[LSxcellent]

Nah, your friend is misunderstanding the situation...

If both tires have equal traction (ie going straight down a road) then they both contribute to forward motion.

If you bias one wheel with more traction (ie shift more weight onto it, either by turning or by sitting on that side of the car) then the other wheel will slip first under heavy load.

So, if you SIT in your car, you add XXXlbs to that side, and in the USofA this is the left side of the car, so that tire will have more traction, and the result of this is the right wheel will slip first.

Both wheels contribute to forward motion no matter what, but under the WORST conditions the WORST happens.... the wheel that has the MOST grip usually gets the LEAST torque (as a result of 'differential drive' action).

This is why you need either a limited slip diff or a good traction control system (like the new Dynamic Traction Control on the new Caddilac CTS-V). These systems detect when the Unloaded wheel (ie least traction) spins, and reproportions torque to the Loaded wheel (and it does this by clamping down on the Unloaded wheel, redirecting the torque to the other side).

So basically your friend is wrong, but its not a simple yes/no question anyway.

~LSx