Honda CB500XA Owner's Manual page 74

Maintenance Fundamentals
# Inspecting Tread Depth
Inspect the tread wear indicators. If they
become visible, replace the tyres immediately.
For safe riding, you should replace the tyres
when the minimum tread depth is reached.
or TWI
Wear indicator
location mark
70
WARNING
3
Riding on tyres that are excessively
worn or improperly inflated can cause a
crash in which you can be seriously hurt
or killed.
Follow all instructions in this owner's
manual regarding tyre inflation and
maintenance.