A couple of weeks ago I took a day off to work on my bikes and go for a nice long ride. I wanted to test out the new tall stem that I installed on my Motobecane Nomade, so I top off the tires and load up my stuff and away I go. Not a minute later the bike is feeling squrrely and I look down to see my rear tire seems a bit more flabby than it should. These tires and tubes came with the bike from the original owner but I don't believe their too old. Well the thing is, I topped them off at 90-psi and then when I put the pump on the dial read around 70-psi. So I topped them off again to 90 and not a minute later the bike is squirrely again and the rear tire--which now has more of my weight on it due to the taller stem--seems flabby again. I decide to scrap my ride as I had spent most of my day installing cables and cleaning up my frankenbike. I pump up and ride home and by the time I'm home again everything seems flabby. I'm thinking 'great, got a slow pinch flat right away on my dirt/gravel road'. Fast-forward 2 weeks and I look at the tires and they still have air in them??? *scratches head* I expected this to be flat like my PUCH. Can a tube get old and decide not to hold 90-psi anymore???