If the rubber around the hole was clean before you applied the rubber cement, then the patch should hold just fine. OTOH, if there was a thin coat of slime, it's hard to believe that it would stick. If I were you, I'd be carrying a couple of spare tubes for a while when you're using this patched one.daniell said:I recently flatted on a self sealing tube. The holes were actually small, but the tube did not seal. The chemical oozes out around the holes. I patched the two holes. Can I expect the patches to hold, or will the chemical prevent a permanent bond?