The most common 26” tire is the mountain bike tire, they have a bead seat diameter of 559 millimeters. Not all tires that are called 26” are interchangeable. If your bike isn’t a mountain bike you’ll probably need one of the other bead seat diameters. Tires referred to as 26” can have a bead seat diameter of 559, 571, 590 or 597. We have the 571’s in our 650C section, the 590’s can also be found in the 650A section and here in the 26” section with the more common 559 mountain bike size. If you get a tire with the wrong bead seat diameter it just won’t fit on your rim, no matter how hard you try. If you need help determining which tire you need please see the helpdesk and send us your question.