Replacing Gas Struts: How to Fit Replacements for LIFT-O-MAT Correctly

October 30, 2025

A gas strut assists in opening furniture flaps using compressed nitrogen gas and reliably holds them open via a specified extension force in Newtons.

When a kitchen wall unit flap no longer stays up or abruptly drops down when opened, the fitted gas strut is usually defective. Over the years, wear on the internal seals allows gas to escape, causing the cylinder pressure to drop. Replacing these components is a routine task that takes approximately 10 to 15 minutes using the correct replacement fitting and basic tools.

This guide is aimed at fitters and ambitious DIY enthusiasts, explaining the precise removal, correct selection of nominal force, and proper installation of replacement struts for the common LIFT-O-MAT system and equivalent designs.

Selecting the Correct Replacement Strut

Before beginning the replacement, ensure you have the exact matching spare part. A gas strut must never be replaced with a model of completely mismatched specifications, as this can either overload the hinges or fail to operate properly.

Checking the Extension Force in Newtons

The most crucial specification is the extension force, measured in Newtons (N). On most struts, this is printed directly on the cylinder body. Typical ratings for standard kitchen flaps range between 150 N and 400 N. Look at your old component for markings such as "200N", "250 N", or "320N".

If the marking has worn off and is no longer legible, the required force can be estimated. As a rule of thumb, 10 N corresponds to a lifting capacity of roughly 1 kg. For a 2.5 kg flap (including handle) with struts fitted on both sides, you will require two struts rated at around 125 N to 150 N each. For heavy fronts made of MDF or solid wood, dedicated Gas Struts for Heavy Flaps are used, which can provide ratings from over 400 N up to 500 N.

Checking Dimensions and Stroke

In addition to force, the dimensions must match. Measure the hole-to-hole centre distance: the distance from the centre of the upper ball socket to the centre of the lower ball socket when fully extended. Standard lengths in furniture making are frequently 245 mm or 268 mm. The stroke defines the distance the piston rod can travel into the cylinder (often between 80 mm and 90 mm). The ball studs mounted to the cabinet walls generally have a standardised diameter of 10 mm.

Distinction from Other Furniture Fittings

A technical note on terminology: a gas strut (often referred to as a gas spring) is designed primarily to lift and support loads. It must not be confused with a standard soft-close buffer. The latter only dampens the closing action of a door and provides no lifting force. Complex Flap Fittings featuring intricate linkage mechanisms and spring systems (such as bi-fold lift systems or parallel lift mechanisms) also belong to a separate category. A classic gas strut is a linear fitting typically used alongside standard concealed cup hinges (opening angles of 95° or 110°) mounted to the cabinet top panel.

Required Tools and Materials

No specialist tools are needed for this replacement. Prepare the following items:

Matching replacement struts (e.g. from the LIFT-O-MAT range or equivalent Gas Struts)
Small flat-head screwdriver (blade width 3 mm to 4 mm)
Folding rule or calliper
A second person to support the flap if necessary
Optional: New Flap Stays or ball studs if the existing brackets are bent or worn.

Step-by-Step Guide: Replacing a Gas Strut

Replacement is ideally carried out directly on the installed wall cabinet. The flap must remain open throughout the fitting process.

1. Secure the Flap

Open the cabinet flap fully. Because the old strut can no longer bear the weight, the flap must be supported. Ask a second person to hold the door in its maximum open position. If working alone, prop the flap securely against the cabinet base using a suitable piece of timber. Take care not to overextend the hinges in full overlay or inset applications.

2. Release the Retaining Clip

Examine the ends of the old strut. The ball socket sits over a ball stud screwed into the cabinet side panel. This connection is secured by a small metal spring clip. The metal clip acts as a collar encircling the ball head to prevent it slipping off. Slide the blade of your flat-head screwdriver underneath this clip. Gently lever the clip outwards by approximately 2 mm to 3 mm. It does not need to be removed completely; lifting it slightly is sufficient to release the lock.

3. Pull Off the Old Strut

While holding the clip open, pull the strut socket sideways off the ball stud with a firm tug. Repeat this step at the opposite end of the strut. Remove the defective part. Now inspect the ball studs on the cabinet: are the fixing screws still secure in the wood? If the screw holes in the chipboard have stripped, the brackets must be repositioned or re-anchored into the System 32 hole pattern using wood glue and dowels before installing new parts.

4. Check the Mounting Orientation of the New Strut

Before installing the new component from the Silver Gas Struts range (or another matching finish), check the correct mounting orientation. In most applications, the strut is fitted with the thicker cylinder pointing upwards (attached to the flap) and the thinner piston rod pointing downwards (attached to the cabinet side). This orientation ensures internal oil lubricates the piston rod seals and allows the end-position damping to operate smoothly as it opens.

5. Push the New Strut into Place

Installing the new strut is considerably easier than removal. The retaining clips on new ball sockets generally do not need to be prised open with a screwdriver. Align the socket squarely over the ball stud and press the end firmly with your thumb. A distinct "click" indicates that the clip has snapped over the ball and locked into place. Attach the flap side first, followed by the cabinet wall bracket.

6. Functional Check and Fine Adjustment

Once both struts have been fitted (always replace them in pairs!), remove the support prop and test the movement. The flap should open almost automatically past a certain angle and remain securely in its fully open position. When closing, slight resistance should be felt. If the flap does not sit flush when closed, adjust the alignment using the concealed hinge mounting plates to true up the gaps.

Common Installation Mistakes

Although the mechanical replacement is straightforward, several common mistakes can significantly reduce the service life of new fittings.

Choosing the wrong force rating: Fitting a 380 N strut to a lightweight MDF flap will make it extremely difficult to close. The continuous strain can eventually pull the hinge screws out of the chipboard. Conversely, an under-specified strut (e.g. 150 N on a solid wood front) will fail to keep the flap open.
Replacing only one strut: Gas springs wear out at a similar rate. When the left strut fails, the right strut is usually also depleted of pressure. Replacing only one side creates uneven load distribution, causing the flap to twist over time.
Scratching the piston rod: Never grip the bare piston rod with pliers or sharp tools. Even microscopic scratches on the metal surface will damage the internal cylinder seal during compression, causing gas to escape rapidly.
Ignoring worn hinges: The strut provides lifting force, but the concealed cup hinges guide the door. If the hinges are worn or loose, even the strongest strut will not operate correctly. Always check that the hinges are firmly fixed.

Applications Beyond the Kitchen

Gas struts are not limited to overhead kitchen units. Adapted versions with different stroke lengths and significantly higher Newton ratings are used on storage chests, toy boxes, and ottomans. Wardrobes also utilise linear assistance mechanisms, such as a Wardrobe Lift, which dampens the descent of the hanging rail and assists when lifting it back up. The underlying physical principles of load distribution and leverage remain identical.

FAQ – Frequently Asked Questions

Can I repair or refill a defective gas strut? No. The cylinders are pressurised to high levels (sometimes exceeding 150 bar) and are permanently sealed during manufacture. Opening them is hazardous. Defective struts must be properly disposed of and replaced as a complete unit.

What happens if I combine struts with different Newton ratings? This results in asymmetrical force. Over time, the cabinet flap will twist, panel alignment will be lost, and the hinges on the heavier-loaded side will wear prematurely. Always install two identical struts.

Why can I not compress the new strut by hand before fitting? This is entirely normal. A strut rated at 250 N requires approximately 25 kg of force to move the piston rod. Without the leverage provided by the fitted cabinet flap, compressing it by hand is virtually impossible. Do not attempt to force it down against the floor, as this can bend the piston rod.

How long does a new furniture gas strut last? When fitted correctly and subject to typical use (roughly 5 to 10 opening cycles per day), high-quality fittings generally last around 5 to 8 years. Extreme temperature fluctuations or permanent overloading can shorten this lifespan.