Not your average barn find..

[mdvineng]

You can slide the jockey plates away from the sprockets! Longer plates were also available and the spring tension and foldback is adjustable too, all by undoing the pivot bolt.

 

[pigman]

You can slide the jockey plates away from the sprockets! Longer plates were also available and the spring tension and foldback is adjustable too, all by undoing the pivot bolt.

Cool, didn't know that, some design went into that mech then

 

[mdvineng]

I'm not sure what the max is, as it depends on the drop outs, there is some variation on dimensions. The Mavic front derailleur designated as two chain rings, quite happily changes a triple.
In the rear derailleur, the foldback spring retainer has a series of holes in it, to alter the tension and a movable tab to limit travel.

 

[ferrus]

You can slide the jockey plates away from the sprockets! Longer plates were also available and the spring tension and foldback is adjustable too, all by undoing the pivot bolt.

Looking at the 801 in the Mavic catalogue, that adjustability allows it to cope with a 30 or 32 tooth
Disraeli Gears calls the feature “cunning but only a partial success!” for some reason..

 

[Canyon_Si]

What are the brakes? They look similar to Modolo Kronos.

Keep the Mavic rear, it looks fab IMHO.

 

[Nob]

https://velobase.com/ViewComponent.aspx?ID=1caa5e1d-10a3-4fc4-b77a-a847f8073e21&Enum=117

 

[Canyon_Si]

Thank you @Nob

 

[Helmut Head]

I would love to keep the mavic derailleur but I'm not sure I would be able to make the necessary changes to make it work for me - I'm going to take the cowards way out and find a Shimano 600 Arabesque to go with the chainset and front derailleur. But don't worry the mavic will find its way onto something in the garage!