It's weird, shifty, cuz Schraeder valves are the easiest to put Slime IN, but the worst about clogging up with the stuff! I've never had a presta valve gunk up on me. As far as "eating away" at your inner tubes, that's some deep doo-doo. I'm sure there's a lawyer somewhere that would LOVE proof that Slime makes a product that messes up what it's supposed to fix, meanwhile putting the user's safety at risk! Urban legend, imho.