Shimano Dura-Ace AX Rear Derailleur Circa: 1980 On display in Bikeman's Museum is a Shimano Dura-Ace AX rear derailleur. This derailleur was introduced in 1980 as Shimano's first attempt at an aerodynamic parts kit. The derailleur's design was as narrow a profile as possible, even using extra material over the upper pulley to direct wind away from the rest of the derailleur.
The Shimano website give this description of the entire group: "The Dura-Ace AX components are introduced at the International Cycle Show in Cologne, Germany. The group is based on an innovative new aerodynamic design theme. Through the use of the bicycle industry's first wind tunnel, Shimano engineers developed a component series with 20% less drag than contemporary designs." Shimano's quest to produce the best performance products available is evident.
The other most obvious feature, other than the slight profile, is the interesting cable holder on the back of the derailleur. This was designed to take the bare cable, without housing, and feed it to the pinch bolt. Many bikes of this era had a cable guide mounted on the seattube just above the bottom bracket shell. The bare cable would run from the downtube shifter under the guide and straight to the rear derailleur. No housing needed. A creative solution to cable drag!