Between those sizes, and considering the Dextar wheels you mentioned, the 215/85/16 or a 235/85/16 would be a much better choice than the 255/85/16. The 255/85/16 would really need at least a 7" wide wheel, or preferably an 8", in order to provide proper fitment for best handling and load carrying performance. The 6' wheel is simply too narrow, and can lead to very poor handling, mainly severe wander at higher speeds.
