Putting used tubes in ew tires usually doesn't work out as the tires stretch with use and expand. The tube of course also expands so when this extended tube is put in a dimensionally correct tire it folds or creases and will eventually fail on the creases especially if it old. Another problem with old tubes, which are usually found on trailer wheels, is that when the tire is disassembled from the rim you have to lift the valve stem to get it to exit the slot in the rim and then do it again when the tire is put back together so you have 2 chances to start a leak at the base of the valve stem.