It doesn’t much matter how strong or geometrically correct a steering system is if it’s not used properly. A driver who tends to run into large and immovable objects blindly should consider a linkage mounted higher, such as Tri-County Gear&8217s. Better yet, a setup with the linkage behind the front axle could be well protected. Many Hi-Lift handles have become tie-rod repair material because of goofs like this. |
This simple and nearly factory steering setup is quite good in that the steering box is braced with a Currie support and the drag link sits in a slight downward angle from the box to the steering arm. The linkage is also reasonably well protected from trail hazards, being above the springs, and it is straight. A closer look, however, reveals that the tie rod is lengthened by using an early Jeep tie-rod end, which has a bend in it (far left), and the smallish tie rod is lengthened with a welded-in piece (center). Both are weak links in this steering chain. Usually, a drop pitman arm isnt the best solution for drag-link angles, because they put extra stress on the steering box, which in turn does the same to the frame. |
In the early days of four-wheeling, people experimented a bit, as is evidenced by this FWD. Having the drag link slope upward at normal ride height is no longer considered ideal, and neither is running solid tires. Notice also the somewhat primitive tie-rod ends. |
Steering is nothing to play with, but this toy's steering serves to show the basics of steering. A shaft connected to the steering wheel transfers rotational motion into a device, which creates side-to-side movement. On bigger Jeeps, the bent rod and loop would be the steering box (the drag link is eliminated in this setup). This movement is again turned into rotational force through a tie rod connected to steering arms at each wheel. The yellow plastic bushings act as knuckles, on which the steering turns. Even on this little toy Jeep, things such as kingpin inclination, camber, caster, and Ackermann angles must be taken into account, or this would be a nearly undriveable toy. |
Caster angle is the degree the kingpin axis leans forward (negative) or backward (positive) and highly affects the self-centering properties of the steering. Too little and the vehicle is very hard to drive straight; too much and the steering gets hard, plus the front tires do a road-grader imitation at full lock. Good axle builders machine and/or weld the spring pads to place the knuckles at the correct angle for the application. |
Steering should take precedence over U-joint angles, but in cases where both caster and driveshaft angles can&8217t be made to work, the knuckles can be rotated relative to the diff housing, effectively raising the pinion while still maintaining the steering geometry. Here a Dynatrac axle is checked carefully for correct caster. |
This illustration shows that the pivot points in the knuckles aren't vertical, as seen from the side, and how that creates caster (left). To the right, although exaggerated, this frontal view of an axle can be studied for a while. It shows how wider wheels affect front-end geometry by putting the center of the tire outboard of the steering axis (kingpin) inclination and that knuckles aren't turning around a vertical plane, seen from the front, either. These, and other angles, are all there and of a specific value for a reason--namely, to make a vehicle steer and handle correctly. If you noticed that taller tires would offset the use of wider wheels (as far as the kingpin inclination is concerned), you're getting the hang of it. |
Other ways to influence caster include using wedges between the spring pads and spring or using nonstock-length shackles. Wedges can work loose or break but are good for experimenting before building the axle. Shackles can seldom be shorter than stock and still accommodate full suspension travel, but they will increase caster on a front-shackle application. More common are longer shackles, which lessen the caster and often contribute to instability in general. Hopefully, it doesn’t get any worse than this butchered C shackle with a butt-welded extension that&8217s just waiting to break. |
One way to make the steering linkage better protected and lessen the drag-link angle is to put the tie-rod ends on top of the factory steering arms. After the original taper is machined out, a sleeve--which has the taper opening up rather than down--is pressed in. This modification doesn&8217t alter anything in the steering geometry other than the drag-link angle and nets a 2.5- to 3-inch higher (depending on tie-rod-end size) tie-rod position. |
Bumpsteer is when the suspension moves and the wheels turn side to side as a result. Too much height difference between the pitman and steering arm, such as after a tall lift or spring-over conversion, puts the drag link at an angle that creates bumpsteer. Some people believe that a bend or two cures that. It doesn’t. While the bends may help avoid tie-rod-end bind, they do nothing for the steering geometry. Worse is that a bent link is a weak link, and steering linkage is not a good place to have anything weak. A steering setup that needs bent links to work could use some reengineering, even if it doesn&8217t look quite this bad. |
Often overlooked, the Ackermann angle is largely responsible for tight turning. In theory, a line from the tie-rod end on the steering arm through the imaginary line of the kingpin axis should hit the center of the rear axle. In other words, shorter-wheelbase vehicles should have the steering arm at a more pronounced angle (closer to the wheel) than would a longer chassis. Shown is a knuckle with both a stock steering arm (left) and a custom, rear-facing arm. Notice both steering arms are at an angle (i.e. the Ackermann angle) to the spindle-mounting surface. |
Swapping in knuckles (or complete axles) from other vehicles can change steering properties drastically. Even if the caster and camber happen to be correct, chances are the Ackermann angle won’t be. While it certainly can&8217t hurt to have perfect steering geometry, as long as there is some Ackermann angle (in the right direction), it may not be crucial. This photo shows an early Blazer knuckle (left), which despite its longer wheelbase, has more of an angle than the Jeep CJ knuckle on the right. Then again, early Jeep CJs were way off and could be made to handle far better with more Ackermann than stock. |
A steering system is made up from many parts, each with its own demands. One of the primary parts in the chain is the steering shaft, which generally has at least one U-joint between the column and box. Borgeson, maker of heavy-duty steering shafts, points out that the U-joint angle shouldn’t exceed 30 degrees (pictured). Also, Borgeson recommends a support bearing on shafts with more than two U-joints and on really long two-joint shafts. Additionally, do not weld on the U-joints, warns Borgeson, because that can cook the grease out of the joint and fry the seals. |
If the brakes fail, fix the horn, but where would you be without steering? Being able to steer is usually the most important virtue of a vehicle, so the steering is not the place to have any discrepancies. Books have been written on the subject of steering because it is so important and complex, and in these few pages, we'll hit on some of the dos and don'ts. Even factory steering geometry is not always perfect, but that's no reason to make it worse.
BENT ON GOING STRAIGHT
Common sense goes a long way when modifying or just trying to understand things, and a steering system is no exception. For example, a drag link, one of the simplest parts in the system, is often quite misunderstood. Its purpose is to connect the pitman arm (on the steering box) with the rest of the steering linkage. Still, although everybody knows the shortest path between two points is a straight line, logic often disappears when it comes to drag links.
Sometimes, even magazine features and suspension manufacturers claim a more or less S-shaped drag link restores steering geometry. Well, it's not quite that easy.
No matter what shape the drag link is, it's still only where its ends are that counts. If you lift a vehicle, the drag link generally gets a steeper angle, because the pitman arm is now that much higher than the steering arm. That tends to lead to bumpsteer. Bend that drag link any way you want. It won't change the height difference between the ends. Bends, however, are built-in weak spots. Raise the steering arms or lower the box, but do not automatically think that bending a drag link will make the steering geometry any better.
Sometimes you'll see gussets on (purposely) bent drag links installed in an effort to strengthen the bend-induced weak spot. Unfortunately, unless done correctly, the gusset work can create two weak spots out of the one bend, making a bad part worse. So, whenever possible, build your steering with a straight drag link. It may be more work, but it'll be worth it.
TWO WRONGS DON'T MAKE A RIGHT
A Panhard rod is affected much the same as a drag link when vehicle ride height is altered. The Panhard rod's purpose is to locate the axle side to side and is normally not used on leaf-sprung vehicles, where the springs do that job too. If the Panhard rod is parallel to the drag link, there is indeed no bumpsteer in the normal sense, but just like a drag link, the Panhard rod should be kept as close to horizontal as possible for things to work right. With too much slope on the Panhard rod, the entire axle will move sideways as the suspension cycles. Should the Panhard rod be at a steep angle and not parallel to the drag link, not only will the axle move sideways, but the tires will also steer based on suspension movement. That could be a little much, even on a trail-only vehicle. Luckily, it's easy to drop the frame mount or raise the axle end of a Panhard rod.
SHOW VERSUS GO
There's a huge difference between the demands put on a show vehicle and what a trail rig or daily driver needs to be able to accomplish safely. Please leave the bent steering links to the fairground-only crowd as well as any chromed steering components. Steering systems are not impervious to hydrogen embrittlement, so don't weaken important parts on purpose.
That something looks great on a show vehicle doesn't mean it's functional for heavy-duty use. If you want to copy something, look instead at the most trail-abused vehicle around--if its hardware and steering solutions seem to last through repeated trail use, it's probably a good setup. However, also quiz the driver about the handling qualities, because many trail rigs are a handful and a half on the road.
GOING ALL THE WAY
While the steering system largely is a simple combination of levers and pivot points, we should still pay attention to the physics of those levers. Swapping pitman arms, for example, is relatively common, but that a pitman arm fits the splines and clears things around the box as desired doesn't mean it's the right one. There is a relationship between the length of the pitman arm and steering arms that must be maintained to keep the steering working at full efficiency. A pitman arm that's too short won't allow full steering. Also, it's better to have the steering stops on the axle (or even the tires) to limit the steering than to allow the box to act as a stop. That way, when a tire hits an obstacle, the forces aren't fed back into a maxed-out steering box then the frame.
A pitman arm that's too long creates unnecessarily hard steering and is harder on the box. The simple solution is to use a pitman arm that's slightly longer than the effective length of the steering arms. An alternative is to change to internal stops in the box.
THINK STRAIGHT
There's always a weak link in every setup, including steering, and if we had a choice, we'd pick the tie rod as a fuse. Our simple reasoning is that it's the one steering component that's the easiest to do without (yes, with correct steering geometry you can drive with just one steered wheel, sort of). The tie rod is also the easiest to fix or make a reasonable facsimile of. Hopefully, nothing in your steering will ever break or bend, but if it does, at least make sure it's something that's relatively simple to repair on the spot.
With a little common sense, a basic understanding of geometry, and keen observational skills, safe steering solutions do exist. FW