Mine is currently at 40 psi (rear) and 36 psi (front). Too high tyre pressure equals bad road grip. Finding the correct pressure will depend on the total weight you are carrying, ie your weight plus any luggage / passanger, as well as the road conditions to be used on.
Something you can test for yourself, after a ride, feel the tyre for heat with your hand. If warm, then pressure is correct but if hot, the pressure may be too low. Try it for yourself by lowering the tyre pressure a few psi and following the steps above. Remember to inflate tyre when cold or else you may end up with wrong pressures.