Elevator Wire Rope Tension Imbalance: Causes, Risks, and Prevention

Steel wire ropes are critical components in an elevator traction system. They carry the full load of the car, passengers, and cargo, so steel wire rope tension directly affects traction reliability, ride comfort, and—most importantly—passenger safety. This article explains what happens when elevator steel wire rope tension becomes uneven, why it occurs, and how to prevent it.

1) Why Uneven Steel Wire Rope Tension Is Dangerous

Take a traction elevator with 4 suspension/traction ropes as an example. If 3 ropes are tight and 1 rope is relatively loose, the system may look normal from a distance, but in reality:

• Only the tight ropes carry most of the load

• The loose rope “floats” and contributes little to load sharing

• The tight ropes create higher contact stress in the traction sheave grooves

1.1 Accelerated Rope and Sheave Wear

Over time, the heavily loaded ropes wear faster, their diameter reduces, and they become more likely to develop broken wires or strand damage. At the same time, the traction sheave grooves wear unevenly. In severe cases, you can visibly see different groove depths where ropes sit deeper or shallower.

1.2 Speed Mismatch and “Rope Creeping” (Slip in Grooves)

When a rope sits deeper in a groove, the effective groove radius R is smaller, so its linear speed is slightly slower. If another rope sits shallower, its linear speed is slightly faster.

But the elevator must travel the same distance as a unit. That mismatch can cause ropes to micro-slip forward/backward in the grooves—often described as “rope creeping” or “rope shifting”. Results include:

• Car vibration and noticeable “jerk” or shock feeling

• Higher friction in the groove → higher heat and wear

• Wear increases slip, and slip increases wear: a self-reinforcing vicious cycle

• In extreme cases, ropes and the traction sheave may need early replacement

2) Main Causes of Elevator Steel Wire Rope Tension Imbalance

2.1 New Elevator Installation Problems

Cause A: Rope tightness not set evenly at installation
If installers rely on hand feel or visual checks (instead of a tension gauge) and then run the elevator on slow speed, each rope can develop different structural elongation.

Cause B: Adjusting too late
If tension is only adjusted after a period of running, the ropes that were tight will already have stretched structurally, while the loose rope has not fully “taken up” its structural elongation. This creates a gap that is hard to correct later.

Cause C: Limited adjustment range at rope ends
Rope end terminations often allow only limited adjustment travel (e.g., around a few hundred millimeters). If the initial tension difference is large, the available adjustment may be insufficient to restore balance.

Cause D: Partial roping during installation
If only some ropes are installed and the elevator is run before all ropes are hung, the early-installed ropes experience elongation that the later ropes do not. When all ropes are finally installed, tension differences can be too large to eliminate.

2.2 Replacing Ropes on Existing Elevators

(1) Replacing Only 1–2 Ropes

This is one of the most common reasons for persistent steel wire rope tension issues.

• New ropes may differ in brand, material, construction, and elasticity from the old ropes

• New ropes still have structural elongation to develop

• Old ropes have already “settled” and stretched in service

Even if you tighten the new rope(s) during installation, after running for a period the new ropes elongate and become looser again—making it nearly impossible to match tension with the remaining old ropes. The new ropes may then carry little load, wear quickly, and increase uneven sheave groove wear.

(2) “Slow-Run Replacement” One Rope at a Time

Replacing one rope, running slowly, then replacing the next rope creates different elongation histories between ropes. Even if the tension is initially set evenly, the ropes quickly become uneven in operation.

(3) Residual Twist and Internal Stress Not Released

During installation, internal torsional stress should be released as much as possible. If not, ropes may twist or roll slightly in the grooves, increasing wear and worsening tension imbalance.

3) How to Prevent Uneven Wire Rope Tension (Best Practices)

3.1 Use Qualified, High-Quality Ropes

Choose factory-certified elevator traction ropes with stable construction and good flexibility. Better rope flexibility helps the rope conform in the groove, reduces abnormal wear, and improves load sharing.

3.2 Handle and Hang Ropes Correctly (No Twist, No Kinks)

When paying out and hanging ropes:

• Do not twist, kink, knot, deform, or allow strand loosening

• Let the ropes hang naturally to help release internal stress before final tensioning

• Avoid installing in a way that “locks in” torsion

This helps ropes remain soft and round, increasing groove contact area and reducing twisting wear.

3.3 Keep Rope-End Components Consistent

When installing or replacing rope-end devices (springs, buffers, pads, terminations):

• Use the same type, same batch when possible

• Ensure springs/pads have the same elastic characteristics and original length

• If components differ in specification, replace them as a complete set to maintain consistency

3.4 Measure Tension Properly and Re-Adjust Repeatedly

Steel wire rope tension can change after initial operation due to groove compression, load changes, and rope elasticity. One adjustment is often not enough.

Recommended approach:

• Use a proper rope tension gauge

• Measure each rope, calculate the average, and adjust repeatedly

• Aim to keep each rope within ±5% of the average tension, and as close as possible

3.5 Improve Traction Sheave Groove Accuracy and Materials

Uneven groove geometry can create tension differences and speed mismatch. Good manufacturing and maintenance practices include:

• High groove machining accuracy

• Consistent pitch diameter across grooves

• Quality material/heat treatment for wear resistance

Better groove precision improves load distribution and reduces the chance of rope creeping.

3.6 Consider Groove Liners (Sheave Inserts) Where Appropriate

Using groove liners (especially with good elasticity) can:

• Cushion minor groove diameter differences

• Reduce micro-slip caused by small pitch errors

• Improve traction conditions and extend rope/sheave life

• Reduce sheave maintenance costs in suitable applications

3.7 Rope Specification Control (Quality Checks)

For new ropes, common quality expectations include:

• Stable tensile strength range suitable for traction elevator use

• Consistent diameter, good roundness, small diameter tolerance

Consistent rope geometry supports stable traction and more uniform tension sharing.

4) Quick Checklist for Maintenance Teams

• Measure elevator steel wire rope tension with a gauge (not by hand)

• Adjust tension iteratively until within target tolerance

• Avoid replacing only 1–2 ropes (prefer full-set replacement)

• Prevent twist/kink during installation and let ropes hang to release stress

• Inspect sheave grooves for uneven wear depth and rope seating differences

• Monitor for vibration/jerk symptoms that may indicate rope creeping