and check the gap alignment as well as the holding force in the open position.
Checking Interaction with Concealed Cup Hinges
A flap fitting always operates as a system alongside the top hinges holding the front to the cabinet carcase. If the flap binds during closing or rests unevenly, the issue is often not down to the struts, but to worn hinges.
Upward-opening flap doors generally use standard hinges with an opening angle of `110°`. If the hinge mechanism becomes worn, the geometry of the flap changes, leading to increased lateral load on the gas struts. In this case, the hinges should be inspected at the same time and replaced if there is play in the joint. For standard flaps, concealed cup hinges / cabinet hinges 110 degrees are suitable.
If the flap should also brake gently upon closing, it is worth checking the fitted hinges. If they do not have integrated damping, the front will hit the carcase with an audible bang. Upgrading to concealed cup hinges / cabinet hinges with damping (Soft Close) can be beneficial here. Pay attention to the correct mounting type (usually full overlay for surface-mounted flaps) and the cup diameter of `35 mm`. To review the full range of mounting solutions for wall units, the main category concealed cup hinges / cabinet hinges provides technical specifications across all overlay types.
Prevention: Minimising Wear on Flap Fittings
The service life of gas struts can be extended through proper operation. Cylinder seals are damaged if the flap is pulled down forcefully. The mechanism is designed to guide the closing process smoothly. Pull the front gently and let its own weight combined with the damping do the work. Additionally, keep the ball joints free from dirt and debris to prevent the piston rod from binding.
Frequently Asked Questions (FAQ)
Do both gas struts always need to be replaced at the same time? Yes. Even if only one strut seems to be defective, the second strut has already lost pressure. Replacing only one side causes asymmetric force distribution. The flap will warp, gap alignment becomes uneven, and both the hinges and the new strut will wear out extremely quickly due to uneven loading.
Can a gas strut be repaired or refilled? No. The cylinders are under high pressure. Opening the cylinder poses a serious danger to life. Once pressure has escaped, the component is irreparable and must be disposed of properly and replaced with a new part.
What happens if I install a 380 N strut instead of the original 250 N? The flap will be held extremely firmly in the open position, but will be very difficult to close. The constant high counter-pressure presses permanently against the front panel. This causes the screws of the concealed cup hinges to tear out of the chipboard or causes the front to bow. The Newton rating must match the original exactly.
How do I measure the installation length correctly? Measure the strut only when it is removed and fully extended. The measurement is taken from the exact centre of the eyelet on one ball head to the centre of the eyelet on the other ball head. A deviation of `2 mm` to `3 mm` can usually be accommodated by the tolerance of the ball studs on the carcase.