Tires vary in the thickness of the liners as noted above, but they also very in how soft the rubber is. A tire with softer rubber will have better traction, but also have more flats. I bought a Trek XM 700+ which came with very soft tires and got 3 flats in the first 175 miles. I called Schwalbe about this and they said Trek spec'd the original tires to maximize traction, but they recommended a tire just below the one on the above web site that had harder rubber on the surface, but was not as puncture proof as the plus model. I bought these and have been happy with them through 1100 miles. I can't tell any difference in traction but it is a relief to get away from so many flats.