When a rear-wheel drive truck goes up a hill, do its rear wheels gain traction because of a transfer of weight to its rear wheels? I think it depends on the center of gravity, right? — DA, Issaquah, Washington
The traction a wheel experience depends largely on how hard it’s being pushed into the roadway. When the truck is on level pavement, the roadway prevents the wheel from sinking into it by pushing upward on the wheel with a force called a support force. Because a wheel’s traction is roughly proportional to the support force it’s experiencing, the harder the wheel is pushed into the roadway, the more traction that wheel has.
Since a truck has its heavy engine in front, the front wheels bear more of its weight than the rear wheels and they experience more traction than the rear wheels. But as the truck tilts upward on the hill, the weight of its engine is born more and more by the rear wheels. In physics terms, the truck’s center of gravity, which is almost over the front wheels while the truck is level, shifts to be more and more over the rear wheels as the truck tilts upward.