With these models Schwinn achieved a nice balance of frame rigidity and smooth handling.

Although they were fabricated in the same shop as the Paramounts, from there Schwinn's fillet-brazed frames took a different production path.

Yet unbeknownst to most of us Schwinn was actually using three types of frame tubing and construction, which meant that there were three classes of Schwinn ten-speed bicycles : The fillet-brazed Cr Mo frame construction of Schwinn's second class of lightweight bicycles - the Superior, Sports Tourer and Super Sport - was unique.

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The extra thickness of the fillet also provides strength, and its smooth contour distributes stresses evenly.

(For additional strength Schwinn also brazed steel sleeves into the interior of its frame tubes at the joints.) Fillet-brazed bicycle frames are strong and have a neat and clean appearance, but they are uncommon because of the additional craftsmanship required.

Frame tubes were mitered in a jig by machine, and then the remaining fabrication work (brazing, filleting, braze-ons, and finishing) was done by hand.

The seat and down tubes, as well as the top tube on the largest frame sizes, are slightly oversize at 29.5 mm in diameter.

Fillet-brazing is an alternative method of constructing high-quality lightweight bicycle frames without the use of lugs.

Brazing is a joining process employing a filler metal, like brass, that melts below the melting temperature of the parent metal workpiece.In time bicycles became less expensive, but by the end of World War I automobiles had taken their place as the popular form of transportation.Bicycles began to serve more as vehicles for children, which led to the development of heavier and sturdier models. became primarily a producer of heavy-duty juvenile bicycles.(The author does not know why lugs were not used for these frames.Perhaps in those days manufacturing lugs was more expensive than hand brazing.) Schwinn's practice of offering this style of bicycle as its second-highest models continued until 1978.Schwinn's fillets at the head tube are usually well finished, but other joints are sometimes sloppy or not fully smoothened.