Originally Posted by
datlas
A tubeless tire essentially has rubber (not sure if butyl but prolly or equivalent) bonded to the inside of the tire.
Kind of, but not really. There are tubeless tires and tubeless ready tires. Tubeless tires are the ones with the impermeable lining that doesn't require sealant - I don't know that I've actually come across one of those IRL yet. Tubeless ready tires seem to be much more common (at least among the performance tires that I've been using), require sealant for normal use and aren't that much heavier than their tubed counterparts.