It depends on the air pump connection how much air you'll actually lose. With the lever type connections, it seems you lose more air than with a screw on/off type of connection. I've always inflated my tires ( especially the rear tire to about 105 more PSI than what the sidewall pressure guide recommends. My 700c X 35mm tires call for about 5 bars or 70/72 PSI. I usually pump them up to about 80 PSI because in about two weeks, they'll lose that extra air and be right at 70/72 PSI. You can always let excess air escape by checking it a few times with your air gauge until you get it where you're comfortable with the reading.