As a mountain bike mechanic, I typically recommend this to my customers...\n\nAll bike tires will come with a range listed on the side with hybrids typically being between 60-100 psi.  It is important to adjust the tire pressure to the type of terrain you are riding.  If you are primarly riding on the road, I would look to inflate the tire to as close to the maximum pressure as possible.  This will give you the best surface contact and best speed/acceleration.  If you are doing a more rail trail style where you will be on a crushed limestone style path or a packed, unpaved surface, I would recommend deflating to the middle of the range or the upper 3/4 of the range.  If you have decided to take the hybrid off road more and choose to ride a more mountain bike style terrain I would use the lower end of the range.  \n\nIt is important not to under inflate your tires because the pressure on them could cause the tube to pop or you could experience what is called a pinch flat, where your tire gets stuck between 2 rocks and pops.  But also make sure not to inflate the tire beyond capacity because you can pop the tire under too much pressure.  But by following the above guidelines, you should be good to go.