After removing the retaining ring, remove the kickdown switch.
Using the tools, loosen the lock nut.

Tighten the adjusting bolt with a torque wrench (1) to 10 Nm, while holding the piston from turning. Then loosen the adjusting bolt by two turns and tighten it again to a torque of 5 Nm.

Loosen the bolt by 2.5 turns.
