Changzhou LongXiang Gas Spring Co.,Ltd

Replacing or specifying a gas spring becomes much easier when the measurements are recorded correctly. Three values are especially important: extended length, stroke and extension force. A small error can prevent a lid from opening fully, create interference in the closed position or overload hinges and brackets.

What Information Is Needed?

Before removing the old unit, record the application, mounting orientation, number of gas springs and all markings on the cylinder. Photograph both end fittings and the installed geometry. Then measure the gas spring and the equipment mounting points.

1. Measure the Extended Length

Extended length is normally measured from the center of one mounting connection to the center of the other while the gas spring is fully extended. For ball sockets, measure ball-center to ball-center. For eyelets, measure between hole centers. For clevis fittings, use the mounting-pin centerline.

Do not measure only the cylinder or exposed rod. End fittings are part of the installed length. If the spring cannot extend freely while installed, remove it safely before measuring.

2. Measure the Stroke

Stroke is the distance the piston rod travels from fully extended to fully compressed. When both center-to-center lengths are known:

Stroke = Extended length − Compressed length

Never force an unknown gas spring closed with a clamp or vise. It may contain high pressure. If compressed length cannot be measured safely, use the visible rod travel, original specification or manufacturer identification.

3. Identify Extension Force

Gas spring force is commonly stated in newtons (N). Markings such as 500N or 800N normally indicate nominal extension force. Approximately, 100 N equals 10.2 kgf or 22.5 lbf.

Required force is not the same as lid weight because mounting geometry creates leverage. A heavy panel may need moderate spring force with a long moment arm, while a lighter panel may require more force when the spring acts close to the hinge.

A Simple Force Calculation

For an early estimate, balance turning moments around the hinge:

Total gas spring force × effective spring arm ≈ lid weight force × center-of-gravity arm

If two gas springs share the load, divide the total force between them. Spring angle, changing geometry, friction and desired opening behavior must also be considered. The formula is a starting point, not a substitute for motion analysis and prototype testing.

Measure Mounting Geometry

• Measure from the hinge to the moving-side mounting point.

• Measure from the hinge to the fixed-side mounting point.

• Record closed and fully open lid angles.

• Check clearance around the cylinder, rod and fittings.

• Confirm the spring will not bottom out before the lid closes.

Keep a small travel margin at both ends. Using the gas spring as a mechanical stop can overload the piston, fittings and brackets.

Check Rod, Cylinder and Fittings

Measure rod and cylinder diameters with calipers without scratching the rod. Also record thread sizes, hole diameters, ball-stud diameters and the orientation of angled fittings. These details help identify the product series and compatible end connections.

Installation Details That Affect Service Life

Gas springs are commonly mounted with the piston rod pointing downward in the normal operating position. This helps lubricate the seal and supports consistent damping. Avoid side loading, bent brackets and misaligned ball studs.

Temperature also affects force. For outdoor, heated or refrigerated equipment, provide minimum and maximum temperatures. See our guide to gas spring temperature effects.

Replacement Measurement Checklist

• Extended center-to-center length

• Compressed length or stroke

• Nominal force in newtons

• Rod and cylinder diameters

• End fitting types and thread sizes

• Number of springs per lid

• Lid weight, dimensions and center of gravity

• Open and closed mounting positions

• Operating temperature and environment

Frequently Asked Questions

Can I choose a replacement using length alone?

No. A replacement must also match stroke, force, end fittings, geometry and environmental requirements.

Where is gas spring length measured?

It is generally measured center-to-center between the two mounting connections, not from the ends of the cylinder body.

Should I install a stronger gas spring for safety?

Not automatically. Excess force can make a panel difficult to close and overload hardware. Select force from load and geometry, then verify it on the equipment.

Get Selection Support

Accurate measurements reduce replacement time and improve operating safety. Browse our gas spring products or contact LongXiang with photos, dimensions and force markings for selection support.