Honda FourTrax Rancher TRX420FE1 2019 Owner's Manual page 184

Tires
Also, if you hit a pothole or other hard object while riding, stop as
soon as you safely can and carefully inspect the tires for damage.
Tread Wear
FRONT
(2)
REAR
(1) groove depth
(2) wear indicator
To check the condition of a tire tread, measure the groove depth (1)
in the center of the tire, or check the wear indicator (2).
For best performance, you should replace a tire before the tread
depth at the center reaches the following limits:
front
rear
174 Servicing Your Honda
NEW
3/16 in
(4 mm)
Replace
3/16 in
(4 mm)
Replace
NEW
3/16 in (4 mm)
3/16 in (4 mm)
(1)
(3) wear indicator
location mark
(3)