Honda FOURTRAX RUBICON 2018 Owner's Manual page 197

Always check air pressure when your tyres are "cold." If you check
air pressure when your tyres are "warm" – even if your ATV has only
been ridden for a few miles – the readings will be higher. If you let
air out of warm tyres to match the recommended cold tyre
pressures, the tyres will be underinflated. Be sure to check tyre
pressure at the riding site, since changes in altitude can affect air
pressure.
The recommended "cold" tyre pressures are:
RECOMMENDED
PRESSURE
FRONT
30 kPa (4.4 psi)
REAR
30 kPa (4.4 psi)
Servicing Your Honda
Tyres
187