Ok this may have been asked before and I missed it when I searched for it.  I have a 99 Coleman Niagara.  Load range c tires are at there max load.  I would like D rated tires however I am  trying to find a D rated tire in the size of 185/80R13 and a radial.  I see them in bias but cant seem to find them in radial. Or do you guys think the bias will be fine.  I just have read that for tires on the road a lot that radial is the way to go because they track better and don't heat up as much as bias because the weight on the sidewall is transferred to the thread.  Any advice is appreciated.