Originally Posted by cyccommute

I've found that the older the liner, the less likely it is to cause an abrasion flat. All of my flats from abrasion by the liner have been with new liners. I would also avoid the "Slime" brand liners. Those cut through tubes like a hot knife through butter.

I've run Mr. Tuffy's for ages in my tires without problems. They work quite well against goatheads...not perfectly, but well enough. Liners are somewhat superfluous now since so many tires come with them already...they are under the rubber of the tire. That's one of the reasons that many tires like the Schwalbes are so heavy.