Can any one point me in the right direction of a 180mm adapter for said caliper. I have got 180mm rotors and the caliper is IS mount but searching round the tinternet I can only find adapters that add another 20mm which is ok but I could do without forking out another £40 for a bigger floating rotor.
IS calliper and post fork, you'll have to add 20mm.
You should be fine with 180mm rotors. This is what I had to use when I had a Magura Marta IS caliper on on a PM Bomber fork. You would not be able to put a 160mm disc on that setup but 180mm with that adapter will work fine.
you want one of [url= https://clee-cycles.co.uk/cc/catalog/product_info.php/cPath/21_123/products_id/989?osCsid=8nmp2rm7o3n5iv33teveoskte2 ]these[/url] adaptors. I used it to fit a Hope XC 180mm IS mount brake to a set of post mount Rock Shox. No need to go up in disc size or anything.
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Looks OK and works just fine. PS it looks pink on the website but it's red.