Shimano GRX RX 815 Series Dealer's Manual page 169

MAINTENANCE
Replacing the brake hose
NOTICE
• Do not let the brake hose become twisted when installing it.
Make sure that the calipers and levers are in the positions shown in the figures.
Left hand lever
Right hand lever
4.
Tighten the connecting bolt while pushing on the brake hose.
Connecting bolt
5 - 7 N·m
169