Why Do Men's Bicycles Have a Crossbar?

Today's bicycles are oddly paradoxical machines. Materials technology has dramatically altered the composition of bicycle frames to the point where they have become virtually weightless and immensely strong. Yet that crossbar--technically called the top tube--persists, just as on the bicycles of a century or more ago.

  1. Origins

    • When the so called penny-farthings--those weird looking bikes with a huge front tire and the tiny rear one--were in vogue, it took a brave man to mount and ride one. An unseen pothole or a moment of inattentiveness could send the unwary rider careening over the handlebars and quickly off to the dentist. Something obviously had to change to make the burgeoning sport of cycling less dangerous.

    The Safety Bike

    • Enter the "safety bike." It still had two wheels but they were now identical, or nearly so, and considerably smaller in diameter than that of its forebear's front wheel. This new design put the rider much closer to the earth. Safer. Because it also sported a chain drive, the whole geometry of the bicycle had to be reinvented. Given the comparative lack of metallurgical prowess of the day, and the need to make the new frame configuration as strong as possible, the designers resorted to the strongest geometrical structure they could successfully utilize in building the bicycle frame.

    The Triangle

    • The triangle fit their needs perfectly. And, as if one were not enough, they built in another. The diamond frame they came up with consists of two triangles: a main triangle and a paired rear triangle. The rear triangle consists of the seat tube, and a pair of chain stays and seat stays. The main triangle consists of the head tube, down tube, the shared seat tube and our culprit--the top tube.

    Is it really necessary?

    • In those days it probably was really necessary. The triangle is an inherently strong structure, and particularly so when its legs are close to being equal in length. This meant that the top tube was integral to the strength and vital to the design. For whatever its shortcomings, and any of us who've ridden one have undoubtedly become painfully aware of those shortcomings, the design persists to this very day.

    It's About the Strength

    • It's truly amazing that in over a hundred years, the basic look of the bicycle has changed so little. Compare cars or planes or trains from that era to the current. Change did happen, though. As more and more women took up the sport of cycling, the need to modify that top tube became apparent. Long skirts were just too much of an impediment to swing over that bar. So, at the cost of a bit of strength, the "girls bike" was invented. Less robust? Yes, but then so were the riders! Vanity intact, we ride off into the future where aluminum, carbon fiber and super steels make any bicycle design possible, and strong as well. Yet that top tube persists. It may be modified somewhat by contemporary "compact" frames, but it's there nonetheless. A perfect example of "if it ain't broke, don't fix it."