Last week, at the start of a ride on the bike trail, I noticed a flat starting in the rear. When I got home and got the tube out it had a minute pinhole right about where the tread area meets the sidewall. There was absolutely nothing in the tire that would cause this. I did both a visual and tactile check of both the outside and inside. After rechecking several times, I could find nothing poking through or sign of anything having been there.
Went out again last Sunday, and after about an hour, same thing. This time, there were three pinholes and one that almost looked like a small cut. Most of these were at the top of the thread area of the tube. I again thoroughly checked the tire and could find nothing.
Both Marathon Racers and Schwalbe tubes are new, with maybe a half dozen shortish rides on them. And it's only the rear having this problem. I take proper precautions when installing, including the use of a Kool-Stop Tire Bead Jack to avoid pinching.
Guess I should just go back to cheap tires and thorn proof tubes with Tuffys. Any reports of Schwalbe counterfeits?