How do I tell if I have tubulars on my rim? There is no identifacation on the existing tires. They are 700 x 20's, about the size of your thumb! and are holding air real good. I intend to replace them with 700 x 28's. The alloy rims have nipple inserts. Yeah I know , take 'em off and see!!! Then the question do I have to stick with tubulars. Thanks guys