Like Steve said, it sounds mis aligned to me too. I have a california sidecar that weighs 225 lbs, with a 13" 155 car tire on it, and I run around 35 psi in the tire. after about 7K miles, I still cant tell there is any wear on the tire at all, it still looks new.
I bet you have too much toe in, or worse, toe out, and its causing the tire to "scrub".
I only run about 1/4" toe in on my rig.