By now, the benefits of using modern synthetic winch rope are well known in the off-road world. Besides being much lighter than steel wire rope, it's also safer for vehicle recovery use. Many ropes are made from Dyneema High Modulus Polyethylene (HMPE) fiber, a high-strength, low-stretch synthetic fiber that actually floats in water. With all recovery items, some purposeful practices can ensure your gear will last reliably for a long time.
To begin with, synthetic winch rope should be carefully spooled onto your winch drum the first time. Warn instructs owners to wind the first 10 turns or so onto your drum, then wind the remaining length of rope onto the drum under tension by winching the vehicle across flat ground. It's important to wind the rope on in this manner without leaving gaps between winds. This will keep the rope from later cutting between winds into a lower layer, which can cause issues when trying to unspool the line.
We spoke to Bill Fronzaglia of Dyneema, and he commented that the most common causes of synthetic fiber failure are due to cuts and abrasions, or extreme shock loading. By far, the worst enemy of a synthetic winch rope is abrasion, whether that's rubbing across some sharp piece of metal on your rig or dragging across rock or sand while winching. Use of a protective outer sheath can help resist abrasion where the rope might otherwise come in contact with a sharp or rough surface.
When your rope gets especially dirty, it can make good sense to clean it in a bucket of water with some mild soap to clean the fibers of dirt that can internally abrade the rope, slowly grinding the rope material. As a matter of fact, some mining companies regularly wash and clean their synthetic ropes as a maintenance procedure. However, if your rope spends most of its time just sitting on your winch spool, the degradation from dirt ingress into the fiber is rather insignificant compared to cuts or abrasion damage it may suffer.
Additionally, despite what you may have heard about synthetic rope degrading due to UV light or sunlight exposure, there is little to worry about for probably a decade or more. Terry Crump at Samson Ropes informed us that Dyneema fiber is very stable and UV degradation is minimal over time. Most companies that take fibers and manufacture ropes will coat them in colors for branding purposes or some abrasion protection. Over time the coloration may fade, but this usually has little effect on the actual rope strength. Moisture also has little effect on rope strength. Most chemicals do not affect rope integrity and quality ropes are often tested to aviation chemical exposure test standards.
Should a synthetic line break in the field, it's possible to remake an end loop or splice two ends relatively easily. Knots should be avoided, if possible, as these connections offer breaking strength of maybe only half that of the rope itself. Proper splices are the way to go for rope break repairs.
One of the common ways a synthetic rope can become damaged is at the winch fairlead. First, ensure there are no metal burrs or sharp edges that might come in contact with the rope. Second, make sure the backside of your fairlead (most commonly a Hawse) is smoothly radiused where the rope will ride. Lastly, make sure the steel fairlead opening on your winch plate has a large opening (like the one shown here) to ensure there is no way the rope can come in contact with the steel winch plate bracket.
As mentioned, the biggest vulnerability of synthetic winch rope is damage due to abrasion. It's wise to run a protective sheath over your winch rope. These are generally 6 to 10 feet long and can be slid along your line to whatever location is needed. A rope thimble (metal loop) is often used to terminate your rope as sharp bends were once thought to produce excessive fiber heat under load. However, recent studies have shown that you are fine as long as the termination point the rope is wrapped around is of the same diameter of the rope or larger..
One caution to observe when using synthetic rope on a winch is that of overheating and degrading the fibers from the type of winch drum that uses internal braking action. One way to check for such damage is to unspool the rope and examine a portion of the first layer on the winch spool. The rope should still feel pliable and the strands should be able to move apart freely. Some rope suppliers will use a heat-protective sheath on the first drum layer of rope as a guard against heat degradation to the rope. Dyneema recommends that rope temperature stay below about 160 degrees F to prevent degradation. In essence, a colder rope is stronger, and a hotter rope is weaker.
Samson Rope is the maker of AmSteel Blue, a 12-strand braided rope made from Dyneema SK75 HMPE fiber. Here it's used to make a single-end loop for a rope thimble. It can also be spliced end-to-end. In essence, the end of one rope is pushed inside the hollow braid area of the mating rope, where it is choked tight under tension. Lock stitching with a needle and twine further secures the strands in place to prevent the rope(s) from creeping apart or separating while not under tension. Splices can generally retain 80 to 100 percent of the rope strength, while a knot connecting two pieces may offer only about half the strength of the rope. Most rope manufacturers offer recommended splicing instructions for their products.