It's worth noting that for a fully loaded semi, the tractor weighs
only ~ 18% of the total (15,000 lbs vs 80,000 lbs). Stability comes
from the fact that the weight of the trailer is carried just ahead of
center between the two drive axles insuring weight on the steering
axle for directional control and braking.

All things being equal, proper weight distribution and good vehicle
dynamics are more important than the overall heft of the tow vehicle.
All things are rarely equal though and a heavy tow vehicle will
compensate, to some extent, for lousy weight distribution and poor
vehicle design. This is why I choose to tow with a V8 pickup. I do
feel guilty about the fuel burn but, so far, the perceived advantages
of the heavy vehicle win out. Did I mention that the pickup is paid
for......

Ray Warshaw
1LK