What Solitude says. Don't mess with the canned "sealer" fix-a-flat crap. Slime all your tires now and pick up the Slime tire repair kit that comes with plugs, more slime and a handy compressor. The compressor works great, I used mine to air up the huge front tires on an M35A2 recently acquired.
http://www.slime.com/product_281_Pow...t_(70004).html
Slime is great stuff, non-flammable, and you can leave it in there before you get a flat. I use it in all kinds of stuff like my mower tires, presta bicycle tubes, tractor tires, truck tires, especially where I'm likely to get punctures like off-road or heavy brush. Then again I buy this stuff by the gallon!
Got a roof rack? Excellent place for full-size offroad spare. Just like Marlin Perkins!