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Sure, your draws came in neon pink and they match your harness, but how were they tested and what were they actually certified to be safe for? Most climbers give little to no thought about the kind of carabiners they buy or the ones pre-hung, shiny and danglin’ at the local gym.
There’s a lot that goes into these seemingly simple devices. Everything from the shape, to the nose type and angle, to the gate affect strength and utility. As long as you’re buying from reputable sources, your climbing biner is plenty strong, but the devil is in the details.
The first thing to look for on your carabiner are the acronyms CE or UIAA, both of which will tell you that the carabiner is safe for climbing. To the uninterested, read no further—those neon colored draws your aunt got you for Christmas will do just fine.
But to the more discerning consumer, here’s everything else you need to know about picking the best carabiner out of a lineup.
Following the CE or UIAA acronyms, all carabiners will have a set of three numbers indicating the kilonewtons of force the carabiner is rated to handle. The first number (23 kN in the above example), next to the arrow that would imaginarily run straight across the letters and numbers, indicates the kilonewtons the carabiner can take if the force is parallel to the spine, or along the “major axis.” This is the intended direction of force for carabiners and accordingly will have the strongest rating.
The next number indicates the force the carabiner can withstand perpendicular to the major axis, or along the “minor axis,” also referred to as cross-loading. This number (8 kN in the above carabiner) will often be one third of the first number because carabiners are not meant to be turned horizontally when the climber falls. They are still rated, however, to withstand climbers’ biggest whips.
The last number (8 kN again) is the force the carabiner can withstand while the gate is pushed open, but still hanging from the hanger in its upright position. This number will resemble the previous number or may even be slightly less. While atypical, climbers do occasionally fall when a gate is slightly open, sometimes due to a protruding rock feature.
In case it’s been years since your last physics class, here’s a quick lesson: A kilonewton is a measurement of force, which is the product of mass and acceleration. Think about how a heavy climber taking a big fall generates tons of force.
Just a reminder, force is not the same as weight. If you’re hanging motionless from a draw, you have zero acceleration and therefore zero force. Many people want to know how much weight a carabiner can support, but manufactures typically won’t give you that info because it’s not applicable to climbers, who put massive amounts of force on a carabiner when they fall. Industrial carabiners, made of steel rather than aluminum, are capable of sustained heavier loads, but they’re also cumbersome and overkill for climbers.
Carabiner shape is an important factor in determining strength and safety. There are two main shapes used for draws that you should be aware of: D and asymmetric D. The D shape is the strongest, however the asymmetric D is the more common choice because the asymmetry allows for a large gate opening and easier handling. For both shapes, the UIAA denotes the same minimum strength standards for each axis: 20 kN for major axis, 7kn for minor axis and 7kn for open gate.
Gate and Nose Type:
The next factor climbers face in choosing the right carabiner is gate type. Gates are either wire or solid, with solid gates typically being slightly heavier. With solid gates, climbers must be wary of gate flutter, which occurs when vibrations from the rope causes the gate to open and close rapidly. Gate flutter is rare, but it happens, putting the climber at potentially serious risk. Alternatively, wire gates are lighter than solid gates and therefore will not flutter. They’re also stronger than their less bendy counterparts.
The caveat with wire gates is that they’re often fitted with a non-keylock (hooked) nose, which significantly increases the chance of the draw snagging on gear or bolts. Because force is not intended to be applied to a carabiner that is hanging from the nose, the nose is the weakest part of a carabiner. For this reason climbers should look for keylock (hookless or solid) noses and take care to adjust shifted draws while climbing.
One more nose type thing to consider: Nose Shrouding. Think of nose shrouding as a hood covering the hook part of the nose, making snagging less likely on non-keylock noses. Even just a little bit of shrouding can go a long way in preventing accidents.
Both solid and wire gates come in straight or bent shapes. Straight is safer because it’s less likely to be pushed open if wedged against something. Many climbers, however, prefer bent because it makes clipping easier.
When it comes to safety, nose angle is almost as important as nose type. Keylock or not, carabiners can have a smooth flat curve leading to the back spine or be sharply angled. The more dramatic the nose angle the higher the snag potential, so smoother is better.
In summary, if you want the safest, strongest carabiner on the market, look for UIAA or CE certified carabiners that are D shape with a straight wire gate, keylock nose (or non-keylock with shrouding), and have a smooth, flat nose-angle. The most important things to look for, aside from the certification, are nose type and angle.
Don’t forget to regularly inspect your gear after putting it to use. Retire the carabiner if sharp edges are forming or if the gate feels weak.
Again, climbing carabiners are tested for force, not weight, but this is still cool: