Honda NRX1800 2004 Owner's Manual page 143

Tires
You should replace the tires with tires of
the same size, load range, and speed rating
as the originals.
Installing improper tires on your
motorcycle can affect handling
and stability. This can cause a
crash in which you can be
seriously hurt or killed.
Always use the size and type of
tires recommended in this owner's
manual.
134
Servicing Your Honda
The recommended tires for your
motorcycle are:
150/60R18M/C 67V
front
DUNLOP D251F
180/55R17M/C 73V
rear
DUNLOP D251
Whenever you replace a tire, remember:
Have the wheel balanced after the tire is
installed.
The motorcycle is equipped with
adhesive wheel balance weights.
Use genuine Honda parts for
replacement.
Have the tire replaced by your Honda
dealer if possible.