Last year I decided to invest in some Slime ( www.slime.com ) filled inner-tubes for my mountain bike. Slime is a green liquid substance which you put inside tyre tubes to prevent punctures, when you do get a puncture the green ooze comes out and solidifies. The thing is, you don’t really know whether or not it is working because you aren’t sure whether you have just been lucky enough to not have a puncture, or if the slime was doing its job. Now I know and I’m glad I bought them. I fitted some new tyres this morning (Continental Travel Contact) and while changing them I noticed a couple of huge thorns going straight in to the tubes… there was green gunk inside the tyre where it had leaked out, but also a nice little green plug blocking both punctures. Thorns removed and tubes patched just in case, then on with the new tyres. I decided on hybrid style tyres (smooth with chunky edges) this time instead of heavy duty mountain bike ones, and again I’m glad I did.. an average speed increase of 25% and it is so much easier to keep the speed up. These ones are kevlar reinforced and have a one year anti-puncture guarantee. Combined with the Slime tubes I’m hoping they’ll be pretty invinsible.