What Are Lift Supports and When Should You Replace Them?

What Are Lift Supports and How Do They Function?

Lift supports are self-contained, nitrogen-charged gas springs designed to provide consistent lifting force and velocity damping for lids.

Lift supports, often referred to as gas struts or gas springs, function by using compressed nitrogen gas to exert constant outward pressure on a piston rod. This force assists in lifting and holding heavy panels, such as car boots, bonnets, or industrial access hatches, in an open position. Unlike mechanical springs, these units provide a controlled force curve and use internal hydraulic oil to dampen movement, preventing erratic or slamming motions.

Why Do Lift Supports Use Nitrogen Gas?

Nitrogen gas provides a stable, compressible medium that maintains consistent force while resisting internal corrosion within the steel cylinder.

Nitrogen is inert and non-flammable, making it the ideal medium for pressurized cylinders. It does not react with the internal seals or the hydraulic oil required for damping. Because nitrogen is a gas, it is highly compressible, allowing the strut to store potential energy and release it smoothly across the entire stroke length.

How Is Lifting Force Measured in Newtons?

Lifting force is measured in Newtons at a 20-degree Celsius mid-stroke point to standardize performance ratings across all industry manufacturers.

The Newton (N) rating indicates the force the strut can exert when in a static or mid-stroke position. You should use our Gas Spring Force Calculator to determine if your replacement struts align with the weight requirements of your specific application. Using a strut with an incorrect Newton rating can lead to either a failure to hold the lid open or dangerous opening speeds.

What Role Does Internal Oil Play?

Internal hydraulic oil provides speed-sensitive damping that prevents the strut from reaching the end of its stroke with excessive force.

As the piston travels, oil is forced through a small orifice, creating resistance. This process ensures that when you open a heavy tailgate, the strut decelerates near the end of the movement. Without this oil-based damping, the hardware would strike the frame hard, causing structural stress.

How Do I Identify When Lift Supports Fail?

Lift supports fail when they lose internal gas pressure, resulting in a lid that drifts down, slams shut, or requires manual force to hold.

Why Does My Boot or Lid Drift Closed?

Drifting occurs when the internal nitrogen charge has depleted enough that the strut cannot overcome the weight of the panel consistently.

Gradual pressure loss is a natural side effect of the seal aging over several years. Once the internal pressure falls below the threshold required to hold the static weight of the panel, the lid will slowly descend. You can find more details on troubleshooting these issues in our Gas Strut Diagnosis Guide.

Can Road Salt and Corrosion Cause Failure?

Corrosion pits the chrome rod surface, which shreds the internal seal and allows high-pressure nitrogen gas to escape the cylinder body.

In UK and coastal climates, road spray and salt quickly degrade the rod finish. Once the smooth chrome surface is compromised, the seal can no longer hold pressure. In these environments, I always recommend 316-grade stainless steel units to prevent premature failure.

How Do I Properly Select Replacement Supports?

Selecting replacements requires matching the extended length, stroke, force rating, and end fitting style of the original components.

Should I Replace Supports in Pairs?

Replacing lift supports in pairs ensures uniform force application and prevents asymmetric stress on hinges and pivot points of the panel.

Even if one strut appears to be functioning, it is essentially at the same end-of-life stage as the failed unit. I strongly advise replacing both at once. If you are uncertain about the specific model needed for your vehicle, check our Gas Strut Replacement Finder for vehicle-specific data.

Why Is Extended Length Critical?

Extended length determines the full opening angle; incorrect lengths cause the lid to open too wide or not enough, damaging the hinges.

Measuring from the center of one end fitting to the center of the other while fully extended is the only accurate way to verify the size. Never assume that the body length alone defines the travel capacity of the strut.

Frequently Asked Questions

Can I recharge a gas strut?

Gas struts are factory-sealed units that cannot be recharged or repaired; once internal pressure is lost, the assembly must be replaced.

What temperature affects lift supports?

Nitrogen pressure decreases in cold weather, potentially reducing strut force by 15% in freezing temperatures compared to 20-degree heat.

Are all end fittings universal?

End fittings are not universal; you must match your existing ball socket, clevis, or eyelet diameter to ensure a secure mounting fitment.