Setup: Front, RS Lyrik, Formula 203mm rotor, Formula 203mm post/post adaptor, Shimano SLX caliper.
Rear, Formula 180mm rotor, Formula 180mm IS/post adaptor, Shimano SLX caliper.

On the rear, the pads are perfectly centred over the braking surface, with their contact ending at the base of the rotor spokes. On the front, however, there’s about a 2mm area above the spokes that the pads aren’t contacting.

Reckon a Shimano 203mm post/post adaptor will sort it, or should I bite the bullet and get Shimano rotors as well?

Shimano floating rotors are brilliant and stay true

I’m sure they do, but that’s not what what I was asking! When I say centred over the braking surface I mean radially, not laterally.

Formula rotors are 200mm not 203

That’s your problem – there are ways to bodge a 203mm mount to make it fit; or you buy the avid mounting kits (too much hassle for me)

Just buy a new rotor tho – it’s easier

Probably what tmb467 said, I just had a frustrating time trying to get a rear brake to line up properly. Solution was in the end to buy matching shimano adapter and rotors.

The bottom of the rotor track isn’t such an issue, it’s only an issue if either the rotor touched the caliper or the rotor doesn’t sweep the whole pad (leaving a lip on the pad at the top).

I’ve had to shim both shimano & super star adaptors using hope washers, probably more down to the frame than the adaptor though

if you fit shimano adaptors with shimano discs and shimano brakes then they will match in all dimensions unless the frame tolerance is not spot on.

Formula rotors are 200mm not 203

Not the one I have fitted – definitely a 203! Was supplied direct from Formula, along with the 203mm Formula adaptor.

Will have to pop the pads out to check they’re not getting lipped at the top edge. If they are I’ll just mill down the adaptor; if not, guess I’ll leave it and buy Shimano rotors and adaptors when these wear out.

IS mount faces, adaptor faces, and the calipers themselves are often well out of tolerance.

If you look at the pro’s bikes, they have often faced the adaptors and calipers by hand.