Quote Originally Posted by SadieKate
Clinchers use tubes. Tubulars (aka sew-ups) do not.
Sew-ups do use tubes. When you repair them, you have to open the stitching and patch the tube. But you can't replace the tube (unless you want to do several hours worth of sewing). You don't carry spare tubes, but a spare tire with a tube sealed inside. There are new tires called "tubular clinchers" which contain no tubes and use clincher rims. Traditional sew-ups use a very different rim and are held on by glue.