Has anyone thought about using space saver spare rims and tire for trikes? I haven't looked at one for a while but I think they're DOT approved tires. Finding DOT tires for narrow tired motorized vehicles that qualify as motorcycles is a major issue, since bicycle tires don't qualify. They also have flat tread sections so they have a great contact patch with the road. Motorcycle tires have near hemispherical treads which don't provide a great contact patch for three wheelers. Space savers come with steel or metal rims which were meant to hold up a 1 ton to multi-ton vehicles. They're not going to flex when cornering on anything we're likely to use them as primary tires. They're rated up to 50mph. A speed motorized bikes are not likely or legally supposed to come close to achieving. In college in the late 80s I had a 1980 Datsun 200sx, it had 185/70-14s and had a space saver which I think was 90/170-18. It's been a long time. The only problem might be finding a pair of the same size if they're from really old vehicles.