What Size Gas Lift Strut Do I Need for My Trailer?
What Size Gas Lift Strut Do I Need for My Trailer? South African Sizing Guide
Correct length and Newton force rating for trailer lids, camper roofs, bakkie canopies, and ramp doors across Gauteng. 24-month warranty. Same-day dispatch available. Call +27 71 080 5429.
Trailer Gas Lift Strut Sizing, the Short Answer
The gas lift strut you need for your trailer depends on two things, the extended length and the Newton force rating. As a working rule, the extended length should sit at roughly 50% to 60% of the total length of the lid or door being lifted, and the mounting bracket should sit 20% to 25% of that length away from the hinge. Toolboxes and small hatches typically run 100N to 250N, standard luggage trailer lids sit between 350N and 500N, and pop-up camper roofs can climb past 1000N. Gas It Lift Struts matches every trailer strut to the correct length and force rating before it leaves the workshop.
Key Takeaways
- Extended length should be 50% to 60% of the lid or door length
- Mounting bracket sits 20% to 25% of that length from the hinge point
- Two struts are strongly recommended to stop the lid twisting
- Add a 1.2 to 1.5 safety margin for wind and added cargo
- Always mount rod-down to protect the internal seals
- Measure the old strut fully extended, never compressed
How to Work Out Gas Lift Strut Force for a Trailer
Getting the Newton force right matters more than most trailer owners realise. A strut that is too weak will not hold the lid up on its own, and you will find yourself propping it with a piece of wood again within a month. A strut rated too strong fights against closing, strains the hinges, and can eventually bend the frame it is mounted to. Gas It Lift Struts sees both failure modes regularly on farm trailers, camping trailers, and bakkie canopies across Gauteng, and correcting the force rating is usually the fix.
Engineers calculate the exact pressure needed per strut using a mechanical balance formula. It looks more complicated than it is in practice.
The Formula for Precise Strut Force
F = (W × 9.81 × L) ÷ (d × n) × Safety Margin
- F, force per strut in Newtons
- W, total weight of the lid or panel in kilograms
- L, distance from the hinge to the lid's centre of gravity, usually the halfway point
- d, distance from the hinge to the strut's mounting point
- n, number of struts fitted, two is highly recommended
Once the base figure is calculated, multiply by a safety margin of 1.2 to 1.5. This accounts for wind loading on an open lid and any added weight from roof racks or stored cargo, both common on Gauteng trailers that spend time on the open road.
Typical Gas Lift Strut Sizes for Common Trailer Applications
Not every job needs the full formula worked out by hand. If you would rather match your trailer to a standard size band, the table below covers the applications Gas It Lift Struts fits most often across Gauteng.
| Application | Typical Length | Typical Force Range (Per Strut) |
|---|---|---|
| Toolboxes & small hatches | 200mm – 350mm | 100N – 250N |
| Bakkie & truck canopies | 350mm – 450mm | 150N – 250N |
| Standard luggage trailer lids | 435mm – 535mm | 350N – 500N |
| Heavy camping & roof-rack lids | 535mm – 670mm | 500N – 650N |
| Pop-up caravan & camper roofs | 670mm – 1000mm | 600N – 1000N+ |
Gas lift struts belong to the wider family of gas springs, sealed nitrogen-filled cylinders used across vehicle, trailer, and industrial applications worldwide. The same sizing logic applies whether the strut is holding up a trailer lid or a machine access panel.
Fitting Rules That Protect Trailer Struts
Orientation matters as much as sizing. Gas It Lift Struts always recommends mounting rod-down, meaning the skinny piston side sits at the bottom when the lid is open. This lets the internal lubricating oil settle against the rubber seals, which stops gas leaking out and extends the strut's working life considerably.
When replacing a dead strut, pull the rod out fully by hand and measure centre-of-eyelet to centre-of-eyelet. Measuring it compressed is the single most common reason customers order the wrong length. Heavy duty struts also place serious localised pressure on their mounting points, so back thin sheet metal or fibreglass with plywood or a steel plate, and use proper steel brackets rather than self-tapping into bare panel.
Gas It Lift Struts supplies and fits gas lift struts for trailers across Gauteng, including Johannesburg, Pretoria, Centurion, Midrand, and all four Rand regions. If your existing strut has failed and you need a straightforward gas strut replacement, our team confirms the correct length and force rating over the phone before dispatch.
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Frequently Asked Questions
Common questions about what size gas lift strut to fit on a trailer.
How do I know what size gas strut I need?
Measure the fully extended length of your current strut from centre-of-eyelet to centre-of-eyelet, then match the force rating to the weight of your lid using the table above or the mechanical balance formula. Call Gas It Lift Struts with your trailer type and lid weight and we will confirm the correct length and Newton rating.
Where can I find gas struts in South Africa?
Gas It Lift Struts supplies gas lift struts across Gauteng, including Johannesburg, Pretoria, Centurion, Midrand, and all four Rand regions, with nationwide courier delivery available. Standard sizes dispatch same day, and hard-to-find applications are sourced quickly on request.
What can I use instead of gas struts?
Some trailer owners use a manual prop rod or a mechanical latch, but these lack the controlled, dampened lift a gas strut provides and carry a higher risk of the lid dropping unexpectedly. A correctly sized gas strut remains the safer, longer-lasting option for any regularly opened trailer lid.
How much weight can a gas strut lift?
This depends entirely on the strut's Newton force rating and how many struts are fitted, ranging from around 100N for a small toolbox hatch to over 1000N for a heavy pop-up camper roof. Fitting two struts rather than one is recommended for wider lids, as it shares the load and stops the panel twisting.
Need the Right Size Gas Lift Strut for Your Trailer? Call Us Today.
Speak directly to our team. We match struts to the correct length and force rating for trailers, canopies, boots, and bonnets, with same-day dispatch available.
