Ford’s Twin I-Beam Front Suspension Was A Simple But Genius Design

For the first few decades of the 20th century, pickup trucks were pretty primitive machines. Spartan cabs with little in the way of creature comforts, simple, torquey drivetrains, and solid axle front suspensions were the name of the game. After World War II, however, trucks started to get small luxuries like headliners, synchronized transmissions, and chrome trim as hand-me-downs from their more civilized coupe, sedan, and wagon cousins. Their underpinnings remained positively agricultural, however, until General Motors revolutionized truck suspension with the all-new front double wishbone setup for half-ton pickups.

See, up until then, the state of the art in pickup truck front suspension was the tried and true solid axle. It was basically a small I-beam with a wheel on each end suspended by, depending on the manufacturer and era, some combination of leaf springs, torsion rods, and shock absorbers. GM’s double wishbone setup used a pair of wishbone shaped assemblies sprung by individual coil springs to isolate the front wheels from one another. This was far from a new technology, but it was new to trucks.

Meanwhile, in Dearborn, the big brains at the Ford Motor Company were busy at work on their own independent suspension design. Ford engineers started tinkering with an IFS for the company’s F-series trucks in 1959, and GM’s introduction of its double wishbone setup kicked the boys at Ford into overdrive. Finally, in 1965, Ford announced the twin I-beam front suspension — a technology that the company would use for the next five decades.

Ford’s twin I-beam design was as simple as it was brilliant. Basically, it consisted of two short, heavy duty, I-beam axles made of forged chromoly. The beams were offset and overlapping, hung from either side of a transverse frame rail under the truck’s front end. The attachment points were pivots, and they were connected at the opposite side of the truck from the wheel they carried — the right wheel pivot was on the left side of the truck and vice-versa. Each axle had a coil spring, a shock absorber, and a heavy steel radius arm to keep it from moving fore and aft. This suspension setup was a huge step up in handling and ride quality for Ford, and soon it was slapped on everything from the F-100 to the F-350.

While it was largely a revelation, the twin I-beam setup did have its drawbacks. Since it worked like an old-time swing axle, the front wheels’ camber changed whenever the axle moved up and down. This wasn’t as marked as the camber change on, say, a Corvair or Volkswagen Beetle, but it was still there and led to uneven tire wear and slightly unpredictable handling on paved roads. In addition, it can be tricky to align the wheels on a twin I-beam setup, especially as the suspension parts wear.

Aside from those issues, the twin I-beam suspension setup was a big success for Ford. The company kept improving on the design over the years — replacing the old-school kingpin steering knuckles with modern ball joints, for example, and introducing a 4WD version in 1980 called the Twin Traction Beam — but eventually Ford replaced the twin I-beam on the F-150 with the lighter, more modern A-arm suspension.