Originally Posted by
Crankycrank
You might also want to check out Sheldon Browns tire sizing article as 26" has roughly 4 different bead diameters. Grabbing any 26" labeled tire might be the wrong one for your rims. Kind of a long article but just scroll down a few paragraphs to the
"B.S.D." heading for a quick explanation. Explains the
ISO (International Standards Organization) sizing which is listed in metric measurements and printed on almost all tires. There are also some charts in the article comparing the different tire sizing systems to
ISO. This is the only system that tells you what the actual BSD sizes are if you are in doubt.
Tire Sizing Systems
All that is true, but 99% of the time you will bumble into the correct tire as all the sizes except ISO 559 have gone out of fashion, especially in wide. Many big box store bikes and also Specialized and perhaps others are still make bikes today with ISO 559 "Mountain Bike" rims.