You can try adding liners but nails, Staples and wire are hard to stop. The worst for me is what we call Michelin Thorns. Small pieces of steel belted radials that break off when someone lets the tire wear through the casing. Makes a hypodermic needle seem dull. But beyond that Specialized Armadillos and a bit stronger than Gatorskins. They are hard and don't roll as well in my opinion but they are tuff little puppies. I had some Kevlar, or so they said, tire liners but they are best installed at home because they are a bear to put back on if you do get a flat.