Wheel durability is subject to differences in use. A fairly light skilled single rider puts a lot less stress on wheels than a tandem. We have been known to rock the bike a little when standing and even at only 300 lbs proabably put a lot more than twice the stress on our wheels as zonatandem. Throw in some blasting over bumbs, rairoad crossings and other obstructions to maintain mometum and i just don't think it is a valid comparison.