Originally Posted by
Crankycrank
My first guess would be that the tube was pinched under the tire bead when mounting but if not mounted recently and ridden a few miles then this is not the problem.
Pinched by the tire? They are both wire bead tires and I had just mounted both (they are old but different sizes and I wanted to check to see what clearances my frame has, so I took them off and put them back on again without riding). I didn't use levers to install them. The tires are very old, the tubes probably are too but I'm not sure.