Ducati Diavel Carbon ABS Owner's Manual page 167

Minimum tread depth
E
Measure tread depth (S, fig. 159) at the point where tread is
most worn down.
It should not be less than 2 mm, and in any case not less than
the legal limit.
Important
Visually inspect the tyres at regular intervals for cracks
and cuts, especially on the side walls, and bulges or large
stains that indicate internal damage. Replace them if badly
damaged.
Remove any stones or other foreign bodies stuck in the
tread.
166
S
fig. 159