Hard to beat US421 when you're coming this way. There are certainly more convoluted routes but 421 is easy to follow and quite entertaining. Goes to Bristol rather than directly to Maryville but if you're going to be down here and you're into famous motorcycle "destinations" you really should ride "The Snake" around Shady Valley, TN. Make a route from Mountain City across the mountain to Robbinsville, NC and approach Deals Gap on US28. Much better than the highly populated Knoxville/Maryville side.