Cable & Wire Rope Stretch

Wire Rope Stretch

In any tensioned system, cable and wire rope stretch is a natural part of performance — and understanding how it works helps ensure your application functions safely and reliably.

There are two main types of wire rope stretch you should be aware of:

Structural Stretch

Structural stretch is the initial elongation that occurs as the internal strands and wires adjust under load. It’s caused by the tightening of the cable’s lay (the pattern in which wires are twisted), and is most noticeable during the first few uses.

• Structural stretch is usually less than 1% of the total cable length.
  
• This type of stretch can be minimized or completely removed by pre-stretching the wire rope prior to use — a service we can provide on request.

This pre-conditioning ensures better performance and consistency, especially in applications like control cables, rigging systems, or load-bearing slings.

Elastic Stretch

Elastic stretch refers to the actual, physical elongation of the steel wires themselves when placed under tension — similar to how a metal spring stretches under load.

Elastic stretch is reversible (the cable returns to its original length when the load is removed) and can be estimated using this formula:

Stretch (inches) = W×GD2\text{Stretch (inches)} = \frac{{W \times G}}{{D^2}}Stretch (inches) = D2W×G​

Where:

• W = Working load (in pounds)
  
• G = Cable length (in inches)
  
• D = Cable diameter (in inches)
  

This formula gives you a general idea of how much elongation to expect during normal use.

Minimizing Stretch in Your Application

• Choose a stiffer construction like 7×7 for minimal elongation under load.
  
• Consider pre-stretched cable for systems requiring high precision or repeatable movement.
  
• Always size your wire rope to allow for a working load limit (WLL) well below its breaking strength, using an appropriate safety factor.

If you’re unsure how cable stretch will impact your setup — especially in lifting, tensioning, or control systems — we’re happy to help calculate it and recommend the best solution for your needs.

Stretch Comparison by Cable Construction

Here’s a visual comparison chart showing estimated elastic and structural stretch for common wire rope constructions (7×7 and 7×19, galvanized and stainless). It helps highlight how stretch characteristics vary slightly based on construction type — useful when recommending cable for precision or load-sensitive applications.