Honda Pioneer SXS500M 2018 Owner's Manual page 175

Also, if you hit a hard object or obstacle while driving, stop as soon
as you safely can and carefully inspect the tires for damage.
Tread Wear
FRONT
wear indicator
REAR
To check the condition of a tire tread, measure the groove depth in
the center of the tire, or check the wear indicator.
For best performance, you should replace a tire before the tread
depth at the center reaches the following limits:
front
rear
groove depth
3/16 in (4 mm)
3/16 in (4 mm)
3/16 in (4 mm)
Servicing Your Honda
Tires
wear indicator
location mark
165