Some drivers seem to be confused about the difference between wheel alignment and wheel balance. The two are quite a bit different from each other, with differences in the driving experience as well. We’ll break down the difference in the two:
What Is Wheel Balance?
When you install a set of tires on a vehicle, the technician has to ensure that the wheel is perfectly in balance before it goes back on the car. That is done by adding a lead weight to the rim at a specific spot to make sure the wheel is balanced. Older wheel balancing machines were not much more than a jig or spindle with the wheel and tire laid horizontally across it; the tech could then add and move weight until a bubble in the middle was completely spot-on, like using a carpenter’s level.
Newer systems spin the wheel and a processor can (virtually) “split” the tire into two halves and measure the forces on each side of the tire’s center. The tech then adds weights (sometimes as little as ¼ of an ounce) at specific spots on the front or rear of the rim until the wheel is perfectly in balance.
Signs of a Wheel Balance Problem
A wheel that’s out of balance will set up a noticeable vibration; it might be just during a certain speed range, or only at highway speed, or it might gradually get worse as you accelerate. Still, it will be something that’s perceptible through the steering wheel or floorboard, and it’s pretty unmistakable. A vehicle with a wheel balance problem that’s not corrected can end up with suspension or wheel bearing issues as the vibration starts shaking other things loose.
It’s important to remember that a balance isn’t always a one-time thing. A hard hit on a pothole or railroad tracks can be enough to affect balance; in rare cases, it can dislodge a wheel weight (weights are always mounted on the edge of the rim, near the tire). Also, a tire’s mass changes as it wears down and sometimes that change in mass can be enough to affect balance. That’s why tire shops will usually recheck balance on all four tires as part of tire rotation.
What is Wheel Alignment?
Your car leaves the factory with the front wheels set at specific angles for the best cornering ability, road manners, on-center feel and overall handling. A hard hit on a bump can be enough to change those angles and knock a front wheel out of spec. The four main angles are:
- Toe-in, the angle at which a wheel’s front is skewed inward
- Toe-out, the reverse of toe-in
- Caster, the outward tilt of the top of the front wheel (as seen from the front of the car)
- Camber, the inward tilt of the top of the front wheel
These angles can all be measured, changed and reset via minute adjustments in the steering linkage, with the tech using a piece of equipment called an alignment rack.
Signs of Wheel Alignment Problems
Wheel alignment problems are pretty unmistakable and can be indicated by:
- Persistent pull to one side on straight, un-crowned pavement
- Uneven wear along the edge of one tire, caused by the tire being “dragged along” by the others as it tries to steer the vehicle in another direction
- Poor return to center after rounding a corner
- Steering feels “heavy” and clumsy
What you won’t experience with a wheel alignment problem, though, is vibration. Vibration can come from problems other than a wheel balance issue (such as worn or damaged suspension parts), but it will virtually never result from an alignment problem. You also won’t notice excessive steering play as part of an alignment issue; a lot of play in the steering wheel means there are things in the steering linkage that are worn and in need of service.
Alignment isn’t something that needs to be performed at regular intervals, but it’s a good idea to have it checked a couple of times a year. It’s also a must to have alignment checked if you notice any change in your vehicle’s drivability and handling, or if you’ve hit a pothole or bump extra hard and noticed a change.
A good alignment should take about 60 to 90 minutes, depending on the amount of work that needs to be done. It’s important to remember, however, that an older vehicle that has extremely worn front end parts (ball joints, tie rod ends, idler arm, idler arm bushings, etc) may not be alignable at all; the excessive wear and slop in those parts might mean that the alignment is off again as soon as the wheels are back on the ground. In those cases, it might be necessary to replace those parts and essentially overhaul the suspension and steering linkages before the vehicle can be aligned.