Sew-up bicycle tires are very light-weight tires usually used on racing bicycles.

I would be tempted to say that sew-ups are high-tech, but they aren't particularly. My beloved Bianchi came with sew-ups in 1973, and the technology was by no means new then.

Ordinary bicycle tires are sort of semi-circular in cross-section, almost shaped like an Omega, in older models with tubes inside, and are held on the wheel by a metal rim on the wheel itself. Bicycle tire irons are strips of metal contrived to assist in prying the tire off the wheel. The dual structure, tire on the outside, tube on the inside, is quite durable and resistant to puncture. The downside is weight. All that rubber, two layers, plus the heavy rim, means weight.

And worse, rolling weight. Weight on the rim of a bicycle wheel is weight you must keep in motion as you bike: rolling weight. If there's a lot of it, the bike will feel sluggish, and you are working pretty hard to keep it going.

Sew-ups are, as the name implies, sewn up. The tires are one layer of rubber sewn together into a lateral circle with stiff thread. The sewn part is then covered with a glue-soaked strip of fibrous material, and the whole assembly is merely glued onto the light weight semi-circular wheel rim. Because the sewing and the gluing are quite strong, sew-ups can be inflated to about 100 pounds per square inch. So not only is the rolling weight very seriously diminished, the very high tire inflation means that a much smaller strip of rubber actually contacts the pavement, lowering friction as well.

Think, flying.

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