Taking Care of Your Car Keeps You Safe

Why Do You Need a Four-Wheel Alignment?

17 June 2021 by Kent Alvarez

Many shops advertise four-wheel alignments as part of their routine maintenance options, but why is this service critical on many modern vehicles? If you're old enough to remember when classic cars weren't so classic, then you might also remember when you didn't need more than a two-wheel alignment. So, what's changed in the modern automotive world?

The answer relates to how manufacturers design the rear suspensions on most of their vehicles. In the past, automakers typically used a solid (sometimes known as a "live") rear axle. By contrast, newer cars, crossovers, and even SUVs now favor a fully independent rear suspension.

More Complexity, Better Handling

In a solid rear axle setup, a beam axle directly connects both rear wheels. This design is often known as a dependent design since neither rear wheel can act independently. This design offers few advantages, mostly centering around its lower cost. Solid rear axles are also somewhat more durable than their independent counterparts, making them a favored option on some off-roading vehicles.

On the other hand, independent rear suspensions allow each rear wheel to move on its own when hitting a bump or traveling over ruts in the road. This freedom not only improves the vehicle's ride quality but also improves handling. Since the wheels do not move in concert, it's easier for the vehicle to maintain traction when traveling over uneven surfaces.

The trade-off for these advantages is more complexity and more cost. These two downsides meant that many older cars used live axles for their rear suspension, but independent suspensions are now the industry standard. This more modern design is now so ubiquitous that you can even find it on some newer trucks.

Independent Rear Suspensions and Four-Wheel Alignments

When you have your wheels aligned, the shop adjusts three essential angles: camber, caster, and toe. These angles can change due to suspension component wear or acute damage, altering your vehicle's handling characteristics and resulting in premature tire wear. However, since a live axle links both wheels, making these adjustments usually isn't possible for these cars.

With more modern vehicles featuring independent rear suspensions, each wheel has its own suspension components that can wear independently. Over time, this wear can cause the individual alignment angles on each wheel to fall out of factory specifications. Hitting a deep pothole or a high curb can worsen these issues, and acute damage like this may only affect one or two wheels.

A four-wheel alignment ensures that each wheel is as close as possible to its factory alignment specifications. This approach ensures that your vehicle continues to drive as its manufacturer intended while also minimizing the likelihood of unusual or premature wear on your tires. Talk to an auto shop to get a wheel alignment for your vehicle.

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