I-Beam vs A-Arm: Which One is Actually Best?

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So you’ve just scored a Ford Ranger and already decided you want to turn it into a prerunner. However, after doing some research you’ve found out that there a few different options when it comes to a long travel setup.

You could either go with an I-beam setup, or you could spend the extra money and go with an A-arm setup. Which is better is really going to depend on what you plan on using the truck for.

Quick History Lesson

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Ford originally designed the I-beam suspension setup back in the 60s. It was an attempt at giving their trucks a better ride quality without sacrificing the workhorse nature of a pickup truck.

The design was pretty simple, instead of using a straight axle, they used two beams, each connected to opposite sides of the frame. All of which was on coil-over style springs. This design allowed the front wheels to move independently of each other, and thus gave a much better ride.

In the 80s Ford took the I-beam design and integrated it with a 4WD system. The resulting product was known as Twin-Traction Beam (TTB). It worked by putting a differential in the driver side suspension beam, and “articulated” axle-shafts to connect the wheels to the differential. Not only was this design very strong, it also provided lots of travel and good ride quality.

Alignment Throughout Suspension Cycle

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One of the biggest issues with the twin I-beam design is how the alignment is changed throughout the suspension cycle. You may have noticed how the tires have a massive amount of positive camber when the suspension is drooped out.

The tires will also gain a massive amount of negative camber when the suspension is compressed to its maximum. Not only is there massive camber change throughout the suspension cycle there is also toe change and caster change. None of this is noticeable on the dirt where traction is severely limited. But, on the street, this can cause extremely unsafe handling.

The independent front suspension design doesn’t have this issue. Toe, camber, and caster are relatively static throughout the suspension cycle. This allows for much safer on-road handling characteristics, hence why Ford stopped using the I-beam/TTB design.

Suspension Strength

Obviously one of the most important things for desert race trucks is the strength. Prerunning/racing will put every suspension and chassis component under extreme stress. This is why most “trophy” trucks are 2WD because most 4WD systems simply cannot withstand the stress.

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Although modern IFS suspension designs are extremely strong they still have more mounting points and more points where the suspension is pivoting. The I-beam design only uses 2 chassis mounting point, whereas the IFS design typically uses four chassis mounting points. For this reason, the IFS design is inherently weaker than the I-beam design, but only marginally so. This is especially true when you are on a strict budget and can afford all the nicest parts for your suspension setup.

Cost

This is probably the most important factor in this article. If money wasn’t an object for your truck build, chances are that you wouldn’t be reading this article. Due to the complexity of most IFS suspension setups, an I-beam suspension setup is almost always vastly cheaper. Not only is the entire design simpler, but the parts don’t have to be built out of super high-end materials.

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A lot of the cost factor is arguable based on if you can fabricate yourself or not. If you’re able to design and fabricate your entire setup by yourself the price difference could possibly be negligible. However, most of us can’t design and build the entire setup by ourselves especially since the IFS design is more complicated.

What The Pros Have to Say

I’ve personally never had a long travel truck since Jeeps are really my thing. So, I talked to my friend Kacy Clark, founder and owner of American Motorsports to see what he had to say.

“If you’re building from scratch an a-arm setup is well worth it, and really no more expensive than an I-beam setup,” Clark said. “If trying to fit a factory setup, an I-beam vehicle is cheaper / less work to keep I-beam suspension. Both give great travel, however A-arm has much better geometry throughout its suspension cycle compared to I-beam.”

Some race teams use I-beam suspension to help mimic the suspension travel of the race truck.

I-beam suspension is a great way to get a lot of travel without moving the motor back and suspension points forward as compared to stock. Most quality A-arm builds would require the motor to be moved back, bringing the bulkhead forward.

“Once you get the motor out of the way you can bring the suspension mounting points as close to center as possible,” Clark continued. “The closer the A-arm mounting points are together, the longer the arms you can run.”

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“I would always prefer an A-arm setup,” Clark said. “Less weight, proper geometry, and better performance. However, a great built I-beam suspension can still be a great setup. Although, you don’t see any new vehicles being built with I-beams for a reason unless it’s a ‘new’ build on an older chassis.”

Price really depends on the builder’s ability to do the work himself. Both require a bit of work, but A-arm kits are more readily available. However, most a-arm kits could be considered mid travel. I-beam kits are usually a little more, but give more travel than a mid travel a-arm kit.

Summary

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No matter how you dice it, the I-beam setup is always going to be significantly cheaper. But, it comes at the cost of poor on-road handling. If you’re okay with awful on-road handling than an I-beam setup makes sense. On the contrary, most of us drive our off-road toys on the street almost every day.

Although your truck isn’t a sports car, it likely handles well for what it is because of its IFS setup. If you want the best of both worlds an A-arm setup is the only way to go, but be prepared to shell out a hefty amount of cash.

About the author

Bryce Cleveland

Bryce has been in the automotive industry for most of his life. He’s done everything from fixing cars, flipping cars, writing about cars, and everything in-between. He has owned a total of 18 vehicles, most of which he owned before the age of 20. He currently drives his 2015 Ford Fiesta ST every single day and has plans to buy his third Jeep XJ Cherokee very soon.
Read My Articles

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