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Help Selecting The Correct Gas Strut.

Article by CaravansPlus - Caravans Plus

Gas struts or springs are used in caravans and RVs for helping to lift and hold heavy things like the roof of a pop-top or an island beds for storage.

There are many types of Gas Struts and it is important to use the right one. This is a quick guide to help you choose.

How Are Struts Measured?

The main things that vary between the Struts are the Strength, the Extended Length, and the Compressed Length. Other things that may be a choice are the Shaft size and the Ball Joint size. The most commonly used ball joint on RV's are 10mm.

On this website we name our Struts with a format like:
Gas Strut, 525mm > 305mm, 350N, 8mm Shaft with 10mm Ball Joint Ends.

In this case the
Extended Length = 525mm
Compressed Length = 305mm (Extended - Stroke)
Strength = 350N (which is about 35kg)

Selecting The Correct Gas Strut

How To Install.

In the below example the uncompressed strut is 130mm. The position of the fixed end is around 130mm from the hinge point.

If the strut can compress by 50mm then the moving end can be mounted up to 50mm from the hinge. The further away from the hinge point the less it will open but the push will be stronger.

How To Change Ball Joints.

Circlip on Ball Joint

Ball joints and brackets of the same size are interchangeable. Sometimes your gas struts may be delivered from us with the ball joint pre-installed into the socket.

We are often asked how to remove the ball from the socket to enable the use of the brackets we offer. There can be black plastic ends with a metal surround that needs to opened or the spring steel retaining clip that is holding the ball firmly in place.

Carefully use a small prying tool. A small flat blade screw driver works best as you can twist the blade to remove the clip easily.

How To Work Out What Strength You Need.

If you are replacing an existing strut the strength (N) should be printed on the strut you have. Otherwise...

The easiest way to guess the lifting weight required for a gas strut, is to use a set of bathroom scales, and length of timber.

Pick the position where you think the gas strut will be located and place the timber and scales there. This will show you the weight that is being applied in that position. If for example the scales read 20kgs then you need at least a 200N (20kgs x 10) strut to hold the weight.

Remember to take into consideration any extra weight such as a mattress.
It is important to select the correct length of strut that will open to the desired height, but also allow the stroke to fully close.

Selecting The Correct Gas Strut

Advanced: The Scientific Method.

For those who would like to try a more mathematical approach to working out the strength then please study the formulas presented.

F1 = G x XG
F2 = A x F1 x LS

Z = length of lid from pivot (hinge) point in millimetres.
XG = Centre of Gravity in millimetres.
G = The weight of the lid in Newtons. 1Kg is 9.8N (Round this to 10 Newtons).
LS = Radius of Gas Spring Force in millimetres.
A = Number of gas springs per application. We recommend using two for most applications such as island beds

Selecting The Correct Gas Strut

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  • comment-avatar


    I want to add 2 gas struts to my 2013 A Liner roof but don't know what length or strength to use I hope you can help me.

  • comment-avatar


    what size struts to lift roof coromal mirage roof 396 mod

  • comment-avatar


    Hi Kevin, my Jayco ones had a serial number on them which provided the right lift strength

  • comment-avatar

    Steven Butcher

    I am a vehicle builder by trade. Usually just buy the replacement for the part without much thought. This site is extremely helpful as I am now fitting struts to tool trailers that have very heavy steel doors 1800 long x 900 wide. doors physically lifted up toopen position by han and a steel rod "prop" put in to position. Very unsafe to remove rod and then lower by hand. Knowing how to calculate which strut is going to lift and hold the weight is very helpful.

  • comment-avatar


    Hi there, Hope you can help, please... new to gas struts... recently purchased 2 x 350N struts for a special project at home (to crazy to explain!!). The struts seem to be jammed open and I can't compress them at all. 2 questions : 1/ Can a 100kg guy compress a 350N strut or is the strut to powerful? 2/ If I stick the struts in the fridge will this cool the gas (and thus reduce pressure) so that then the strut can be compressed somewhat? Will look forward to your answers, if possible, thanks again, Geoffrey.

  • comment-avatar

    George Drew

    Hi Geoffrey - please don't freeze them! If you can't compress the struts with gentle hand pressure, your lid, or whatever you are trying to lift) is too light. Follow the formula on this website, and you will get a better idea. WARNING: Please don't mess with gas struts - they are very powerful and can cause serious injury. If you try to compress them incorrectly, you can also blow the seals rendering them useless. Cheers.

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