Should climbers worry about microfractures? Many climbers had been taught that if a carabiner falls and hits the ground from more than a few feet it should be retire because microfractures, cracks smaller than they eye can see, may have developed. Is that overly cautious? To find out we bought 6 Mammut Crag Wire Gates and 6 Mammut Wall Micro Lockers, abused 3 of each as a test group, left 3 alone as a control group, and broke all of them on our slacksnap machine. Did any the abused carabiners lose strength?
Our test carabiners endured at least 100 times hard throw directly against hard granite. They were so chewed up that the gate tension on the wire gates had softened noticeably. We then hooked them up to the slacksnap, broke them all, and used a LineScale2 dynamometer to measure the results.
A couple of the abused carabiners broke slightly below their rated minimum breaking strength (MBS). This may mean the abuse weakened them, but it may also be from variation normal variations in the aluminum carabiners. The lowest breaking score was still over 4,700 pounds, which is far more than a climber will ever generate in a normal climbing scenario. In short, all of the carabiners were still super good enough, at least when it comes to strength.
So are microfractures a myth? We will let you decide. We abused these carabiners well beyond what we consider normal drops, but remember this is edutainment and our results should only be part of your personal verdict on this issue.
Gear retirement is a complex decision and a variety of factors are important when deciding if a carabiner is still good or not. Carabiners do sometimes develop cracks and other defects that can compromise their strength and efficacy. Take care of your gear, inspect it regularly, and if in doubt consider retiring anything suspect.
Thank you Bobby Hutton for filming and helping break test.
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