Steering - Pull/Drift: Overview

Classification:
FA00-001b

Reference:
NTB00-037b

Date:
June 14, 2001

STEERING PULL DIAGNOSIS AND REPAIR (REVISED)

ATTENTION:
This bulletin has been revised.

The information in the Service Procedure section was updated.

Please discard paper copies of NTB00-037a.

APPLIED VEHICLES:
All Nissan

SERVICE INFORMATION

Customers may use the term "vehicle pull" to describe a number of different potential incidents. This bulletin discusses some of the possible situations they may be attempting to describe, and provides diagnostic and repair information for each, should one occur.

In some cases a vehicle may drift to one side of the road as a normal result of road crown. Most roads in the United States are built with a "crown" to help rain water drain from the road surface. The slope of the road crown varies from place to place. In most cases the crown slopes from 1 to 1.5 percent to the right.

Vehicles have a natural tendency to drift to the low side of the crown. The greater the slope of the crown, the faster the vehicle will drift in that direction. Tires and vehicles are designed to counteract the effect of typical road crown, typically with a small amount of counteracting left pull, but may not fully counteract the effect of a highly crowned road.

Some freeways slope to both the left and right (from the center). A vehicle may exhibit a small amount of pull to the left when driving in the left lane of a freeway with this condition.

This bulletin does not address "repair" of road crown incidents because they are not vehicle related. Use the information provided in this bulletin to identify and repair other types of "vehicle pull".

Incident Description:

Pull

The vehicle consistently drifts to one side while driving at a constant speed (60 MPH) on a straight, flat road. A vehicle is said to pull if it completes a lane change in less than 7 seconds with no steering correction from the driver when driving (at 60 MPH) on a crown-sloped road of less than 1 percent. All four wheels must pass into the other lane during this time (7 seconds).





Pull can occur as a result of incorrect wheel alignment, tire condition or steering rack sliding force. It can also occur as a result of excessive tire "conicity". This refers to a condition when the tire tread surface is not parallel to the axle centerline (see Figure 1). Conicity occurs during the manufacturing process and the tire may not show noticeable tread wear. When it occurs, it has the effect of the tire taking the shape of a cone. As a result, the tire has a tendency to roll towards the point of the cone.

The vehicle will pull in the direction of the tire with the greatest conicity. If the tire conicity is equal on both sides of the vehicle, there is no effect on vehicle pull.

Steering Wheel Off-Center





The steering wheel spokes are tilted to the left or right (see Figure 2) when driving straight ahead on a straight flat road. Although the vehicle does not pull in either direction, the customer may perceive that the vehicle pulls because it will respond if he or she tries to bring the steering wheel back to center. This condition will occur if the toe-in is out of adjustment causing the tie rod length to be uneven from side to side.

Wander





The vehicle has a tendency to drift to the right or left depending on road surface conditions. Wander can occur as a result of too little caster (incorrect wheel alignment), steering rack Sliding Force setting or incorrect road wheel offset. See figure 3

Pull When Braking

The vehicle consistently drifts to one side when the brakes are applied. This condition can occur as a result of excessive play in suspension bushings or components, or because of uneven braking force.

CLAIMS INFORMATION

Please reference the current Nissan "Warranty Flat Rate Manual" and submit your claim(s) using the Operation Code (Op Code) or combination of Op Codes that best describes the operations performed.