Lead/pull is the deviation of the vehicle from a straight path, on a level road with no pressure on the steering wheel.

Lead/pull is generally caused by the following conditions:

The way in which a tire is built can produce lead in a vehicle. An example of this is placement of the belt. Off-center belts on radial tires can cause the tire to develop a side force while rolling straight down the road and the tire tends to roll like a cone.