Alignment Angles Explained: Camber, Caster and Toe

The three angles on an alignment printout, what each one does to steering and tire wear, and which ones a pothole or a lift is most likely to move.

An alignment printout shows three angles per wheel with red and green numbers, and most people are handed it without an explanation. The three angles each do a specific job, each wears a tire in a specific way when it is wrong, and each is moved by specific kinds of damage. Understanding them makes the printout useful.

Toe

Toe is whether the front of the tires point slightly inward toward each other (toe-in) or outward (toe-out), viewed from above. It is measured in fractions of a degree or in fractions of an inch. It is the angle that wears tires fastest when it is wrong, because a tire that is not pointing straight down the road is being dragged sideways slightly with every rotation.

• Wear pattern: a feathered edge across the tread, sharp on one side of each block and rounded on the other. Run a hand across the tread and it feels smooth one way and rough the other.
• Symptom: often none from the driver seat until the tires are ruined. Sometimes a wander or a vague steering feel.
• Moved by: a pothole, a curb strike, a bent tie rod, worn tie rod ends. Toe is the angle most easily knocked out and the one most often adjusted.

Camber

Camber is the tilt of the tire viewed from the front. Top of the tire leaning outward is positive camber; leaning inward is negative. Most vehicles run a small amount of negative camber for cornering grip. Too much either way loads one edge of the tread.

• Wear pattern: one edge of the tread worn smooth while the rest is fine. Inner edge for too much negative, outer edge for too much positive.
• Symptom: a pull toward the side with more positive camber, and uneven wear you can see.
• Moved by: a bent strut, a bent control arm, worn ball joints, a sagging spring, and any change in ride height including a lift or a heavy constant load. Camber is often not adjustable from the factory on trucks, and correcting it can mean a cam bolt or a replacement part.

Caster

Caster is the tilt of the steering axis viewed from the side, like the angle of the forks on a bicycle. Positive caster makes the steering self-center and the vehicle track straight at speed. It does not wear tires much on its own, but it is the angle that decides how the vehicle feels.

• Symptom: with too little caster the vehicle wanders and the steering feels light and does not return to center after a turn. With caster uneven side to side, the vehicle pulls toward the side with less.
• Moved by: a lift or leveling kit, which drops caster on most trucks; a bent control arm; worn bushings; a shifted subframe.
• Adjustment: often limited or not adjustable from the factory, which is why lifted trucks may need aftermarket arms to get caster back.

Thrust angle and rear alignment

Rear wheels have toe and camber too, and on many vehicles they are adjustable. The thrust angle is the direction the rear axle is pointing relative to the centreline. A rear axle pointing slightly to one side makes the vehicle drive slightly sideways, the steering wheel sits off-center to compensate, and the front tires wear even after a front alignment. A four-wheel alignment measures and corrects this; a front-only alignment cannot.

What a good alignment includes

1. 1A check of tire pressures and a check for worn steering and suspension parts first. An alignment on worn parts is out of spec by the time you leave the lot.
2. 2Measurement of all four wheels.
3. 3Adjustment of what is adjustable to the manufacturer's specification, not to a generic figure.
4. 4Centering of the steering wheel.
5. 5A printout with before and after numbers.

How that relates to balancing, which people often confuse with alignment, is in balancing versus alignment. And steering off-center after a pothole covers what to do when the angles moved suddenly.

Frequently asked questions

How often should alignment be checked?

With every new set of tires, after any suspension or steering repair, after a hard impact, and any time the tires show edge or feather wear. On trucks that run caliche and washboard, at least once a year.

Can alignment cause a vibration?

Rarely. Vibration is balance, a bent wheel or a tire problem. Alignment causes pulls, wander and wear.

Why is my alignment out again after a few months?

A worn part that was not replaced, or roads that keep knocking it out. Ask to see the parts inspection from the last alignment.

Alignment checks and steering and suspension repair are done in our bays at 13209 Frankford Ave, Suite 29, Lubbock, as part of the full mechanic shop. Call (806) 458-2709. Drivers make the trip in from Ralls and across the South Plains for it.