How to Choose Gas Struts for a Truck Bed Tonneau Cover
Why Do Tonneau Covers Need Gas Struts?
Gas struts hold a truck bed tonneau cover open at a fixed angle so it doesn’t slam shut or crush your hands while you’re loading cargo, and they control the descent when you close it.
Hard folding and hinged tonneau covers are heavy — often 40-70 lbs depending on material and bed length — and without a strut (or a pair of struts) they either drop shut under their own weight or need to be manually propped, which most manufacturers specifically warn against because a slipped prop can cause serious injury.
What Force Rating Do I Need for a Tonneau Cover?
Most single-panel and tri-fold tonneau covers use struts rated between 100N and 250N per strut, with heavier fibreglass or aluminium covers needing the higher end of that range.
- Soft roll-up covers: Rarely need struts at all — the frame is usually light enough to lift by hand.
- Tri-fold and bi-fold hard covers: Typically 100N-150N per strut, mounted in pairs.
- One-piece hinged hard covers: Often 150N-250N per strut, again in pairs, since the whole panel lifts as one unit.
- Aluminium retractable covers: Force needs vary widely by mechanism — check the manufacturer’s fitting guide rather than guessing.
Undersizing the strut means the cover won’t stay up on its own. Oversizing makes it fly open too fast and strain the hinges. Matching the rated force to the panel weight and hinge geometry is the whole job — see our gas spring force calculator if you’re working from panel weight rather than an existing part number.
How Do I Measure for a Replacement Tonneau Strut?
Measure the strut’s extended length end-to-end, then measure compressed length, and note the stroke (the difference between the two) alongside the end fitting type at each end.
- With the cover open and the strut at full extension, measure eye-to-eye (ball socket to ball socket, or eye to eye if it uses bracket mounts).
- Push the strut closed by hand (or measure a failed one that’s already compressed) and record that length.
- Subtract compressed from extended length to get the stroke.
- Check whether each end uses a ball socket, eyelet, or bracket mount — the two ends aren’t always the same.
For general measuring technique that applies across vehicle applications, our gas strut measuring guide covers the same process in more depth.
Should I Replace Both Struts at Once?
Yes — replace both struts on a tonneau cover as a pair, even if only one has failed.
Struts that were fitted at the same time wear at a similar rate. If one has lost pressure enough to notice, the other is usually not far behind, and running mismatched force ratings on either side of a cover causes it to lift unevenly and puts uneven strain on the hinges. This is the same logic that applies to liftgate struts and cabinet doors — see our guide on telling if your struts are bad for the symptoms to check before you decide.
