I think gaijin is correct. Since I elected to install P-Metric Toyo AT2 in the 285/70-17 size my radius went up but the overall weight is within a pound of the OEM 18" set. Small impact on acceleration, negligible difference in braking effectiveness and perhaps one MPG hit on fuel. Noise up slightly. Everything matches anticipation. You can simulate the acceleration impact by selecting 2nd gear start.While the decreased performance you note is certainly true (I notice the same with my 285/70-17's compared to stock), I would suggest it is more due to the increased diameter of the tire than the weight.
HTH