In 1984 MAVIC updated its MAVIC 800 derailleur, and spawned two new models the MAVIC 801 and the MAVIC 851. The two models were virtually identical, except in one crucial regard - the 801 was largely silver, but the 851 had dark, hard-anodised, parallelogram plates and a coach line on its pulley cage. This gave the 851 a brooding, rebellious look that matched perfectly with the, then ultra-desirable, also hard-anodised, macho MAVIC SSC rims. A star was born.
It would be churlish to suggest that a touch of hard anodising and the odd coach line might have meant that the production cost of the 851 was perhaps all of one French Franc higher than that of the 801. But that did not stop the 851 from living up to its 'ultimate' billing by costing the bedazzled consumer substantially more than the plain vanilla 801. Style is almost always more valuable than content. If the Three Kings turned up in Bethlehem today they would be bearing gold, frankincense and a gift voucher for the services of a personal stylist.
I know of four variants of each of these derailleurs:
This may be a slightly abridged history - I have also seen an 801 where the large allen bolt at the p-pivot has a female, rather than a male, thread. These are 'artisan' products, and any batch may vary in any way at any time.
Afficionados love these derailleurs. Part of this may be because they were favoured by legendary cyclists - Sean Kelly was a fan of the MAVIC 851 and Greg Lemond won the 1989 Tour using one. Since 1946, the MAVIC 851 is the only Tour winning derailleur that was not from one of the major, million-selling, brands of the time: Huret, Simplex, Shimano, SRAM or Campagnolo.
But part of this love is also because of the overall industrial design of these beauties. Here I have to differ. The adjustable cage is fiddly, arguably useless - as nearly all these derailleurs ran over close ratio frewheels, and the strange flanged clamp nut frequently cracked. The black pulley cage plates, the painted logos and, on the 851, the hard anodised paralelogram plates all became scratched. And finally the pulley cage plates had lost their pure geometrical form. Playing the role of curmudgeonly baby-boomer, I much prefer the MAVIC 800.
Finally I should note that MAVIC sometimes calls the 801 the 'MAVIC 801 Pro' and the 851 is sometimes called the 'MAVIC 851 SSC'. 'SSC' stands for 'Special Service Course' and references MAVIC's status as provider of the neutral service vehicles at major races. It implies that components bearing this name are for the very toughest professionals riding the very toughest races - think Sean Kelly riding Paris-Roubaix. These extravagant names tended to appear in the derailleurs' later years and seem to be especially prevalent in materials for the US market. In earlier years labels like 'SSC' seemed to be reserved for rims and groupsets.
I always like to include one or two 'hard working' examples' of the most famously beautiful derailleurs. I see them as one-time matinée stars who have hit the skids, with lank hair and wrinkled grey skin that tells us more about the geography of real life than the airbrushed headshots that date from their prime. I think that this, very battered, MAVIC 851 dates from around 1985, mainly because it has both a painted logo and the old-style rotation stop for the pulley cage. Some of its key features may be:
Note that these earlier MAVIC 851s have a claimed maximum sprocket size of 32 teeth - later versions were supposed to handle only 30 teeth. Personally I would have worried about anything over 28 teeth for any of them - but that's me.
Finally I should also comment that, on this example, the tension pulley bolt is not original.