Give it a little bit to finish clearing the upload, but:
http://www.youtube.com/watch?v=03tYPM1Bw4c
Videographic evidence of what "standard" 4wd bots will turn like. Bot is weighted down (with about 60-80lbs on the bot and some unknown amount on the trailer).
Before anybody asks, yes, our tile flooring is similar to the regolith. We had a mentor who works for 3M bring in their version of Regolith and we did traction testing (tile floor vs. 3m "regolith" and we got the same results, 10lb breakaway force, 8lb dynamic pull @60lb 2wd robot).
(What you don't see, after the video: The robot's wheels just about fell off and it took a good hour or so to get them working completely again. Oh, the joys of thrown-together prototype bots)