After not riding for a couple of days I checked my tires yesterday with bike on the jack/lift. Rear tire was down 20 lbs from 42 to 22. Front was good. Also checked with gauge on my Slime plug-in small compressor--same readings. Last checked/added air about 3 weeks ago. Aired up rear tire. Checked it few minutes ago, doesn't seem to have lost any air since yesterday afternoon. Would still being on the lift with tires off the ground make any difference with a small leak? Would riding cause a small leak to lose air but not riding with a small leak and NO air loss? Let the bike down off the lift--will check tires again tomorrow and will ride some then check again. Don't understand how I lost 20 lbs. of air then no air loss since airing back up yesterday afternoon.