Why is alignment important? Proper alignment helps ensure that your vehicle handles correctly and can increase the life and performance of your tires.
When to Check Alignment?
Daily impacts such as potholes and railroad crossings, as well as more severe events like accidents, can knock your vehicle out of alignment. Have the alignment checked if any of the following happen :
- You’ve hit something.
- You see a wear pattern developing on the shoulders of the tires.
- You notice a difference in your vehicle’s handing.
How Wheels Are Aligned
Alignment involves adjusting the angles of the wheels so that they have the proper toe in and camber. The three main adjustments made in alignment are camber, caster, and toe.
Camber
Camber is the angle of the wheel when viewed from the front of the vehicle. If the wheel leans too far, uneven wear occurs.
- Positive camber is when the top of the wheel is leaning away from the car. Too much positive camber wears tires on the outside.
- Negative camber is when the top of the wheel is leaning in toward the car. Too much negative camber will wear tires on the inside.
The camber angle is designed and adjusted for each vehicle to keep the tires flat on the ground during a turn. If there is too much difference between the camber settings on the front wheels, the vehicle tends to pull sharply to one side.
Caster
Picture a caster wheel found on furniture or a shopping cart. When you push a shopping cart equipped with caster wheels, it tends to roll in a straight line because the wheels line up.
On a vehicle, a caster is the forward or rearward tilt of the steering axis, measured from the top of the tire, as viewed from the side. The axis is formed by extending an imaginary line through the upper and lower steering knuckles. The line extends through the upper and lower ball joints on vehicles with front control arms and through the lower ball joint to the center of the strut mount on cars with struts.
- Positive caster occurs when the angle is toward the rear of the vehicle. Positive caster makes your front wheels act as if your car is being pulled from the front so that they line up behind the point of pull, like a child’s pull toy.
- A negative caster occurs when the angle is to the front of the vehicle.
The caster is set so that your vehicle tends to go straight ahead. Caster affects your vehicle’s low-speed steering and high-speed stability, as well as how well your vehicle drives in a straight line (on-center feel). A negative caster will cause your car to “wander” and make it feel unstable at high speeds. Positive caster causes hard steering and can also result in excessive road shock and shimmy. Caster does not affect tire wear.
Toe
Toe is the difference in the distance between the front of the tires and the back of the tires. Toe settings affect the handling characteristics of a vehicle while turning.
- Toe-in is when the front ends of the tires are closer. Toe-in introduces understeer going into a curve. If the tires are toed-in too much, the tread will be “worn” off, starting from the outside edges.
- Toe-out is when the rear ends of the tires are closer. Toe-out can introduce oversteer in a curve and makes the vehicle feel like it is “diving” into the turn sharply. If tires are toed-out, the wear will start from the inside. This type of wear is called “feathering” and can be felt by running your hands across the tread of the tire.