Equal Length Tie Rod system

The Ford twin I beam front end was introduced in 1965 on Ford 2wd trucks. The basic design remained unchanged until 1979. One of the most unusual features of the Ford 2wd truck is Rear steer. That means the steering and linkage is behind the front axle centerline. Ford used rear steer on many passenger cars as well. Ford produced many fast successful cars with rear steer. Early Mustangs, Fairlane, and Torinos are good examples.  I think this was their reasoning back in the day for better steering geometry. The idea is this: Picture the front suspension looking down from the top. Draw an imaginary line from the center of the steering axis through the center of the tie rod hole and project it until the 2 lines left and right intersect in the rear. That is the center of the rear axle. This is how Ford decided where the steering arms needed to be. Also this is the primary reason you do not want to turn a rear steering spindle around when converting to a front steer. I have seen many done that way too, back when these trucks were the class 8 choice. I may cover that topic at a later date.

    Why Ford did not try to create an equal length tie rod system remains a mystery. My guess is that it was considered,  but economics dictated a Y style system. Obviously less complicated and cheaper to build regardless of the toe change problems. This is one of the reasons Ford trucks has a reputation of cupping front tires. You have a beam making a constant camber change and a Y style steering with toe change. When you really stop and think about it , This front end should not have worked at all! But time has proven otherwise. You really do not notice this driving a Ford and the changes that occur are within  tolerable limits. Off road racing dictates a different steering system. There were just too many problems with steering tie rods bending from hard off road use. The position of the Ford steering gear box is pretty close to the inside beam pivot. By creating an idler arm to swing from the opposite beam pivot we accomplish our left side tie rod starting point. The primary complication to overcome is driving the idler. The simple method is creating a special pitman arm.  The tie rod to the right wheel and the link to drive the idler arm both come off the pitman arm now. This all sounds easy enough until you start trying for some serious wheel travel. The tie rods have to go through the radius arm and there is only so much room to work with. Also we have to avoid the tie rods colliding with each other as well. The system we designed for the spare parts truck cycles correctly through up to 26 inches of wheel travel. We have almost totally eliminated the bump steer as a result. Here are some pictures of our system.

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Last modified: March 19, 2009