Have a look at this, [url= http://www.chainreactioncycles.com/Models.aspx?ModelID=62056 ]http://www.chainreactioncycles.com/Models.aspx?ModelID=62056[/url] when purchasing there is a list of various options, post mount, IS, rotor sizes, left/right hand levers etc etc and multiple combinations of. I can't for the life of me think what the 5inch, 6inch, 7inch, 8inch options are next to the rotor sizes. They presumably relate to the rotor size in some way. anybody?
Rotor size is exactly correct; it's just the metric sizes (140mm diameter etc.) expressed in inches. They are only nominally correct though, 5" is not exactly 140mm, or vice versa (in fact 140 is more like 5.5"). Which I guess is what is causing the confusion. Don't get hung up on the conversion between units, they're just nominal sizes anyway. Think of them as two names for the same thing.
But if you look at the listings there appears to be a 5" and 6" post mount version for each rotor size (e.g. 160mm 5" post mount and 160mm 6" post mount) and 5", 6" and 7" post mount versions of the 180mm rotor. The imperial size appears to be connected to the post mount, rather than the rotor size.
Oops sorry, just been back to actually read it! I thought all post mounts are 6" (160mm), i.e. with caliper bolted straight to the mountings it would suit a 160mm rotor. As you rightly say, the listing suggests there are different post mount sizes? Didn't know that!
Maybe it's because if the move to post mounts on the frame (ie the rear brake) that is starting to emerge? I know the listing has right lever with the options, but these are from Germany, where they would have the right lever for the rear brake?
I think it's a listing error. What on earth is a 5 or 6 inch postmount?
They've mucked up the descriptions I think - Magura only used metric sizing.
I thought it might be a mistake, but it's the same on wiggle
[url= http://www.wiggle.co.uk/magura-marta-sl-magnesium-disc-brake-with-storm-sl-rotor/ ]http://www.wiggle.co.uk/magura-marta-sl-magnesium-disc-brake-with-storm-sl-rotor/[/url]
Or the different rotor sizes could come with brackets to suit?
Could it have anything to do with the fact that Magura Wotan forks only accept 203mm rotors and the caliper is post mounted there.?
Possibly it's their uk translator. The Wotan manual is most amusing in places.
Some magura forks have brake mounts to fit rotors bigger than 6" without adaptors - This is what they're for.