Is there any reason why Formula brakes should use Formula rotors, apart from the warranty being void. They cost so much! Any recommendations on what rotors to use?

I’ve used Shimano and generic rotors with no problems.

Superstar ones are pretty good IME.

I’ve mixed and matched shimano and formula before with no issues.

You can sometimes get their floating rotor ones pretty cheaply from the ‘special offers’ section of the Formula Store.

EDIT: Just looked, and you can, but they’re all off on their summer holidays until September. Wish I lived in Italy…

The Formula warranty/disclaimer blurb is a masterclass in management of liability for mechanical failure and accidents. (fortunately the uk distributor/warranty is pretty fine in my experience of 2 failed levers on brand new and not-so-new brakes) I have used centerlok shimano rotors on my old k18’s a few times and they were fine. FWIW formula rotors are really nice and although the law of diminishing returns for money spent very much applies, they are lightish and stop and cool pretty well.

I’ve used Shimano center-lock and also some cheap randoms (Clarks?) with my Forumla RXs without any issues.