Spindle (automobile)
In an automobile, the spindle is a part of the suspension system that carries the hub for the wheel and attaches to the upper and lower control arms. The spindle is referred to as an Upright in UK-built vehicles and in areas dominated by cars designed for the UK, like Australia, New Zealand etc.
Design
There are several considerations when designing an upright. Loads and forces need to be considered. Vertical and horizontal forces greater than those due to 5 times the acceleration of gravity, that is, about 50 meters per second per second, are sometimes considered desirable.
Non-driven wheel
The main forces on a non-driven wheel are braking and turning forces.
Driven wheel
The forces on a driven wheel include forward and reverse propulsion as well as the braking and turning forces.