I just started looking into replacing the 185/80d13 LDR D tires on our Jay Feather EXP 29A and was surprised to find the lack of options available in a load rated D tire. Looking at all the options for Radial and Bias along with changing up to a 14". But, the more digging I do the more I find that the 185/80d13 (C78-13) LDR D bias tire may be the best route to go. Was thinking of going to a load range E but I can not find them in a 13". Not sure exactly which route I am going to take but yet.