ZERO TOE "Zero" toe is when both wheels are aimed straight ahead and are parallel to each other, parallel to the vehicle centerline, and perpendicular to the axle. Zero toe is the ideal alignment setting and will produce the least amount of rolling friction and tire wear when the vehicle is in motion.
TOE-OUT "Toe-out" is when the leading edges of both tires are further apart than the trailing edges. The tires are not parallel to each other or the vehicle centerline, and are not perpendicular to the axle. Too much toe out is an undesirable condition because it causes the tires to scrub sideways as they roll. This increases friction and tire wear.
TOE-IN "Toe-in" is when the front edges of both tires are closer together than the rear edges. Too much toe-in is also an undesirable condition because it also causes the tires to scrub sideways as they roll. This increases friction and tire wear.
TOE SPECIFICATIONS The toe setting may be specified in inches, millimeters or degrees (the angle between the tires). Most alignment specifications are for "total" toe, which is the difference between the leading and trailing edges of both tires with respect to one another. Some toe alignment specifications (primarily for rear toe) may specify "individual" toe, which refers to the toe setting of each individual wheel with respect to the vehicle centerline.
TOE WEAR Toe has the greatest effect of any alignment angle on tire wear. If the wheels are toed-in or toed-out more than specifications allow, they will wear rapidly and unevenly. Toe wear usually appears as a feathered wear pattern across the tread and/or shoulder wear on the inside (toe-out condition) or outside (toe-in condition) edges of the tires. Both front tires will show the same kind of wear if toe alignment is out of specifications. The same is true on vehicles that have adjustable rear toe. The ideal situation is to have zero toe while the vehicle is traveling down the road. But to achieve perfect toe alignment, compliance in the suspension bushings and steering linkage must be taken into account. The normal play in the linkage plus the compression that occurs in rubber control arm bushings allows toe to change slightly when the vehicle starts to move. The front wheels tend to toe-out in rear-wheel drive vehicles because they are being pushed down the road. This compresses the bushings and linkage. Because of this, most rear-wheel drive vehicles require a slight amount of toe-in (1/16 to 1/8 in.) to compensate for suspension compliance.
With front-wheel drive, the front wheels tend to toe-in when accelerating because the front wheels are pulling the weight of the vehicle. This occurs because drive torque makes the wheels want to turn inward on their pivot points. This stretches the steering linkage and compresses the control arm bushings in the opposite direction. As the car reaches a stable speed, drive torque and rolling resistance may offset each other allowing the wheels to return to a neutral or zero toe setting. When the brakes are applied, the wheels are pushed back causing them to toe-out. Most front-wheel drive cars require zero toe or a little toe-out (1/16 to 1/8 inch) to compensate for compliance.
If the toe setting is out of specifications, or the front or rear tires show signs of toe wear (feathered wear pattern and/or inside or outside shoulder wear), toe alignment needs to be checked along with the condition of the tie rod ends and other components in the steering linkage and suspension to determine the cause.
NOTE: Don't confuse camber wear with toe wear. If only one front wheel shows heavy shoulder wear on the inner or outer edge, the problem is not toe misalignment but camber misalignment (SEE CAMBER).
Worn tie rod ends, inner tie rod sockets (rack & pinion steering) or collapsed control arm bushings are common causes of toe misalignment and toe wear on the tires. If worn or damaged parts are found, they must be replaced prior to resetting toe alignment back to specifications. Worn or damaged parts cannot hold an accurate alignment setting.
Page 1 If the front tires show toe wear, but front toe is within specifications, the underlying cause may be rear axle steer (see THRUST ANGLE). Rear axle misalignment can cause the steering to pull to one side. This causes the driver to compensate by steering slightly off-center to the opposite side. But when the wheels are turned, even slightly, either way off center it causes the front tires to toe-out slightly (SEE TURNING ANGLE) resulting in toe wear on the front tires.
Toe problems can also be caused by bent parts such as tie rods or steering arms. Measuring the distance between each control arm and wheel is one way to make sure both are the same. If there is a difference, one of the arms is bent. Comparing measurements to another vehicle of the same year, make and model can help you figure out which arm is bent. Pulling down the suspension and checking for uneven toe changes side-to-side is another "trick" that can be used to check for hidden damage such as bent parts or a steering rack or linkage that is not parallel to the road.
CORRECTING TOE Front toe is adjusted by turning the sleeves on the tie rods to change their length, or by turning the tie rods themselves to change their length.
Increasing the length of a tie rod that connects to a steering arm behind the knuckle will decrease toe and cause the wheel to toe-in. Shortening the length of a tie rod that connects to a steering arm behind the knuckle will increase toe and cause the wheel to toe-out.
If the steering arm is located ahead of the knuckle (some trucks), changing the length of the tie rods will have the opposite effect. Lengthening a tie rod will cause the wheel to toe-out while shortening the tie rod will cause the wheel to toe-in. NOTE: Before adjusting the tie rods, the steering wheel and linkage must be centered (in the straight ahead position), otherwise the result may be off-center steering and/or unequal toe changes when turning. On rear-wheel drive vehicles with parallelogram steering linkage, the length of the tie rods is changed by loosening the clamps on the adjustment sleeves and rotating the sleeve. NOTE: Right and left sleeves may be threaded differently. Remember to retighten the sleeve clamps after adjusting.
On front- and rear-wheel drive vehicles with rack & pinion steering, the tie rod end lock nuts must be loosened so the tie rods may be turned. NOTE: Be careful not to twist the bellows, and remember to retighten the tie rod end lock nut after adjusting. On front-wheel drive cars with adjustable rear toe, or rear-wheel drive cars with independent rear suspensions and adjustable toe, rear toe may be changed by altering the length of tie rods, by rotating offset control arm or linkage bushings, or by installing shims between the wheel hub and axle.