IFS Versus I Beams

Originally most prerunners were built using the Twin I-Beam suspension system originally developed by Ford as far back as the 60’s. Ford’s claim to this design was to give you a car-like ride and still work like a truck.

The design is quite simple; replace the straight axle with two separate suspension beams mounted on either side of the truck, and use radius arms mounted parallel with the truck to locate the beams. All this was suspended by coil-over springs. This new twin i-beam suspension would isolate the two front tires allowing them to move independently keeping more tire on the road.

In the 80’s Ford redesigned the four wheel drive F-150 to use a variation of the i-beam in the form of the Twin-Traction Beam (TTB). In this application, the driver side beam carried a differential and an articulated axleshaft arrangement fed torque to both front wheels. Again the idea here is having the strength of a solid axle and still have both front wheels move independently.

The end of the 90’s saw the first independent four wheel drive system using an a-arm design. This system was used because of its on-road manners. This design also had many in the off-road racing scene up in arms. “How am I going to get more travel?”

Like anything new it only took time before off-road fabricators came up with a way to get more travel out of an a-arm front suspension. Look at Trophy Trucks, they use a short/long arm (SLA) A-arm suspension system and get almost 2 feet of travel. Now most every truck on the road uses a A-arm design except for your heavy duty trucks.

One of the biggest troubles experienced with a modified i-beam or twin-traction beam suspension is the arc the wheel travels when the suspension cycles. Because it is pivoting off of two points that are 90 degrees from each other you get a huge change in camber and caster. This is not as noticeable in the dirt, but it can be scary on the road. You might have seen a “Beamed” truck at a race jump and the tires seem to cup under the truck?

Now even though A-arms do have better on road manners off-road they still perform quite well, as long as you have the right modifications. In order to get more travel out of an A-arm design the arms themselves must be longer. If you have seen a Trophy Truck up close you will notice the attachment points for the arms are only inches apart with the arm length almost the entire width of the truck. This is simply not practical on a daily driven truck.

Most long-travel suspension kits for A-arm vehicles are about 4-6 inches wider per side like the Dixon Bros Racing kit on our Project Desert Ranger. This introduces another trend in A-arm design, long-travel and still being able to retain four wheel drive. Kits are made for Tacomas, Rangers, F-150s and many others.

So let’s look at the pros and cons of each system to help you decide which prerunner suspension works for your new prerunner build.

When you are looking to build a prerunner, and are researching which long travel system is right for your needs, consider these points mentioned, and be sure to ask a lot of questions. The more educated you are about what you are buying the more fun you will have.

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