TS Isaac Cirrus

Tim Isaac built custom bicycle frames in Colorado under his own name from 1974-1979. He produced approximately 450 frames during this time, most with his signature fastback seat stays and hidden binder bolt. Tim also reportedly built eight frames for the 1980 USA Olympic team. While not ridden in the boycotted Olympics that year, the frames were ridden by American Olympic athletes in other competitions.
 
His frames were distributed by Texas Bicycle Supply of Houston. Tim would go on to make use his engineering background to manage production and design bikes for Acer-Mex, builder of Windsor bicycles in Mexico. He would join Trek in 1979 as a design engineer. Many people have seen his initals likely without knowing. The "TSI" in the cast bottom bracket shell of 1980s Trek steel bikes is him. Tim designed the socketed lugs and production process that enabled Trek to transform into a leading bicycle manufacturer. After Trek, Isaac founded Match Bicycles, a premium contract builder that produced the 60th Anniversary Schwinn Paramount, Rivendell bikes, as well as others.