ok first of all driving on road and off road are two different settings for pressure.
for onroad, the difference in front and rear is not really noticeable between 2.4 and 2.7
usually they pump more air in the back if u need to load the trunk with stuff, or to accommodate 3-5 people in the back.
if u really really want to get the exact pressure u should be at, try this:
get a blackboard chalk and draw a line across the tyre width. drive for a few meters and notice where the chalk is still on the thread and where its started to disappear.
if its removed at the sides, then its underdeflated,
if its removed at the middle only, then its overinflated
if its worn perfectly evenly from side to side, then ur at exact pressure.
for offroad, it completely depends on the terrain, but sometimes u may need to deflate to 0.7 bar even.