Is it true that cars with torsion beam suspensions are inferior?

Arif · Feb 1, 2021 05:52 PM

 

Is it true that cars with torsion beam suspensions are inferior? 01

If you drive an econobox, it is most likely using a torsion beam (or twist beam) setup. If you have a “premium “or “performance” car, it is most likely using a multi-link suspension setup. So, torsion beams are clearly the inferior suspension, right?

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As the name suggests, the torsion beam twists to accomodate vertical forces.

Well, cars like the Renault Megane RS and the FK2 Honda Civic Type R use torsion beam suspension setups. Even the Mazda 3 switched to torsion beam from multi-link, so they might not be so inferior after all.

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Just like every other technology, the torsion beam suspension has its own set of pros and cons.

Con - Less comfortable 

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Unlike multi-link systems, the left and right wheel are not independent of each other.

The most obvious drawback of the torsion beam setup is the dependence of the left and right wheels on each other. This is because the torsion beam is welded to the trailing arms on both left and right side.

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The solid axle with leaf springs can be found in trucks like the Toyota .

Compared to a solid axle (e.g., in a Toyota Hilux), a torsion beam is able to flex and reduce the transmitted force from the right to the left (or vice versa). Hence, torsion beams are a sort of "semi-dependent" suspension.

However, fully-independent suspension setups (multi-link) are much better when it comes to isolating road undulations.

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The forces are still transmitted, hence reducing the comfort levels of the rear passengers.

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The main benefit of independent suspension is the isolation of undulations.

The ride comfort of torsion beam setups can be improved with the design of the beam itself (thickness, welding points, shape, pivot points). More and more modern cars are adopting torsion beam designs with minimal compromise on ride comfort, but there will always be a limit for the torsion beam design.

Con - Limited design and modification potential

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The toe and camber are pretty much fixed on a torsion beam, unless you use custom washers to adjust the wheel angles (tedious).

The torsion beam suspension has limitations and when it comes to modification. Of course, this only concerns those who enjoy fiddling with their cars. With a torsion beam design, you are stuck with one camber curve. It’s rigid nature also restricts adjustment of the toe angle.

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The camber curve shows how the camber changes with the vertical wheel movement. With a torsion beam, you can't change the camber curve.

However, if designed with handling in mind from the beginning, torsion beam setups should not be an issue for those who desire spirited driving.

Hot hatches like Renault Megane RS and FK2 Honda Civic Type R have proven that torsion beam suspensions are worthy of “sports car” performance too. 

Pro – Cost

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For manufacturers, the torsion beam setup saves cost since it consists of less parts and is easier to assemble. It might actually cost more in R&D since handling, comfort, and reliability (fatigue strength), all need to be optimised for a single torsion beam piece.

As a car owner, the torsion beam is cheaper to maintain since there are only two bushings that mount the trailing arm to the chassis.

Pro - Space

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The torsion beam setup allows for a large boot space in the Proton Persona

Generally, torsion beam suspensions allow for more space in the cabin and boot. They don’t require sub-frames and anti-roll bars. That’s why they are so popular in compact saloons and hatchbacks.

Some cars are switching back to torsion beam

Besides the usual econoboxes, some notable cars that use the torsion beam setup include the Mazda 3 and the upcoming Toyota Corolla Cross.

Mazda 3 sedan front

The case of the Mazda 3 is in an interesting one since it even uses a torsion beam setup on the AWD Mazda 3. With its varying thickness of the torsion beam, the left and right side feel almost independent of each other. The comfort is comparable to that of a multi-link setup. 

Another interesting case is the torsion beam setup of the Toyota Corolla Cross. Despite sharing the same TNGA-C platform as the Toyota Corolla and Toyota CH-R, the Corolla Cross uses a torsion beam setup instead of a double wishbone setup.

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It seems the torsion beam technology has improved the years. Gone are the days of the full-on double-wishbone setup on all four corners of the first-gen Honda CR-V.

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Are all multi-link suspensions inherently superior?

Just because a car uses a multi-link setup, it doesn’t make the car superior in terms of handling and comfort. We’ve tried some cars with multi-link/double wishbone setups and some of them didn’t live up to expectation in terms of comfort.

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And when it comes to performance, hot hatches like the Megan RS and FK2 Type R show that the torsion beam setup is very capable if done right.

Besides the design, the tuning of the suspension setup plays a big role.

Summary

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Obvious benefits of the torsion beam are the low cost and compact design. 

Its obvious flaw is the limited isolation of road undulations. Like it or not, there is still a physical bridge between the left and right side.

There are also limitations in terms of handling, but the modern-day car buyer puts more priority on costs and fuel efficiency. Just like many other automotive technologies, the torsion beam technology has also improved and is sufficient for the average daily driver.

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Arif

Writer

Previously an engineer in an automotive manufacturing company and a highway concessionaire. A part-time research student on biofuels and diesel engines. Obsessed with vehicle electrification and the future of transportation.

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