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

Lead is caused by:

The way in which a tire is built can produce lead in the 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. If one side of the tire is a little larger diameter than the other, the tire will tend to roll to one side. This will also cause the tire to develop a side force which can produce vehicle lead.

1. Part of the lead diagnosis procedure is different from the proper tire rotation pattern currently in the owner and service manuals. If a medium to high mileage tire is moved to the other side of the vehicle, be sure to check that ride roughness does not develop.
2. Rear tires will not cause lead.