The Shimano Ultegra (6770 SS) has a topsy-turvy history:

• It was released, with great fanfare, as Shimano's first 'affordable' Di2 racing derailleur. Everybody that I knew in the industry was convinced it was a game-changer that was assured of runaway success.
• Then it somehow fell flat. Despite being 'affordable' it was extremely expensive and was selling into an economy that was still struggling its way out of the 'Credt Crunch'. And the derailleur itself was heavy, clunky and somehow a touch ungainly, with its fat-ass look. Bikes fitted with the 6770 were proving sticky to sell.
• Then, as the launch of the 11-speed Shimano Ultegra (6870 SS) loomed into view, everyone panicked. Suddenly the market was awash with special offers, and even special models, in a desperate attempt to shift the 10-speed 6770 groupsets before they were obselete. This proved to be exactly what the market wanted, customers did want Di2, but just could not afford it at the original prices. The new price was perfect, and surprisingly few people cared about the one sprocket difference.
• But the 6770, as a first generation product, did not prove quite as reliable as Shimano's regular fare. And buyers of the discounted bikes did not prove quite as lovingly careful as buyers paying the eye-wateringly expensive regular price. And so demand for replacement Ultegra 6770's started to grow. And there was a problem - everyone had cleared their stock. Shimano had also not quite thought things through. There were no acceptable substitutes for the 6770, certainly the Shimano Ultegra (6870) was utterly incompatible. You needed a 6770 derailleur or you had to throw away your whole 6770 Di2 set up.
• And so it came to pass that the Shimano 6770 derailleur became one of the most sought after derailleurs in the world, with nice examples fetching astronomical prices on ebay.
• Outraged consumers bombarded Shimano with vitriolic criticism, but initially Shimano had no answer. They had moved on from the electric motors in the 6770 and could not source any more. Finally they devised a new 10 speed derailleur, the Shimano Ultegra (6770-A SS), by fitting the mechanical elements of the 11-speed Shimano Ultegra (6870) with new electronics that turned it into a 10-speed.

The whole sorry saga does illustrate an important point. In the world of mechanical groupsets it has long been appreciated that part of the product designer's art lies in the striking of a delicate balance between two factors. On the one hand, groupsets genuinely work best if all the elements are tightly designed for each other with extremely specific chains, sprockets, levers, cables and derailleurs. But on the other hand, utterly exclusive groupsets cause no end of problems as, if even one component becomes unavailable, the whole groupset becomes unusable. And so the designers accept a few compromises and you can usually use a Shimano 105 level chain with a Shimano Ultegra groupset etc. etc..

The arrival of electronics makes this problem more acute. Electronic systems are evolving very quickly, so maintaining any kind of backwards-compatibility risks compromising the performance of new systems. But the highly integrated nature of these systems means that not maintaining backwards-compatibility risks alienating some of your highest value customers. My guess is that Shimano is betting that most early electronic gear consumers will just dispose of their bikes after a few years and move onto a new one - reducing the value of backwards-compatibility. I would bet that, in Britain at least, they may be reading this wrong. In my experience, even the most driven equipment junkies like to sell their 'old' bikes for a healthy price - and this is not going to happen if the bike is essentially un-repairable. It's going to be an interesting few years.

• Derailleur brands: Shimano
• Categories: Shimano - the Ultegra story
• Themes: Electric Avenue
• Country: Japan
• Date of introduction: 2011 (for the 2012 model year)
• Date of this example: September 2012 (two letter date code 'KI' on foil sticker on b-knuckle)
• Model no.: 6770 SS
• Weight: 272g
• Maximum cog: 28 teeth (source: Shimano)
• Total capacity: 33 teeth (source: Shimano)
• Pulley centre to centre: 56mm
• Index compatibility: 10 speed
• Chain width: 3/32”
• Logic: top normal/electronic
• B pivot: sprung
• P pivot: sprung
• Materials: largely aluminium with steel inner parallelogram linkage and a carbon p-knuckle