Unlace Me — A shoelace replacement and lacing | unlace-me.com
Walking hits the knot with 6-8 g of acceleration; a weak knot slips, whips open, and is fully untied within one or two strides.
UC Berkeley measurements put the acceleration at the knot during walking at 6-8 g, and the lab rig reproduced the same failure at about 7 g. Each stride both strikes the knot and swings the loops and free ends.
The failure has a signature speed. Once slipping starts, the knot finishes untying in 1-2 strides — roughly 1-2 seconds — because the swinging free ends whip the loosened knot open. Observed walking failures landed within about 50 ft.
Knot structure decides survival. With 3 g of weight hanging on the free ends, the weak granny knot failed in 100% of trials; the strong square knot failed in 53% (8 of 15). Direction matters as well: side impacts failed 40% of strong knots at 2 g, while rear impacts failed none at that level.
On narrow screens, swipe or scroll the plate sideways.
The trials ran under fixed conditions — 2 mm unwaxed round dress laces, loops and free ends set to 8.26 cm each, a 15-minute timeout, filmed at 900 fps — so the 100% vs 53% gap compares knot geometry, not lace quality.
The fix takes two steps and no new laces. First, check the bow: a granny knot twists to sit along the shoe, while a square knot sits straight across it. Second, retie with the second crossing reversed — right over left, then left over right — and the bow holds under the same 6-8 g that opened the granny.
If the bow holds but the lace still feels wrong, the problem is length rather than knot: the eyelet chart on the length page gives the right size, and the 5-step re-lacing procedure shows how to thread it.
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