I have 6" rims on my 40's vintage hand-built micro car. The tires are listed as 14x4.50-6 (they are tube tires). I cannot find a "street" tire in this size (found tractor tread and rounded mini-bike tires). I have found tractor tires "not for highway use". Does anyone have a suggestion of where to find them? Coker website cannot help. I've been restoring for nearly a year, and the tires are dry-rotted.