slime is a good thing in mtb tires, in my opinion. I have slime in my commuter (mtb) bike. I wanted slime in my road bike tires, but for some reason they couldn't get it to go in...I have 650c wheels and they said I had to use the slime liner instead. In my early riding this year, I had 5 flats on my road bike in one month...that is why I went with the slime liner. But, I recently have had 2 flats with the liners...both times a small sliver of metal penetrated tire, liner and tube....I hate flats, mainly because I can't seem change the tire on my own and get very frustrated when I try....