The Stovebolt Site Forums The Shop Area Engine Shop Wheels, tires, and steering

I grew up around a shop where we bent straight axles as a matter of every day alignment practice, so the idea that a camber problem can't be corrected is a bunch of hogwash. Camber problems cause sidways pull problems and inside/outside tread wear, however, not wandering troubles. If both wheels are approximately the same on the caster measurement, shimming the axle will help. If only one wheel is out, the axle will have to be twisted on one side to bring the caster into specification, not an easy task, but doable with the proper equipment.

One problem most people totally forget, or wish they could, at least, is wheel offset. When a noticeably wider wheel than original is installed, there's only one place for the extra width to go, toward the outside. This moves the tread centerline out, which changes the "scrub radius", the intersection of an imaginary line drawn through the kingpin, and one through the tread centerline. Ideally, these lines should intersect at the road surface to create a good pivot point for steering the wheel. In practice, the lines only do this on a very tall tire/wheel assembly (like the engineers put on the truck when it was new!) Shortening the spindle-to-ground distance with a low-profile tire, and/or a smaller-diameter wheel, plus moving the centerline out creates a great deal of leverage on the spindle, creating- - -you guessed it- - - -steering wander! Increasing the caster will reduce, but not eliminate the problems created by installing those cool-looking, but totally incorrect tires and wheels. The only proper fix would be to re-engineer the axle dimensions to accomodate the shorter, wider wheels by changing the kingpin angle and scrub radius.

Also, be sure the steering gear is exactly on center, and the sector preload is adjusted correctly. There should be absolutely no free play at the center of the steering travel, and the wheels should point straight ahead at that zero-clearance point. Sector gear preload is adjusted with the Pitman arm disconnected, and the turning torque at the steering wheel center nut should increase approximately 10 inch-pounds as the wheel rolls over center. Adjust the sector preload nut on the side of the steering gear opposite the Pitman arm to adjust the preload. Once that adjustment is made, be sure the wheels point straight ahead with the steering gear centered by adjusting tie rod ends.
Jerry