I just bought a used tow dolly, brand is unknown, however it has a heavy frame and beefy tow arm, about 50% more bulk than master tow. I'll be towing my wife's Murano mostly on I-95, in Florida, for 170 miles one way between our two homes. The dolly has two radial tires a 175/70R-13 and and 175/80R-13. There is plenty of rubber left on both of them and I'm not concerned about the ratio, that but I do need a spare. There are the bias ply (D rated) and radial. Does anyone know if the radial is any better than bias ply for trailer-ing? I might get two new bias ply tires and used the radials as spares, or get one radial (/80R) and use the /70R as the spare.