Shimano Dura-Ace SIS (7402 1st style) 31232

Today, we are all aware that the current Shimano Dura-Ace derailleur probably holds the meaning-lite title of 'best derailleur in the world'. Of course every pub in the land will house a self-appointed expert who holds a provocative (and interesting) opinion that they prefer some other, not quite so obvious, model from some other, not quite so obvious, brand - but that is what pub arguments are for.

In 1983, however, things were not quite so straight forward. The 1977 Shimano Dura-Ace (7100) was pleasant, but slightly underwhelming. The 1978 Shimano Dura-Ace EX (7200) was more technically interesting, but by 1983 was kind-of average and very long in the tooth. The 1980 Shimano Dura-Ace AX (7300) was so overly 'interesting' that most consumers of top-end equipment gave it a body-swerve. The Dura-Ace name was struggling and 'best in the world' seemed some distance away.

And then the Shimano Dura-Ace SIS (7400) groupset hit the scene. It had four stand-out attributes, one obvious, and the other three more obscure, but, perhaps, equally important:

Firstly and famously, it introduced the world to SIS, Shimano Index System. The first-ever approach to indexed gearing that worked accurately, reliably, smoothly, subtly and pleasurably.

But also:

SunTour's patent on the slant parallelogram had expired, and so Shimano was, finally, able to deploy the 'best fundamental design in the world'.
Dura-Ace (7400) was manufactured, and finished, to a magnificently high standard. It could seriously claim to be the 'best made derailleur in the world' - a claim that I would happily endorse.
It was styled in a new Shimano design language, which combined a certain minimalism with subtle anodised colours and simple elegant forms. It was a derailleur for adults and, more than that, adults with taste. At the time I would call it 'the best looking derailler in the world'.

Starting in 1984, Shimano rapidly came to dominate the world of high-end components. SIS was, of course the fundamental driver of this - but I suspect that SIS alone wouldn't have worked. If the Sachs-Huret Rival (41.1D) had had reliable indexing it would not have had nearly the same impact - because it was slightly crudely manufactured and, whisper it quietly, plain ugly.

The final oddity was that, in my experience, Shimano Dura-Ace (7400) hardly sold at all. Road bike sales were pretty low in 1984 - and things only got worse and worse over the next decade as the revolutionary new mountain bikes came to completely dominate the market. I found that selling bikes equipped with the eye-wateringly expensive Shimano Dura-Ace SIS (7400) was virtually impossible in the UK. For that market, at that time, they were a totally wrong sort of bike at a totally wrong sort of price point. But as so often in the early history of Shimano Dura-Ace, that misses the point. In the UK, at least, Dura-Ace (7100) and Dura-Ace EX (7200) only sold OK, but established Shimano as a company that was ambitious enough to get involved with the pro-peleton. Dura-Ace AX (7300) sold pretty poorly, but established Shimano as a technology leader. And Dura-Ace SIS (7400), however well or badly it sold, established Shimano as 'the best in the world'.

I suspect that Shimano was more than delighted to rake in the shed-load of mid-range sales that its new reputation generated.

I am aware of 5 different variants of the 7400 series rear deraillleurs. I think that their distinguishing features might be as follows:

The first version (1984) was a 6-speed with model number 7400. At the b-pivot there was no adjustment screw and no external plastic seal. The cable adjuster did NOT have a spring loaded 'click' mechanism. The cable clamp nut took a 6mm allen key. The pulley cage was 47mm centre-to-centre, the outer pulley cage had a pronounced hook at the guide pulley and the pulleys had bronze bearings.
The second version (1985) was also a 6-speed with model number 7400. However it now had an adjustment screw and external seal at the b-pivot. It also had a redesigned 48mm pulley cage plate and ceramic bearings in its 6-speed pulleys.
The third version (1986) was a 7-speed with model number 7401. It was extremely similar to the second version, above, but had 7 speed pulleys. The outer pulley cage plate was labelled '6S-7S SIS'.
The fourth version (1988) was an 8-speed with model number 7402. This was an extensive redesign with changes to nearly every part. The b-pivot had an obtrusive plastic shield, the p-pivot was now concealed, the cable adjuster had a spring loaded click, the cable clamp nut took a 5mm Allen key and there was a dial to change the parallelogram spring tension. The pulleys were 8 speed units with rubber seals. The outer pulley cage plate was labelled 'Integrated 8 SIS' and was round at the tension pulley. The inner pulley cage plate has no 'tab' at the tension pulley.
The fifth version (1988) was also an 8-speed and also sported the model number 7402. This was very similar to the fourth version. However, the outer pulley cage plate has a pronounce bulge at the tension pulley. The inner pulley cage plate now has a 'tab' at the tension pulley.

This is an extremely high mileage example of the fourth version described above. The pulley wheels are extremely worn, but the rest of the derailleur is well used but in surprisingly attractive condition. Some key features are:

It is clearly labelled with model number 7402.
The b-pivot has an adjustment screw but is missing its prominent external plastic guard.
The p-pivot is concealed.
The inner parallelogram plate has a built-in parallelogram spring tension adjuster.
The cable adjuster has a spring loaded 'click' mechanism.
The cable clamp nut takes a 5mm allen key.
The pulley cage is 48mm centre-to-centre. The outer pulley cage is labelled 'Integrated 8 SIS' and is smoothly curved at the tension pulley, with no bulge. The inner pulley cage plate has no 'tab' at the tension pulley.
It has 8-speed pulleys with ceramic bearings and flexible rubber seals.