Asking as I am in the market for some new brakes and I already have the rotors 180/160

Ta rich

I doubt a missing 1.5mm of rotors will matter much.

Just use Shimano adaptors.

Buy the brakes with rotors, ebay what you don't need?

Presumably they'r all the same (appart form avid who have extra spacers), as you can buy forks with different sized mounts, it'd be a pita buying forks for 7" rotors when you need 180mm (for example). I imagine the difference between a nominal 6" calliper/rotor combo (hayes) and a 160mm rotor/calliper (shimano) is in the calliper.

If they're post mount type adaptors then just file off 1.5mm of material from the top of the adaptor. If you mark it before starting the filing then you should be able to get a clean finish.

Just the reverse of the use of washers between adaptor and caliper to increase from 180mm to 183mm.

Shimano adaptors are £5 each and are nice soft aluminium for filing.

Looking @ prices on wiggle i,m better off buying the full set and selling the rotors!

Ta very muchly