Honda VTX1800R Owner's Manual page 129

Tires
The recommended tires for your
motorcycle are:
Cast Wheels:
150/80R17M/C 72H
front
DUNLOP D251F
180/70R16M/C 77H
rear
DUNLOP D251
radial, tubeless
type
Spoke Wheels:
150/80-17M/C 72H
front
DUNLOP D404F
170/80-15M/C 77H
rear
DUNLOP K555J
bias-ply, tube
type
120
Servicing Your Honda
Whenever you replace a tire, remember:
Have the wheel balanced after the tire is
installed.
Have the tire replaced by your Honda
dealer if possible.
Spoke Wheels: Have a new tube
installed whenever a tire is replaced.
The old tube will probably be stretched.
If installed in a new tire, it could fail.
If you have a tire professionally replaced
at a non-Honda facility, we recommend
that you have the work checked by your
Honda dealer.