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f-body suspension components
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This is information I've gathered from various sources throughout the web, and from my own experiences. If you have anything to add, or feel that any information on this page is incorrect, please e-mail me so we can talk about it and/or I can correct it. E-mail me at [email protected].
Before I go into too much detail as to which parts are which, and what it is that they do, there's something that must be understood.
First, when the car accelerates and the tires plant, the front center section (nose?) of the differential is being forced upward toward the floorpan of the car as a result of the torque. It's not just the center portion of the rear-end assembly that is torqued in such a manner, but the axle housings (parts that extend from the center portion) are torqued in the same manner as well. There are two components that are on a stock F-body rear end which help to counteract this twisting and forward motion. One is the Lower Control Arms and the other is the Torque Arm.
Lower Control Arms- Lower control arms are one of the most vital components in the rear suspension of a street driven 4th Gen F-body for drag racing. One is attached to the axle housing on each side, and the other end is attached to the floorpan approximately two feet ahead of the axle housing. Being that the LCA is such a short piece, it's major benefit is instantly stopping the rear-end assymbly from torquing forward, in the manner described in the previous paragraph. Stock LCA's are generally of a stamped steel design (thin steel pressed into a "U" shape), and while they're cost effective for GM to produce, they do not do a very good job of keeping that rear-end from torquing. If you click the link at the beginning of this paragraph, you'll see some aftermarket LCA's offered by BMR. If you've ever taken off, tires blazin, and had your rear-end start feeling like it's bouncing, you're stock stamped steel LCA's are more than likely the culprit. As the axle housing twists, flexing that LCA, the LCA acts like a spring, repeatedly flexing and straightening. To get an idea of how the LCA effects the position of the rear axle, hold the middle of a pen between your index finger and thumb, then wiggle one end of the pen with your other hand. That motion is the same as what your axle is trying to do when your axle hops. Obviously, the stronger aftermarket LCA's will not flex like the stock one's will, resulting in the tires having a steady hold on them rather than the flakey upholdings of the stock LCA.
If you need more indepth detail on which is better, tubular or boxed (or solid) LCA's, e-mail me and I'll get back to you as soon as I get around to it.
Torque Arm- Torque arms have a similar function to that of the LCA's. The stock assymbly mounts to the upper and lower portion of the center of the rear-end, and the other end attaches to the tailshaft of the transmission. When the center portion of the rear-end torques upwards, it turns the torque arm into a sort of lever, which pushes up on the tailshaft of the transmission. Once again, the torque arm is made of the same stamped steel design that the LCA's are constructed with, so on such a long suspension piece, it has a LOT of flex in it. If you replace this piece with an aftermarket piece, the twisting of the rear-end will then function to force the tailshaft of the transmission upward, attempting to raise up the midsection of the car. This obviously puts a lot more downward force on the rear-end assymbly, but the amount of downward force will depend on how much torque arm flexes. Torque arm's are made that don't mount to the transmission, but to the floor of the car, which IMO is a MUCH better design, but they're typically a little more expensive. However I feel it's worth the extra money, in that when a torque arm attaching to the transmission will not only put the lifting stress on the transmission, but will put the driveshaft out of alignment (as much as the bushings will flex) with the rear-end, causing severe stress on U-joints. There's a lot more indepth stuff I can go into here, regarding length of torque arm, bushings, and/or height of torque arm mounting position, but you'll have to e-mail me to get that info too. It'd just take too long for me to type it all out like this. If you e-mail me, please be detailed in what you wanna know.
Something else which should be known about aftermarket torque arms, is that some of them offer the ability to adjust pinion angles. Pinion angle is the angle at which the differential sits at while there is no load. For an everyday driver (also, what nonadjustable torque arms are set at), 0� is what is usually recommended. For at the strip, a -2� will provide a little more traction, while not straining the U-joints too much. -4� or more could be used, but then you're starting to put enough of an angle in the drivetrain geometry, that it could take it's toll on your U-joint life.
Panhard Rod- The panhard rod has a pretty simple function. Keeping the differential centered under the car. Replacing this will keep wider tires from rubbing fender wells while taking sharp and/or fast corners. I recommend the adjustable version to everyone. Why mess with getting a solid one? If you're buying it, spend a few extra bucks and get an adjustable one. That way if you ever need to adjust it, you can. Here's a pic of an adjustable panhard rod NOT mounted on the car.
Subframe Connectors- Subframe connectors are very important on our unibody cars. If an f-body spends too much of it's life without subframe connectors, it'll be like the third gen we've all seen that has doors which won't close right. That's from the chassis flexing for soo long, and getting weak over time. This can happen to fourth gens as well. Just don't let it happen to you. ;) Another slight benefit, is that some subframe connectors will reinforce the front mounting point of the LCA's. This is a picture of the BMR subframe connectors, and shows the area's which are reinforced.
LCA Relocation Brackets- These brackets are used to lower the rear mounting point on the control arms. Here's an example of how they function. Find a 20lb dumbbell and pick it up, holding it at your side in the anatomical position. Now, bring the dumbbell up so your arm is in a 90� position. This position will be related to the way the stock LCA mount is. Now, raise your elbow along with the 20lb dumbbell out away from your body. Try to remember how much effort it took for you to do this. Now, straighten your arm back out. This position will be related to the same LCA with the relocation brackets. Try to raise that same 20lb dumbbell away from your body to the side now. Notice how much more difficult that was? The object of relocation brackets is to hold that axle housing in place moreso than the stock mounting location would allow (on a stock height vehicle). On a lowered vehicle, these relocation brackets simply function in putting the LCA angle back to the angle it was before the vehicle was lowered, gaining back the traction that was lost when the vehicle was lowered.
Bushings- Bushings are really what determine just how "streetable" certain suspension components are. They are what usually absorbs the shock of sudden impact throughout your suspension. For those of you who either don't know what a bushing is, or don't know where it goes, look at this picture. You see the red "things" on each end of the LCA's? Those are bushings. A bolt goes through the middle of those bushings, which is basically what connects the suspension to the body of the car. If you have a bushing that doesn't have much "give" in it, then that results in a hard ride, but very responsive car.
There are four types of bushings. Rubber, Polyeurothane, Spherical rod ends, and Del-a-lum. Rubber is by far the most forgiving. It absorbs the most shock out of all the different types of bushings, but it also is about the worst performing. The ability of it to absorb the shock also makes it give more when you make a fast turn, or hit the throttle quickly, resulting in a slower response. Polyeurothane is probably the most often used in aftermarket suspension pieces. It's a much harder (more responsive) material that doesn't wear out. The only downside to these is a little rougher ride, and the need to grease them to keep them from squeaking. Sherical rod ends are the third type of bushing typically used. They feature a single eyelet that the mounting bolt goes through. There is virtually NO give with these, and the ride is fairly harsh. The benefits are that it is definitely the most responsive type of "bushing", and it still allows for something called bind. I'm not going indepth on what bind is right now though. That's more for roadracing fanatics, and this write-up is a little more drag racing oriented. Del-a-lum is the final type of bushing offered. These are pretty much specifically offered from Global West (I believe). I haven't read too much about these, but apparently they give the responsiveness of poly, with the gentle ride of the rubber bushings. You CAN mix and match these bushings on a suspension piece to get your suspension right where you're comfortable with it. For instance, if you don't want the harsher ride of the polyeurothane bushings, you can put a poly bushing on one end, and a rubber bushing on the other. While the poly end won't 'give' very much, the rubber bushing will 'give' as much as it's density allows it to, providing a softer ride than the poly/poly combo, but more firm than a rubber/rubber combo.
Hal Shocks- HAL is one of the few aftermarket companies which offer a multi-level adjustable shock for the F-body. The HAL's feature 12-way adjustability, and are of a coil-over design. For simplicities sake, picture a coil-over as having the spring attach at the stock top mounting location, and the bottom spring mount attaches at variable points on the shock. Something that you have to understand about shocks, is they extend (we'll call it bound) and compress (we'll call this rebound). The beautiful thing about the HAL shock's adjustability, is that they allow you to adjust how quickly the shock will bound and rebound. The lower settings allow a VERY quick suspension travel, and give very quick weight transfer. The draw back to this, is that it also provides VERY loose handling, which can be dangerous on the street.
Tuning the HAL's- What settings you use on your HAL shocks is going to vary greatly depending on the power of your car, as well as how much traction your tires can provide. For starters, on most (street/strip) cars you're going to want to start with the front shocks at the "1" setting. This will allow the front end of the car to raise VERY quickly when you hit the go pedal. This is a good thing, so long as you're not pulling some hellacious wheel stands. The rear shocks are where you may have to do a lot more tuning. The settings for your rear shocks are directly related to just how much traction you can get your tires to provide. Just so we have a constant here, we'll say that you're running ET Street drag radials. For starters, set the rear shocks on the "2" setting. If you can video tape your launch when you do this, you'll notice that the back end of the car drops, and the front end rises. For the explanations sake, we'll say there was NO tire spin, but you did notice that the right rear dipped a little more than the left rear did when the car launched. This angled launch relies more on one rear tire than the other for traction. To compensate for this, turn the right rear shock to a stiffer setting than that of the left rear. The stiffer setting in that shock will prevent it from dipping as fast, and will help to keep the car level. Make another pass, and notice that the car still dead hooks but stays more level, while the rear-end still dips down quite a bit. The rear end dipping like this is actually hurting your 60' time. The theory in this, is that torsional energy of the car launching is wasting energy dropping the rear end, rather than rotating the tires thus launching the car forward. Keep in mind though, having the rear suspension drop like that gives more weight transfer which helps the tires hook up. So of course the stickier tires you have, the less weight transfer it requires to get traction. You want to make the rear suspension as firm as you can, until your tires will no longer keep traction. Once you do this, you may not give the impressive wheel stands anymore (unless you've got crazy power), but I guarantee you you're 60' times will improve.
If anything in here isn't worded very well, or is confusing, drop me a line and I'll try and reword it.
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