How to Measure Your Car's Bonnet or Tailgate Gas Strut Before You Buy (UK Fitting Guide)

Whether it's a bonnet that won't stay up or a tailgate that slams down, worn gas struts are one of the most common — and easiest — car repairs you can do yourself. The hard part isn't fitting them, it's ordering the right ones. This guide walks through exactly how to measure and identify the gas struts on your car before you buy, so you get a proper fit first time.

Step 1: Identify what you're replacing

Most cars use gas struts in one or more of these locations:

• Bonnet struts — hold the bonnet open, usually a pair either side of the engine bay.
• Tailgate/boot struts — hold the boot lid or rear tailgate open.

Symptoms of worn struts are hard to miss: the bonnet or tailgate slowly sinks down on its own, doesn't stay up at all, or feels much lighter to push than it should when opening. This happens because the internal gas charge in the strut gradually leaks out over years of use — it's wear and tear, not usually a sign of anything else wrong with the car.

Step 2: Find your vehicle's exact strut

The safest way to order the correct gas strut is by your car's exact make, model, generation and body style (e.g. saloon, estate/touring, hatchback) — struts often differ between body styles of the same model, and between facelift/generation changes, even if the car looks similar. If your vehicle isn't listed in our current range, check the OEM part number stamped or printed on the old strut — this is the single most reliable way to confirm an exact match, and we're always happy to check a part number for you before you order.

Step 3: Measure the old strut (if you have it out)

If you've already removed the old strut, three measurements matter:

• Extended length: end-to-end with the strut fully open.
• Compressed length: end-to-end with the strut fully closed.
• Stroke: the difference between the two — this is how far the strut travels.

Along with the fitting type at each end:

• Eye end: a loop that fits over a pin or bolt.
• Ball socket: a socket that clips over a ball stud, typically 10mm or 13mm — check which, as they aren't interchangeable.

Step 4: Check the force rating

The force rating (in Newtons, N) determines how much lifting power the strut provides. Using a strut with too low a rating means the bonnet or tailgate won't stay up reliably; too high and it can open too fast or hard, which is uncomfortable to use and puts extra strain on the mounting points. Matching the original manufacturer's rating — either from the OEM part number or the figure printed on the old strut — is always the safest choice over guessing.

A quick safety note

Always support the bonnet or tailgate securely (a prop rod or an assistant) while removing old struts, since it will not stay open on its own once the strut is disconnected. Replace struts in pairs where the vehicle uses two, so both sides lift evenly.

We currently stock direct-fit gas struts for a growing range of BMW, Volkswagen, Fiat and Porsche models, with more vehicle coverage being added regularly. If you can't find your exact model yet or want us to confirm a match against an OEM part number, send us the details and we'll help before you order. All struts are UK stock — orders placed Monday to Sunday before 16:00 are dispatched the same day via Royal Mail or Evri.