This weirdo downhill derailleur, operated by compressed air, was the famous product of Shimano’s Skunk Development Team. This was modelled on the legendary Lockheed Skunk Works, which is popularly assumed to have acquired its name as a result of spectacular achievements in the field of personal hygiene by the engineering geniuses who worked there (this is not the ‘real’ story).

Shimano’s rationale in developing Airlines was explained to me as being that compressed air lines flex with long travel suspension (which makes using cables difficult) and are not affected by water (unlike electrics), and so control by compressed air was particularly suitable for downhill bikes.

However, Shimano’s own booklet, ignores these points and, instead, stresses the speed of the gear change and the fact that the rider only has to ‘dab’ the lever to initiate a change, both of which are apparently important in the heat of a downhill race.

I am struck by the way the ‘machined from solid’ look and the external spring echo the Sanko Procyon. Both designs were, in their different times, at the very furthest edge of existing technology.

An interesting irrelevance.

• Derailleur brands: Shimano
• Categories: Shimano - weirdness
• Country: Japan
• Date of introduction: 2000
• Date of this example: 2000? (no two letter date code)
• Model no.: AR01
• Weight: 329g
• Maximum cog: 26 teeth
• Total capacity: 15 teeth
• Pulley centre to centre: 49mm
• Index compatibility: 7 speed
• Chain width: 3/32”
• Logic: top normal
• B pivot: sprung
• P pivot: sprung
• Materials: aluminium, steel inner parallelogram plated