Looks like Tamiya is really getting into this rock crawling thing. Recently they announced a new set of 2.2″ rock crawling tires called the Cliff Crawler. The Cliff Crawlers feature a high traction tread pattern including treads on the sidewalls for great side bite. Currently the release date and pricing is not set.
more info: http://www.tamiyausa.com/product/item.php?product-id=54117