Running Without a Rear Sway Bar
- Thread starter AaronPaul
- Start date
Not entirely, which is why antiswaybars and the track bars are more important in a TJ than in a YJ. Pretty damned self-evident IMHO and why antiswaybars are run in well-built rock crawling TJs.
Pointing out that you are wrong does not make me an asshole.
english is my second language but i'm reading this as you are agreeing that he is right? what a turn of events!
Except in this case, Sri, Jerry is right.
Think of it this way - remove everything from a TJ except the spring. Control arms, track bar, etc., and you will agree that you can’t drive the rig. Because the coil springs alone can’t control the axle - or even keep it under the rig.
Leaf sprung vehicles only need the springs (and of course the attachment points and shackles) to operate.
That is the point Jerry is making - although sway bars do help on a leaf sprung vehicle exactly as they do on a coil sprung vehicle.
If you remove enough of the system you can make Jerry seem right, but this is apples and oranges. The leaf springs act as the CAs as well (more or less), so you can't really have a conversation comparing the motion of the two without including the relevant components.
In any case, I thought this was a convo about sway bars... It has nothing to do with how the springs move. The sway bar is just influencing the relationship between the body and axle.
The proper engineering term for a sway bar is an anti-roll bar, and I prefer to use that term because it is more descriptive of purpose. It's sole (edit: maybe debatable, so maybe "main" is a better adjective) purpose is to reduce body roll in a corner. It does this by coupling the left wheel's vertical movement to the right wheel's vertical movement. When both wheels hit a bump, there is no coupling, so ride quality is not heavily affected. However, when the body rolls, relative to the chassis, the coupling results in increased resistance to rolling (called "roll stiffness" in engineering vernacular). Roll stiffness is very important to vehicle stability in highly-dynamic situations (some idiot just cut you off, and you're both hard on the brakes and steering to avoid him). Anti-roll bars work pretty well, and they are on every car and truck on the road these days. However, since they work by coupling the left and right sides of the vehicle, they do have negative effects on suspension performance.
That being said, as a "reformed" vehicle engineer, the only way I'd remove either the front or rear anti-roll bars from my LJ is if I relegate it 100% to trail duty, and that trail duty is relegated to slow speeds. They really do add something to vehicle performance, even on a TJ. I run the stock front and rear anti-roll bars with JKS disconnects on my LJ because it won't be trailered to the trails. I didn't like how an AntiRock felt on the street, but I would like to evaluate the SwayLOC, as it seems like it might be closer to stock roll stiffness for the street.
I understand the point Jerry's making regarding leaf springs and coil springs, but it's not really relevant in the OP's question about running without an anti-roll bar. The suspension is designed with the type of spring in mind, so although the TJ has coil springs, they are not free to move due to the other suspension components.
That being said, as a "reformed" vehicle engineer, the only way I'd remove either the front or rear anti-roll bars from my LJ is if I relegate it 100% to trail duty, and that trail duty is relegated to slow speeds. They really do add something to vehicle performance, even on a TJ. I run the stock front and rear anti-roll bars with JKS disconnects on my LJ because it won't be trailered to the trails. I didn't like how an AntiRock felt on the street, but I would like to evaluate the SwayLOC, as it seems like it might be closer to stock roll stiffness for the street.
I understand the point Jerry's making regarding leaf springs and coil springs, but it's not really relevant in the OP's question about running without an anti-roll bar. The suspension is designed with the type of spring in mind, so although the TJ has coil springs, they are not free to move due to the other suspension components.
When I bought my TJ (with 3" lift) it had a stock front sway bar and no rear sway bar.
Addition of a rear stock sway bar noticeably improved on road handling.
Then I changed to a SwayLoc in front still running the stock rear. No change noticed in good on road manners. In off road mode, full articulation (9" to bumps at all corners) is easily achieved with a very balanced feel. AND it feels more stable than with the stock front sway bar disconnected.
Addition of a rear stock sway bar noticeably improved on road handling.
Then I changed to a SwayLoc in front still running the stock rear. No change noticed in good on road manners. In off road mode, full articulation (9" to bumps at all corners) is easily achieved with a very balanced feel. AND it feels more stable than with the stock front sway bar disconnected.
"Unstable" has a very specific meaning, no?
The inability of coil springs just by themselves to locate the axles is not the same thing as "unstable in all directions".
Whatever it is that Jerry meant to say, and what he actually said are two very different things.
I don't entirely disagree with this statement, but the sway bar offers a more controlled movement than not having one by slowing the roll, rather than a sudden unloading of a corner.
One of the biggest tells as to why they are good, when you watch the video I linked earlier, you can hear the pass rear tire start to rub on the fender just before he loses traction on the drivers rear. The roll bar was helping to keep the drivers side planted even while the weight of the jeep was shifting to the passenger side maintaining traction there.
But that was the point Jerry was making, I think. If the system allows the axle to move in every direction, instead of just up and down, I would call the unstable.
You happen to be in a very unique position. You have the means and opportunity to learn something that is very cool. With a proper tune and a bit of fiddling, you can dial in those DSC reservoirs to crank up the roll resistance enough with the low speed adjusters to easily drive on the street with some enthusiasm and nary an anti-roll bar in sight.
That can also be done with the high speed adjusters but the ride will get really firm to the point of discomfort. With the low speed adjusters tightened up, the small event harshness won't be mitigated as well and will become more evident, but as a learning tool, it is very much worth it to see just how good they are.
Can someone explain to me how the antisway bar locates the axle's position and defines its travel path? Or how an antisway bar stabilizes an unstable coil spring that isn't accomplished by the control arms and track bar?
I'm confused by the assertion because my old Antirock and my current Swayloc both use rod ends in the links. Maybe we need to be using bushings.
I'm confused by the assertion because my old Antirock and my current Swayloc both use rod ends in the links. Maybe we need to be using bushings.
I'm very much looking forward to finishing my build to play with those, but I have to start it in earnest, first! I'm a bit skeptical on adjusters, especially dual compression adjusters. In my other career, I spent a LOT of time at the shock dyno, in addition to track testing, and there are nine (that may be an exaggeration, but not by much) completely ill-effective adjustable shocks for every one effective one. However, I'm confident that, due to your influence, these will impress me!
The bushings on my rear swaybar were worn out when I bought it. After new bushings, on road stability was greatly increased.
Your examples are showing two different degrees of freedom (of movement). You can have three degrees of freedom and still be entirely stable. Ever see a spinning gyroscope?
In their respective regular range of motion, a regular chair and a rocking chair are both stable. Note that you can "rock" a regular chair on it's rear legs backwards and make it fall if you want to. Does it mean a regular chair is unstable?
As I said before "unstable" has a very specific meaning.