Air1,
You might find it useful to understand the "hardness" of the tire. I believe that this property would be expressed in durometers (spelling might be wrong). A car tire manufacturer would probably happliy tell you relative to car tires, as it is a characteristic which makes summer tires, and snow tires different. Once you understand this, the aircraft tires characteristics may make more sense. Hardness would equate to friction somehow. Aircraft tires are definately not all the same!
Piper will probably not be able to be of much help with this, as they buy tires, which conform to the "TSO" standard of design and construction.
I tried to paste in a link, but it won't work. Look on the FAA website for TSO C62e. It should explain a lot...
Cheers, Pilot DAR