Inside Ford's I-Beam And Twin-Traction Beam Front End
In 1965, Ford Truck engineering introduced its twin i-beam front suspension on the F-100 pickup. At the time, Ford's marketing campaign claimed the new suspension would "provide a car-like ride, yet still work like a truck." We doubt it's what truck owners were looking for 43 years ago, but whether they knew it or not, America's first long-travel suspension had arrived.
The idea behind the engineering was simple: replace the traditional one-piece solid-beam axle with two separate suspension beams designed to move independently. This new twin i-beam suspension would allow both tires to be isolated from one another and theoretically allow them to stay in better contact with the road. The design sought to maximize durability and simplicity over a conventional A-arm suspension by using long beams that would pivot from the opposite sides of the truck. The long beams meant the tires would see less camber change as the suspension cycled through its range of travel. To locate the beams front to rear, radius arms were mounted in parallel with the truck's frame, and coil springs were used to carry the load.
During World War II, Ford built a larg forging plant in ohio. it was a natural fit to forge the new twin i-beams from steel. The forging process meant that the beams would be extremely strong and compact. To the off-road community, the forged beams translated into robust durability, and it allowed enthusiasts to rework the beams for more suspension travel. modifying the twin i-beams was first done by heating and bending the beams, and then more recently by cutting, rewelding, or even fabricating longer beams all together.
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When Ford launched its redesigned truck line in 1980, the four-wheel-drive F-series trucks also received a twin i-beam suspension. in this application, the driverside beam carried a differential and an articulated axleshaft arrangement fed torque to both front wheels. The forging plant in ohio was scheduled to be shut down, so the new Twin-Traction Beams (TTB) were stamped from steel. The two-wheel-drive forged i-beams were also dropped in favor of a cast i-beam design. The 1980 TTB suspension architecture was similar to the two-wheel-drive truck's twin i-beam design, save for the few tweaks required to pack- age the axles and driveshaft.
With TTB came the first mass-produced independent front suspension four-wheeldrive truck in America. Again, the core truck owners mourned the loss of their solid front axles, but with TTB came the possibility of a long-travel 4x4 front suspension. By modifying the stamped-steel axle beams and adding longer radius arms, the aftermarket suspension builders were able to tune the TTB frontends on Ford trucks for doubledigit wheel travel.