The European number is 37-590 and you can buy them at most outlets. Examples would include Ace Hardware, K Mart, Wal Mart and so on. None of the Mt. Bike style tires will fit as those are 559 diameter tires not will Schwinn 26 x 1 3/8 which are 597 diameter. Those European numbers will be on the tire in the same place the 26 x number is. Remember you need 590 tires which is the actual rim size. Roger