I'm curious myself Scrub, hence the reason I asked "why"? And you touched on some of the reasons CTL rubber track machines are what they are...high speed production machines. For their size and weight they can flat out do some work. With that said, there has to be a reason why someone would desire to replace the rubber belts with steel tracks. Without knowing and rather to wager a guess, I suppose it would be the material the machine is working is chewing up the belts, maybe rocky terrain. Which is a valid argument. However, if that's the case, again why I ask the reason why, steel tracks, track chains, bottom rollers in no way can match toe to toe with rubber tracks when it comes to speed of travel, which is what CTL's do. Case in point, Komatsu produced crawler dumpers, the CD60, with steel tracks, and they produced them with rubber tracks as well. I've had experience with both. That machine shares a similarity with CTL machines, that is, they do a lot of traveling. Unlike an excavator planted and digging dirt, with the CTL and the crawler dumper, if they ain't walking they ain't working. In my experience with the Kommie dumpers, steel compared to rubber track undercarriage, the steel track dumpers eat undercarriage from doing so much walking, track chains and bottom rollers most notably, whereas the rubber track undercarriage last much much longer. Yes, rough rocky terrain can cut, split, destroy rubber tracks, but in the long haul, the undercarriage for steel tracks moving at speeds of a CTL will chew into the wallet as well. I'm curious as to the experience of others on this issue.