Ducati Multistrada 620 2005 Manuel D'utilisation Et Entretien page 167

Minimum tread depth
Measure tread depth (S, fig. 70) at the point where tread
is most worn down.
It should not be less than 2 mm and anyway not below the
S
legal limit.
Important
E
Visually inspect the tyres at regular intervals so as to
detect cracks and cuts, especially on the side walls, and
bulges or large spots that are indicative of internal damage.
Replace them if badly damaged.
Remove any stones or other foreign bodies caught in the
tread.
fig. 70
74