Originally Posted by Shake-N-Bake
He tows a pretty heavy fifth wheel and his SRW truck is pretty squeemish going down the highway. My SRW truck is fairly rock solid (by comparison) so I presume the difference is the sidewall rating of E compared to his rating of D.
A reasonable assumption, provided you are running the same sized tire with the same air pressure under similar loads. Typically a "D" tire will only be rated for 50psi max air pressure where the "E" has a max inflation rating around 80psi.