Flat mount brakes rotor size

Flat mount is new to me so I’m after confirmation of parts compatibility/ need before orders go in for a bike build.

Titus goldrush frame

Shimano grx rx400 rear caliper

Does a 160mm rotor fit the frame and do I need to also order a rear fm to fm +20 adapter in order for the caliper to fit the 160mm rotor?

Thanks

Depends on whether it’s a native 140 or 160 mount.

if the former, it needs the adaptor, if the latter, it bolts directly on.

Ha! Makes sense.

This one

https://www.cyclesolutions.co.uk/components/brakes/shimano-grx-rx400-hydraulic-disc-brake-caliper–rear__52698

I can’t see of it says 140 or 160…I’m guessing 140 with no adapter.

The caliper is irrelevant, it’s the frame that determines the native rotor size.

Is it, great,  I shall check with px then.

Pretty sure the gold rush is 160 without using a rear adapter

Have you got the frame yet? Hope website has some technical drawings that give you the measurements to confirm which type of mount the frame is