In my last article, we went through the basics of the front sway bar and how it affects your car when the suspension takes a set in hard cornering. We’re going to tie that into the rear suspension in this article. In the previous article, I told you that the main purpose of a sway bar is to keep the body/chassis from leaning during hard cornering.
This is true. However, there’s more to it. This is especially true when you’ve got a rear sway bar that is engineered to work properly with your current suspension setup. Remember, bigger isn’t always better. Too much sway bar and you can end up destroying all the money and hard work you put into building that competition suspension underpinning your car
Besides Controlling Body Lean, What Do Sway bars Do?
When you work with a suspension professional to properly engineer your whole suspension system, a good sway bar setup, front, and rear, does so much more than just controlling body lean. It can also control what we call “wheel hop” in corners. This is when the hard cornering causes the inside wheel(s) to lift to the point they begin to lose contact with the track or road surface.
There’s a whole science behind this, and it gets pretty technical, but I’m going to keep this easy to understand. If you want to understand the science better, there’s a good discussion of it on Reddit. Put simply, a well-engineered sway bar setup will help transfer laterally. So when the car enters a corner, the wheels that are losing traction, the inside wheels, are given more traction by the wheel on the opposite side and the opposite end of the car.
For an excellent example of this, watch a road course race, especially a NASCAR road course race. The car enters the corner, causing the weight of the car to transfer to the outside wheels. When this happens, the centripetal force is trying to lift the inside wheels. The torsional (twisting) action against the sway bar, plants the wheels inside the corner, laterally transferring traction through the frame.
Again, too much bar and that lateral transfer of traction defeat itself, so you want a neutral balance. If your car experiences understeer, where you have to keep adding steering wheel input to go around a corner at speed, a bigger rear sway bar will force more traction into the front wheels and counteract the understeer.
The reverse is true for oversteer, which is where the rear of the car wants to come around under hard cornering loads. A bigger front bar and/or smaller rear bar corrects this oversteer condition. The action of lateral traction transfer also illustrates why a good set of subframe connectors is so important in a unibody car. Now let’s get to installing a rear sway bar on your GM strip burner.
Tools and Materials You’ll Need
If you’ve got them, ramps are great for this project. If not, a jack and two jack stands are required. You’ll also need two blocks of wood for one of the front tires. What I’ve done for an added measure of safety is screwed two six-inch long sections of a 4X4 to a piece of plywood. I then jack one front wheel up and slide this under that wheel and lower the wheel between the two blocks. The rest of the stuff you’ll need is as follows:
• Wrench set
• Socket set and ratchet
• Drill and drill bit set
• Vise or large slip joint pliers for the bushings
• New sway bar kit
Step 1: Raise the Rear!
Lift the rear of the car with the jack under the rear end housing. Remember, it’s got to be high enough for you to slide under and work somewhat comfortably. There’s also the good chance that you’ll need to contort yourself a bit to reach the end links, so keep that in mind. Slide the jack stands under the frame well in front of rear wheels and carefully lower the car onto the stands. Remove the jack.
Step 2: Prep the Sway Bar for Installation
Open the small grease “squeezers” and squeeze a little grease on the inside of the axle bracket bushings. Slide these over the sway bar and rotate them a few times to evenly distribute the grease. If your sway bar kit requires you to install bushings for the end links, like this kit from Hellwig. Grease the bushings up and press them into the end links with either a vise or a large pair of slip joint pliers.
Step 3: Remove the Old Sway Bar
If your car doesn’t already have a sway bar installed, skip ahead to Step 3. The rear sway bar connects to the car in four places. Two of these are the same no matter what year car or suspension type you’ve got: either side of the differential housing.
The other two will depend on what year the car is and what type of suspension you’ve got. On cars with solid axles, the ends of the sway bar will connect to the rear cross member via end links and end link brackets. On cars independent rear suspensions, they’ll connect to the end links that are bolted to the control arms.
Other than where the end links are, removing the old sway bar is pretty much the same across the board. Loosen and remove the end links. Next, loosen and remove the axle housing shackles. Finally, pull the sway bar out. Some designs may make you twist and wiggle the bar to get it out, while with others, it’ll just drop out after being disconnected.
Step 4: Connect the Axle Housing/Frame Mount Brackets
Jimmy, wiggle, twist, or simply lift the new rear sway bar into position. Loosely clamp the sway bar to the axle housing brackets. Tighten the nuts enough that the sway bar doesn’t flop around, but leave it loose enough that you can maneuver it from side to side and move the end links up and down with ease. For good looks, measure from the inside of the tire to the bracket on each side and set these measurements to be identical. It just looks more professional this way.
If you’ve got a newer car equipped with an independent rear end, you’ll be loosely attaching the rear sway bar frame mounts, not the axle housing brackets. Sway bars on these cars don’t attach to the differential at all.
Step 5: Connect the End Links
As I mentioned before, some sway bars are adjustable. This adjustability comes in two forms: the end links are adjustable for length/height to reach the point on the frame/control arm that they attach to and the sway bar, and for the perceived stiffness of the bar itself. This second type of adjustability comes in the form of multiple holes in the ends of the bars where they connect to the end links. My recommendation is that you use the middle hole to start off with.
On older cars, you’re most likely going to need to attach the end links to the sway bar ends and then attach the end link frame brackets to the end links. Once that’s accomplished, you’ll need to rotate the end links into position on the cross member and mark when the brackets come into contact with the frame.
Disconnect the brackets from the end links and mark the hole in the center of the bracket on the cross member. Using a half-inch drill bit, drill a hole in the center of the cross member for each bracket, then attach the bracket to the cross member with the included hardware. Tighten everything up.
Step 6: Lower, Test Drive, and Adjust
Go back around and make sure that all the nuts and bolts are tight. Slide the jack back under the axle and lift the car off the jack stands. Pull the jack stands out and lowers the car. Now take it for a test drive. Make sure you load the suspension up by taking some good corners hard. Drive it like you stole it here.
Once you get back to where you did the work, raise the back of the car back up. If you need to, adjust the end links to provide for a stiffer or weaker sway bar. The holes at the very ends of the bars weaken it, while the holes closer to the thicker portion stiffen it. Once you’ve got it where you want it, loosen the nuts and bolts one by one and apply Red Threadlocker and tighten them back up.
Note: On my race cars, I drill the nuts and studs and insert a small cotter pin just like on tie rod ends and ball joints. This is just an extra layer of insurance against the nuts and bolts loosening while I’m out on the course and causing serious problems for me and other racers. When doing this, use a 1/16-inch drill bit and be careful to make sure you drill through the center of a flat spot on the nut.
Note: While pretty rare, there are sway bar kits for solid axle vehicles that have the sway bar mounting to the subframe and the end links attaching to the leaf spring mounting pad. Again, these are rare, but out there. Installation is similar to the regular solid axle.