What do you call it? Do you say Rear Derailleur, Rear Mech, Rear Mechanism, ‘Mech’ or just ‘Gears’… they are all names to describe the mechanism typically controlled by a spring and cable that derails the chain and moves that chain out of one gear and into the next. I’m sure everyone has their favourite model and I am no exception; I’ve never tried to hide my love of Shimano, so my all time favourite rear derailleur has to be the Shimano Dura-Ace 7400. Even though it has a simple job to fulfill, the introduction and continued innovation of the rear derailleur has always been at the forefront of bicycle technology and the RD-7400 was in my opinion the start of the modern technology revolution.
I’ve recently had a perfect condition, and early RD-7400 6 speed derailleur delivered, I can only imagine based on its outstanding condition that it has only done a few miles. It is part of a set of components that I am slowly collecting ready to build SB6560, my 1984 531c Services des Courses road frame.
Finding one in this condition is extremely difficult – I don’t know what it is about Dura-Ace 7400 derailleurs but the vast majority are beat up and scuffed and although they all seem to function perfectly, the overall appearance is just as important for me as function.
I worked for many years selling bikes, working in a bike shop through the mountain bike boom of the 80s and early 90s, and a major selling point of many bike manufacturers was to give the rear derailleur an ‘upgrade’, so a bike at a certain price point and equipped with Deore LX would often have a Deore XT derailleur; that small upgrade to the derailleur gave the bike an edge against the others.
The reason for this upgrade is that most people viewing a bike will automatically view the rear derailleur, eyes are drawn to this component as it often carries the model name – it’s almost a signature of the quality of the bike you are looking at. So for me, although I might be able to hide the odd mark or scratch on some components elsewhere on the bike, the rear derailleur has to be as near perfect as I can get because I know it will always receive attention, the eyes will always focus on it.
I’ve been lucky to have some beautiful rear derailleurs on my bikes. My first build, SB4059 has a NOS PAT 80 Campagnolo Super Record derailleur; it came out of the original box, was fitted to the bike and is still unridden.
SB6827 is another bike that also has a beautiful Campagnolo Super Record rear derailleur, not only unridden, but also without a PAT marking and the later re-designed spring, making this one of the last of the Super Record derailleurs.
SB6398 has one of the most sought after groupsets amongst vintage bike collectors and includes the distinctive Campagnolo Super Record 50th Anniversary rear derailleur. It has approx 1000 miles on it and still looks amazing.
All of those Super Record derailleurs look great and work really well, but they weren’t exactly pushing the technological boundaries… amazing to look at but dare I say ‘normal’ in function. Even the replacement RECORD derailleur which looked superb, was still just a mechanism to derail the chain. At this point in time Campagnolo had not quite got past making stunning components, they hadn’t quite figured out that things needed to integrate and function better and not just be something to look at.
SB8868 however, has an amazing derailleur, one that was setting new standards in bike technology and innovation. The Dura-Ace 7402 Integrated 8 SIS rear derailleur not only looked amazing but functioned perfectly and gave that advantage of precise and exact gear changes every time. The individual parts of the Shimano system were designed to work together, shift levers, rear derailleur, chain, cassette and hub all had features that allowed the other components to work at their best.
But as brilliant as it was, the RD-7402 (8 speed) was still just an evolution of the original RD-7400 (6 speed) derailleur, very similar but very different. The 6 speed version was the original RD-7400 back in 1984 and launched Shimano’s Index System, catapulting Shimano into the limelight and giving the biggest wake up call to other manufacturers that they had to up their own game or risk losing ground. Shimano had been working on different technologies for a long time but it was the RD-7400 that gave the ‘fishing reel’ company dominance in the market. Have a read here for a look at my Dura-Ace 7400 timeline.
There were of course many other types from other manufacturers that I haven’t mentioned including popular models from Mavic, Suntour, Huret and Simplex – they all have their own fans, but you cannot hide the fact that the big two of Shimano and Campagnolo dominated this era.
My RD-7400 is actually a slightly updated version to the type originally launched – it differed by having a very subtle re-shape on the outer plate (item 10 below). The original RD-7400 had a slightly protruding edge at the bottom of the plate, mine has much more of a flat edge. This change was done to the RD-7400 before the introduction of the 7 speed RD-7401. This exploded view is dated January 1986.
The date code on this derailleur is ‘JK’.
According to an online Shimano dating system, the ‘JK’ code corresponds to November 1985.
This particular derailleur will soon be fastened to the Campagnolo 1010/B fork end on SB6560 as part of my own 6 speed Dura-Ace 7400 build.
The RD-7400 has been around for 34 years and even now its appearance and design still make it stand out amongst others. But the functionality this item brought to bikes and the role it played in kick starting the bicycle component revolution is why it is my favourite piece of kit.