Gas Strut Too Weak or Too Strong? Size the Force, Length and Fit

A lid that drops on your head, a hatch that won’t stay shut, or a strut that sags on frosty mornings usually means the wrong force or length, the cold, or lost gas. Size it by force in newtons, extended length and stroke, then fit it rod down.

PartsForMachines stocks 271 products in its gas struts range, from 6mm to 20mm rod struts made by Metrol to the end fittings, brackets and locking tubes that mount them.

New Struts Won’t Hold the Lid, or It Won’t Shut: What Force Do I Need?

Work it out from the lid’s leverage about the hinge, not its weight alone. Multiply the weight by the distance from the hinge to the lid’s centre of gravity. Divide that by the strut’s lever arm (the distance from the hinge to the strut’s centre line), then by the number of struts. Allow roughly 10N for every kilogram.

So where the struts mount matters as much as the strut itself. If you can’t pin the figure down, a variable force strut gives you room: the NS-V-10-200 variable force gas strut spans 70–1200N, carries 25–140kg per balanced pair, and arrives set to maximum force unless you ask otherwise.

Can I Just Fit a Standard Size? Measuring Extended Length and Stroke

Yes, as long as it matches your old strut’s extended length and stroke. Measure the old one fully extended, from the centre of one end fitting to the centre of the other, then fully closed; the stroke is the difference between the two. Match those first, then rod size and force.

Our struts are listed by stroke and extended length. The NS-V-8-250 gas strut, for example, has a 250mm stroke, extends to 550mm and covers 50–650N on an 8mm rod. Rods run from 6mm to 20mm, and the force ranges climb with rod size.

Strut Sagging in Cold Weather: Will It Recover, or Replace It Now?

It may well recover. Gas pressure, and with it force, falls as the temperature drops, by roughly 3.5% for every 10°C, and returns as it warms up. A strut that barely held in summer can sag on a frosty morning.

If it also sags on a warm day, it has probably lost gas past the seal and needs replacing. Push struts such as the NS-V-10-200 are rated from −30°C to +80°C. On plant, grit and scratches on the rod wear that seal, so a matching protection tube, such as the MPT-10-200 for that strut, is worth fitting, even on a strut already in service.

Rod Up or Rod Down? Fitting a Gas Strut the Right Way Round

Rod down, for a standard push strut, ideally when the panel is closed. With the body uppermost, the oil inside keeps the rod seal wet and damps the end of the stroke. Fitted rod up, the seal sits out of the oil and can fail early.

Support the panel before you unclip the old strut, as an unsupported lid can fall. Where you can, fit ball joints, as side loads on the rod wear the seal unevenly.

What Should I Check Before I Order?

• extended length and stroke, measured centre to centre on the old strut
• force in newtons per strut, or the lid weight and hinge-to-centre-of-gravity distance so we can help
• rod size and thread: M6 for 6mm and 8mm rods, M8 for 10mm, M10 for 14mm, M14 for 20mm
• the end fitting and bracket at each end, with an opposite-hand bracket where the layout is mirrored
• where it works: damp, coastal or wash-down sites suit a 316 stainless strut with stainless fittings

Browse the gas struts range, or contact the PartsForMachines team by WhatsApp, telephone or email with your measurements and a photo of the old strut.

Product options, delivery options and returns terms are shown on each product page. A 30-day return policy applies to eligible items.

Frequently Asked Questions

What does the N figure on a gas strut mean?

It is the strut’s force in newtons: how hard it pushes. Roughly 10N supports 1kg, before you allow for the hinge leverage. A variable force strut is sold with a force range, such as 50–650N, and set within it.

Can I reduce the force of a strut that is too strong?

Not on a fixed-force strut, which must never be opened, so fit the correct one instead. Variable force struts such as the NS-V-14-200 can be bled down, releasing a little gas at a time until the lid balances.

How long should a gas strut last?

It depends on use and conditions. Gas slowly escapes past the rod seal over time, and scratches, paint, dirt and side loads on the rod damage that seal faster, so keep the rod clean and never paint it.

Is it safe to work under a lid held only by gas struts?

Not without a back-up where a falling lid could hurt someone, as struts lose pressure over time. A locking tube such as the MLT-10-200 self-locks over an NS-V-10-200 at full extension and releases by hand.

Should I replace both struts if only one has failed?

Usually, yes. The lid’s force is shared between the struts, so both should have the same stroke, extended length and force. A new strut paired with one that has lost gas will not share the load evenly.

Ball joint, eye, clevis or rose eye: which end fitting do I need?

A ball joint swivels freely, an eye hinges on one pin, a clevis pins in line and a rose eye takes up slight misalignment. Match the thread to the rod: the B5 ball joint end fitting has an M6 thread for 6 or 8mm rods.

Will a stainless strut fit where my steel one was?

Usually, if the stroke and extended length match. Allow an extra 5mm of body length on a 316 stainless strut such as the NS-SS-V-10-200, and use stainless end fittings and brackets so the whole mounting resists rust.

What is a traction (pull-type) gas strut for?

It pulls its rod in rather than pushing it out, so it can hold a hatch shut, draw a cover against its frame or stop a linkage drifting. The NS-V-TR-10-200, for example, works between 300mm closed and 500mm open.

How do I dispose of an old gas strut safely?

Never heat it. Clamp it upright, rod down and fully extended, wear goggles and ear defenders, and drill a 3mm hole about 20mm from the tube end. Drain the oil, then recycle the metal under local regulations.