Here's a Suspension Glossary as it pertains to WJs.
understanding "how suspension works" is far beyond what can be conveyed with a single forum thread. I'd suggest going to "How Stuff Works dot com" and looking up suspension. There are many books written on suspension design. Get in there and start playing with things and see how they relate.
- are responsible for "controlling" and locating an axle or knuckle as it moves through its travel. In our case, the control arms are where caster can be adjusted (with aftermarket arms) and also responsible for maintaining the proper driveshaft angle. On an even greater scale, the control arms are what are responsible for the position of the wheels in the wheel wells as the axle moves up and down. The lengths and angles of the control arms also affects handling, braking, and acceleration with how body roll, squat, and anti-squat are handled (but that's on the advanced side of suspension considerations).
On the WJ, there are 2 upper and 2 lower control arms on the front axle, and a single upper control arm (see "A-arm") and 2 lower control arms on the rear axle
- a control arm that mounts in two places on the body/frame and a single place on the axle. Also called a "wishbone" on some types of suspension. The WJ uses a large A-arm at the top of the rear axle to act as both the control arm and as the track bar - it controls the arc of motion up/down and also positions the axle side-to-side. There is a single ball joint at the axle side and two rubber bushings at the body side.
- A track bar is responsible for positioning the axle side-to-side. It is referred to in some applications as a panhard bar or panhard rod. As the axle moves up and down, the track bar will force the axle to move side-to-side slightly. In general, the movement of the axle up and down eventually creates binding between the arc that the control arms force the axle to travel and the arc that the track bar forces the axle to travel. The track bar should (in general) be parallel to the drag link to prevent "bump steer". The WJ has only a single track bar (on the front axle) but most solid-axle Jeeps have a track bar both front and rear.
Knuckle (or spindle)
- this is the housing at the ends of the axle where the brakes, wheel bearing, and hubs mount. They are connected to the main axle housing by two ball joints (see below) which let the knuckle turn. The rear axle on our Jeeps does not have a knuckle but the front.
- The hub is the portion of the knuckle where the wheel and brake rotor attach. It is supported by the unit bearing and to a lesser extent, the axle shaft. The wheel studs are pressed into the hub, pass through the brake rotor, and then through the wheel.
- This is a fancy term for wheel bearing. It is a large, sealed double-tapered bearing assembly that is directly responsible for supporting the entire weight of the vehicle PLUS any cornering or impact forces. They are considered a wear item. Wear can be accelerated by off-road driving, abuse, wheel spacers, and lower-backspace wheels.
- a type of flex joint that only allows motion on one axis - twisting. This allows the knuckle to rotate in place as you steer it. THere are two ball joints on each side of the front axle.
- also called "anti-roll bars" and "anti-sway bars". It has nothing to do with trailer sway, that's a different issue. Sway bars are a torsion spring that links one side of the axle to the other. They reduce body roll (aka "roll stiffness") on that particular axle and can affect how the other axle "feels". For instance - a stiffer rear sway bar reduces roll at the rear of the vehicle but in turn makes the steering seem more responsive. A sway bar works as follows: as you travel around a corner, one side of the suspension compresses and the other droops. The sway bar twists, transferring more force from the drooping wheel to the compressing wheel and helping level the vehicle as well as providing more grip at the compressing wheel. Sway bars can also limit the overall amount of travel available if they are tuned too stiff for the application. They also cause both sides of the axle to be more affected by a bump in the road. Many Jeepers disconnect their sway bars off-road to improve wheel travel and ride comfort. There are both stiffer sway bars and weaker sway bars available - to improve street and trail performance, respectively. With sway bars, what works great on the street works poorly for the trail.
Sway bar end links
- connects the sway bar to the axle (front) or to the frame (rear). These are often replaced with "quick disconnects" that make it easier to disconnect the sway bar(s) for off-road driving.
- Duh, springs! Springs are directly responsible for providing roll stiffness and supporting the axle in a position away from the vehicle. The stiffer the spring, the less the body will roll under cornering, the less it will squat and dive under acceleration and braking, and the less it will compress with a heavy load. The stiffer the spring, the harsher the ride (in general).
- Shocks are energy absorbers that absorb energy differently in each direction. They tend to heavily damp the upward forces while being more free-moving in the downward direction - this allows for better weight transfer during cornering. The shocks are directly responsible for the ride comfort in the vehicle and also keeping the body motions controlled (and thus, the force applied to the tires much more constant). Weak shocks can reduce traction at the tire as the suspension cycles up and down and force is transferred off the tire (briefly). A secondary effect of all shock absorbers is that they apply some additional roll stiffness by reducing the rate at which the body roll occurs - but not affecting the total amount of body roll you will experience in steady-state cornering (like on a skid pad).
- these are found between the spring and the body and between the spring and the axle. They are metal-reinforced rubber discs that reduce the amount of vibration and noise that are transmitted from the road to the cabin. As they compress over time, they can be responsible for lost ride height (sag).
- these are foam-rubber bumpers between the axle and the body. They prevent the axle from travelling too far upward on large bumps or when flexing off-road. This is necessary because it will both keep the tires from stuffing up into the fenders and chewing up the sheet metal AND will keep the shocks from hitting the bottom of their travel (bottoming out) and permanently damaging the shocks.
- a simple lift consisting of polyurethane (or sometimes metal) spacers. These are placed between the axle and spring or between the body and the spring to get a modest lift for little investment. These are usually 1.75" to 2.5" in length, some as high as 3" (although there is much more needed at 3" lift, so why bother with spacers?)
Adjustable Track Bar
As with a standard track bar, this provides lateral support for the axle as it travels up and down. As the WJ is lifted, the axle shifts to the driver's side. The adjustable track bar allows you to re-center the axle.
Also called "Quicker Disconnects" (by JKS), these allow the front sway bar to be quickly disconnected from the front axle without using any tools.
Adjustable Control Arms
- These arms are adjustable in length, allowing the user to fine-tune the caster, driveline angle, and re-center the wheel in the wheel well.
- These are pivot points - usually at the ends of control arms - that replace rubber bushings and allow the arm to pivot more freely. "Johnny Joint" is a common brand of flex joint made by Currie.
- These are replacement long arms that use a new mounting point either bolted or welded to the frame. The longer arm allows flatter control arm angles for a smoother ride and more available wheel travel.
- this connects the steering gear (or steering box) to the front axle knuckles. It is what controls the steering angle of the passenger side wheel by means of input from the pitman arm. The drag link is adjustable, this adjustment is part of centering the steering wheel.
- this connects the passenger side knuckle to the driver's side knuckle (at least on the WJ). On many Jeeps, the tie rod doesn't attach to the passenger side knuckle at all, but rather to mid-way in the drag link in the "inverted y" steering arrangement. The tie rod is adjustable, this adjustment is for setting the total toe figure during vehicle alignment.
Tie Rod End
- a form of flexible joint found in the steering system. It allows the joint to pivot on 3 axes - it can move on 2 axes like a joystick and also can rotate in place. These are common wear items that cause issues with imprecise steering and even the dreaded Death Wobble. There are two tie rod ends on the drag link and two on the tie rod.
- this connects between the axle housing and either the drag link or the tie rod (depending on your setup). It is a 50/50 damper. Basically, a shock absorber that absorbs energy equally in both directions (unlike your actual shocks). This will absorb most of the energy from hitting a bumper or a pothole. It also helps reduce resonant effects in the steering system and keeps tiny bumps from magnifying into Death Wobble.
- this is a torque arm that comes out of the steering gear (steering box). It has a large spline on one end and a tapered hole on the other end. This is what converts the rotational motion inside the steering gear into an actual linear motion. The tapered hole connects to the drag link by means of a tie rod end.
- the process by why the steering angle changes as the axle travels up and down. This is NOT the same as hitting and pothole and feeling the steering wheel jerk.
- the process where the front axle of the Jeep moves uncontrollably from side-to-side. This is a form of resonance in the steering system/axle that can be caused by many different factors - including but not limited to - excessive tire pressure, tire wear, tire damage, worn tie rod ends, worn drag link ends, torn track bar bushings, improper alignment, worn ball joints. Death Wobble is very unsettling and usually occurs at higher speeds (45mph+) and cannot be stopped until the Jeep slows down nearly to a stop. Here is an example of Death Wobble: