What Are The Pros And Cons Of A Torsion Beam Suspension?

Much like muscles and tendons working together to absorb shock for the human body, or how running shoes cushion impact with each stride, a car's suspension combines carefully designed components to tame the world's imperfect streets and highways in the name of safety, comfort, and performance. Engineers have come up with several approaches to suspension design over the years, each with different cost, complexity, and packaging considerations. These factored directly into why Mazda elected to utilize a torsion beam rear suspension when it redesigned the current Mazda 3 platform in 2019.

Regardless of where a vehicle will be driven, getting suspension settings right is a crucial mixture of art and science that starts with choosing what type of suspension design to use. Some vehicles, like Jeeps, are famous for being engineered to conquer the roughest terrain, while Formula One racing suspensions are designed to safely extract every last ounce of speed within the limits of drivability on the racetrack. Torsion beams, though less sexy than their sophisticated multi-link counterparts, are simpler rear suspension designs that can offer lower weight and costs, and free up valuable passenger or cargo space — in exchange for potential dips in ride tuning and customization.

Murphy's Law says that whatever can go wrong, will go wrong. Murphy would probably dig torsion beams for their simplicity. Where the rear wheel hub and brake assembly meet the car, a common multi-link suspension setup features a combination of parts, from upper and lower control arms, to shocks, springs, and connecting rods, on each side. That's 10 components — plus an anti-roll bar that runs between the wheels for lateral stability.

In contrast, as pictured above, a torsion beam basically has five major components — total — including an H-shaped frame to mount the springs and shocks, and trailing arms with bushings to hitch up to the chassis. The beam part spanning that H gives the torsion beam its name, and effectively fuses the right and left sides of the suspension together.

In our age of alternative facts, let's choose to agree that five parts is less than 10 parts. From a reliability perspective, that's 50% fewer potential failure points to worry about and maintain — not to mention reduced production complexity, lower costs, and fewer parts to tune and optimize for reasonably enjoyable and safe driving.

The compact packaging also helps free up sweet interior volume for passengers and cargo. Torsion beams set the assembly comparatively lower in the chassis, and push the springs and shocks further out to the sides of the car — and that means more interior space for golf clubs, child seats, pets, and big box runs.

Tuning a suspension's complex symphony of parts to our liking is one of our readers' favorite car mods. All that complicated joinery in a multi-link setup — with so many variables in springs, bushings, shocks, adjustable end links, and stabilizer bars — lets each wheel move on its own, and lends itself to a host of modifications that can radically alter a suspension's geometry and performance. It's a (potentially expensive) playground for customization that torsion beams can't match.

With a torsion beam setup, suspension tuning options are pretty much down to the basics: bushings, springs and shocks. This modification constraint may liberate or frustrate, depending on your perspective. As much as enthusiasts love to geek out over lowering springs or the difference between shocks and struts, we can only go so far, because we can't change that factory-installed torsion beam spanning the car's rear. Hence, the right and left wheel actions are never fully independent.

That doesn't mean torsion beam suspensions can't yield track stars. Volkswagen ran them for ages on Golf GTIs, also known as the great granddaddy of hot hatches. Nor does it mean that ride harshness is the rule with torsion beams; as Mazda's torsion beam work on the recent 3 shows, factory engineering wizardry can lead to a great ride. Ultimately, then, the biggest con of torsion beams is tied to whether you intend to customize your car's performance, and how much standard cushioning you consider customary. If it's a cushy air ride you're after, you may want to check out the pros and cons of air suspension.