Traction Elevators in Practice – Sheaves & Ropes
By Torsten Fuka, CEO of Rudolf Fuka GmbH
There’s a situation I’ve seen again and again in traction elevator systems — and it almost always starts with the same sentence:
“The traction sheave must be defective. One groove is severely worn, the others still look fine.”
It’s an understandable conclusion. The traction sheave is a central, safety-relevant component, and visible groove wear can quickly feel like a serious reliability — or even safety — issue.
However, years of field experience have shown that in most cases this kind of uneven groove wear is not caused by a material or manufacturing defect. Much more often, it is a symptom of uneven load distribution within the rope set — typically driven by unequal rope tensions.
That’s why my first question is always the same: Have the rope tensions been measured?
The following observations are based on recurring field cases and closely align with well-known mechanisms described in industry literature.
A typical pattern: one groove worn much more than the others
In the field, the first clue is usually visual. You look at the traction sheave — and one groove immediately catches your attention: deeper, shinier, and clearly more worn than the rest. Sometimes there is metal dust nearby, sometimes the operator mentions noise or vibration, and sometimes the system still runs smoothly despite the alarming appearance. This is exactly why the pattern triggers concern: it doesn’t look random — it looks specific.
It is therefore easy to assume that the groove material or manufacturing quality must be the cause. However, this interpretation often overlooks a much more common mechanism — one that does not begin at the traction sheave, but within the rope set itself.
If the sheave material were truly the root cause, the wear pattern would usually look different: several grooves would be affected, the wear would appear more random, or there would be additional damage indicators such as cracking or spalling. When only one groove is consistently affected, while adjacent grooves remain comparatively normal, the more likely explanation is not a defective groove, but an uneven operating condition.
In practice, this almost always means one thing: The load is not being shared equally across the ropes.
The real cause: unequal rope tensions
Rope sets are designed to share the load — but only if the individual rope tensions remain close to each other. Once one rope runs significantly tighter than the others, it will inevitably carry more load and begin to dominate traction behavior.
That’s why many maintenance guidelines refer to a simple rule of thumb: the highest rope tension should not exceed the lowest by more than about ten percent.
Once that range is exceeded, uneven groove wear is no longer a surprise — it becomes a predictable outcome.
What happens when rope tensions are uneven
When rope tensions are uneven, the system begins to behave asymmetrically — and the wear pattern follows. The most highly tensioned rope carries more load, contact pressure increases, and wear in its groove accelerates.
The lower-tension ropes, by contrast, can lose traction and begin to slip. This generates additional abrasion, heat, and often fine metal dust.
The critical point is that this process tends to reinforce itself. Once one groove becomes deeper, the rope seats differently, contact geometry changes, and load distribution shifts further. Uneven tension creates uneven wear — and once wear is uneven, the imbalance usually grows faster.
How tension imbalances develop
In most real-world cases, tension imbalance is not caused by one dramatic mistake — it develops gradually. Small differences during installation may remain unnoticed at first, but they grow as ropes settle and elongate during the run-in period — especially if re-tensioning is not performed afterward.
Over time, even slight variations in operating conditions — alignment, rope path geometry, friction behavior, lubrication — can widen the spread further. That is why rope tension should not be treated as a one-time setting, but as a parameter that needs to be checked and maintained as part of routine service.
Why this matters for owners and operators
For owners and operators, uneven groove wear is rarely “just a cosmetic issue.” Even if the system continues to run, localized wear typically shortens the life of both the ropes and the traction components and increases the risk of unplanned downtime.
In many cases, the bigger cost is not the sheave or the rope set — it is the uncertainty: repeated site visits, disruptions, and the inevitable discussions about who is responsible. That is why rope-tension balance should be viewed as a reliability parameter — not as a one-time installation step.
A practical field checklist (simple but effective)
If there is one recurring lesson from these cases, it is this: rope-tension measurement should be the first diagnostic step — not the last.
When uneven groove wear appears, rope tensions should be measured first — before parts are ordered, before conclusions are drawn, and certainly before responsibility is assigned.
During installation
The rope set should be equalized as precisely as possible, and tension values should be measured and documented rather than estimated. As a practical benchmark, the deviation between the highest and lowest rope tension should remain within roughly ten percent.
After the run-in period
Because ropes settle and elongate during initial operation, tension should be re-checked after the run-in period and corrected if necessary. This step is often overlooked, yet it plays a decisive role in preventing the wear pattern from developing in the first place.
During routine maintenance
Finally, periodic tension checks should be treated as part of normal service practice. If indicators such as metal dust, vibration, or rope bounce appear, tensions should be verified immediately — because once uneven wear has begun, the imbalance tends to accelerate.
A note of appreciation — and a recommendation
This topic resurfaced recently in a conversation with Nicola Imbimbo — widely known in our industry as “Nic the Elevator Guy” — as part of Hyperion-Let’s Talk Elevators-Podcast.
Nicola has also captured many of the practical fundamentals behind traction, ropes, and real-world system behavior in his book NicTheElevatorGuy – Introductory Handbook for the Aspiring Elevator Engineer which I can recommend as a valuable reference for anyone working with suspension means and traction systems.
Let’s compare experiences
How often do you measure rope tensions in multi-rope systems in the field? Do you document values during installation and maintenance?
And have you ever encountered cases where an assumed “traction sheave defect” ultimately turned out to be a tension imbalance?
In the end, the groove rarely tells the full story — the rope tensions do.
I very much welcome comments, additions, or comparable topics — here via the contact form or on social media.
Torsten Fuka
