I suppose the question is: how deep does that hardening go? I have no hard evidence on that, though my tire guys say it is only skin deep -- as soon as you run on clear asphalt or concrete, the hard skin is worn off.


I have done that on occasion. As you say, there is a cost in fuel efficiency. Handling is affected also, though not so much that a capable driver cannot compensate. It helps to increase the tire pressure to the maximum listed on the tire itself. Still, it is a compromise, and from a survival point of view, tires are a terrible place to compromise.