RITCHEY OUTBACK BRAKE COMPATIBILITY
Flat-mount brakes front and rear: 140mm (160mm max - adaptors available separately)
Frame flat-mount bracket height: 10mm
Shimano GRX
GRX 820
BR-RX820 (x2) (weight - rear: 135g; front: 146g) [~$84 rear; $90 front]
Recommended disc brake rotors (x2): RT-CL800 (140mm) (weight: 97g)
GRX brake calipers: 11 and 12 speed
It’s a similar story with the hydraulic disc brake calipers, which appear to be the same BR-RX820 model that Shimano debuted with the GRX Limited groupset (BR-RX820-LE), just in a dark anodized finish instead of the bright silver polish. It’s functionally equivalent to earlier models in terms of braking performance, but is supposedly easier to bleed and with a bit more pad clearance to boot.
For GRX 610 (GRX 400)
BR-RX400 (x2) (weight - rear 109g; front: ) [~$55 each]
Recommended disc brake rotors (x2): SM-RT64 (140mm) (weight: ?g)
Bike Sauce
Brakes: Growtac Equal Flat mount https://velo-orange.com/products/grow...
Rotor size
rotors 140mm versus 160mm gravel