While nosing around the other day I noticed a couple of XLV Marathons with XZA2 315 tires. Seems I usually see ZXA1 mounted on XLV, that is what I have mounted on my bus. What is the a difference between the two? I have heard the 1 is getting harder to find, and the tread is the only difference and also one person said the 2 has a softer sidewall. 3 guys 3 opinions--imagine that. What is the real story?