Rear sway bar.

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Yeah, you're liable to read all kinds of mis-information on that subject. Anyway, here's my experience, rear sway bars are meant to limit the amount of body roll and do a great job of it. I would never again own a vintage Mustang without a rear sway bar, they are that good. I'd love to take someone who thinks they cause oversteer for a ride in my car, it corners extremely well, yet sticks like glue, with not even a hint of oversteer. Also, if they are so horrible, why do prety much all new cars come with them? To each his own, but until someone can really show me a car (any car) that works better without one, I'll stick by my experiences.
 
Can you run a rear sway with a Detriot Locker? My understanding was that this kind of freaks out the Locker...any input would be great because I would love a rear sway if it didnt screw up my rear....
 
as with any suspension modification, you need to try to get the best balance you can. most people that have issues when installing a rear anti roll bar usually install one that is too big for the front bar they are using.

as for using a rear bar with a locker, you can, but go smaller than you would otherwise. for instance if you were going to use a 3/4" rear bar on an open diff, then use something closer to 5/8" with a locker.
 
Supposedly my front is original GT equipment which i have no clue as what size it is supposed to be. Years ago I did but life, kids, work, living in Japan for 12 years and etc. I've forgotten some stuff. I remember reading an article in Car Craft that you may be able to find one off a car in a junk yard. I have no idea how junk yards operate nowadays (I've heard they're different.)
 
Yes a rear sway bar can cause undesirable handling (over steer). This can be very dangerous in a performance driving situation. Adding a rear sway bar adds to the roll stiffness in the rear, which makes the outer rear tire work harder and takes load off the inner rear tire in order to keep the car from rolling. This means that with a rear sway bar your car will have less traction at the rear wheels, but that will also give your car more traction at the front wheels. So depending on whether the fronts or rears let go first in a corner, the sway bars front and rear can help to adjust that.

One other thing to keep in mind is that leaf springs have a lot of roll stiffness due to their design. Depending on how many leafs, the stiffness of the bushings, etc. your car already has much more rear roll stiffness than a modern car with coil springs in the rear. The coil springs don't behave the same as leaf springs during cornering. There are many books out there about suspension design and far too many details to cover in a post here.

In general there are two philosophies for setting up springs and sway bars:
1. Heavy springs with light sway bars
2. Lighter springs with heavier sway bars.
The reason I say this is to let you know that the springs and sway bars are not independent. They have to be considered together as with all suspension components. If the entire system isn't taken into consideration the car may not function well. That also includes shocks and tires, of course.

A couple other points for clarity; I am not disagreeing with any of the other posters on this thread.
1. The factory set up our Mustangs to understeer, because this is safe for non-expert drivers.
2. Adding some roll stiffness in the rear MAY help to reduce the factory-designed understeer and improve your car's handling, depending on what exact components you have on the car.
3. As stated above, the correct changes to both front and rear suspension must be done so they work together properly to make your car handle well.
 
I can see you've really thought out your response, but here's a couple points I disagree on: any sway bar, front or rear doesn't add load to the outer tire, it actually helps spread the load to weight the inner tire, that's how it reduces roll. You can prove this to yourself by jacking up your car by one corner. If you try jacking up (for example) one front corner on a car with no sway bar at all, only that corner will rise, because the load is only carried on that one corner. But with a sway bar, both corners rise because the weight is redistributed by the bar. Also, while leaf spring suspension does limit the amount of lateral movement better than coils, it doesn't add any roll reduction over coils. Sway bars are standard equipment on lots and lots of new SUV's and trucks even today. Both my Suburban and my F250 came right from the factory with a rear sway bar and leaf spring suspension in the rear, and both will out-corner any original, vintage Mustang. I also believe our cars were not set up with anything in mind but cost reduction. Every stock Mustang (Shelbys don't count) built before '69 handled horribly, even to the point that I consider stockers unsafe, so thinking the factory had some all-knowing purpose behind a car that had a ton of understeer is more of an excuse than anything. They also had 14 inch bias ply tires, yet I see very few people willing to live with that. You are 100% right in saying that considering the suspension as a whole system is crucial to being happy with your car. Springs, shocks, sway bars and alignment all needs to be planned ahead of time and fine-tuned to get the most out of it without a bone-crushing ride when you're just loafing through town on Sunday with your family in the car. Balance is what it's all about.
 
Playing with spring rates won't redistribute weight left to right, you can't control lateral weight transfer by increasing or decreasing the spring rate. Increasing and decreasing rate generally causes the other axle to decrease or increase load, with the opposite effect on the axle the rate was changed at. The same load is transferred laterally, but it's carried more by front or rear depending on the increase/decrease of rate.
And the reason a lot of people don't run anti roll bars on a leaf sprung suspension is the leaf acts as one itself, it has a different rate as it experiences warp. Now with springy factory bushings a lot of that warp disappears into the bushings, but as you increase bushing durometer that warp begins to act more. What most seem to find is that once you've stepped up the leaf rate and gone to stiffer bushings, you've already got the all the roll resistance you want. That's also why some stock vehicles have bars, big springy bushes help with ride but reduce the springs response in warp.
 
I can see you've really thought out your response, but here's a couple points I disagree on: any sway bar, front or rear doesn't add load to the outer tire, it actually helps spread the load to weight the inner tire, that's how it reduces roll. about.
I assume this was directed at me. It doesn't take too much thought to respond in generalities like I did. I tried to keep it simple.
Please think about your first statement more. The car when going around a corner wants to sway towards the outside of the corner, just like you do inside the car. Just think about it, if you want to prevent yourself from swaying toward the outside of the corner (when you're inside the car turning a corner), you're going to want to push down with the hand that's toward the outside of the corner. You don't need or want any push from the side of your body that's to the inside of the corner. The sway bar whether front or rear does the same thing. It pushes harder on the outer tire and lifts the inner tire. I can easily find pictures of cars that lift the inside front or rear tire going around a tight corner. That is what a very heavy sway bar (or excess roll stiffness in the suspension) will do.

If you try jacking up (for example) one front corner on a car with no sway bar at all, only that corner will rise, because the load is only carried on that one corner.
Sorry but I also disagree with this. It depends on the spring rates, weight of the car and roll stiffness whether only one corner will rise or not, especially in a leaf spring car. I can jack on one corner in the rear of my '70 convertible and both rear tires will come off the ground. I don't even have especially stiff rear springs or bushings. The rear of the car is light enough and the leafs have enough roll stiffness that both tires come up.

Also, while leaf spring suspension does limit the amount of lateral movement better than coils, it doesn't add any roll reduction over coils..
The first part of your statement is true, the second is absolutely false.

I also disagree with your statement that understeer is unsafe. Most every car on the road today understeers from the factory, because it's safer than oversteer. That's also why tire dealers always want to put new tires (if you're only buying two) on the rear of the car - even on front wheel drive cars. It's best to have more traction at the rear than the front of the car, especially for non-expert drivers. This includes 99% of people. I understand most guys (including me) think they are good drivers, but oversteer is unsafe for almost all of us.

I do agree that many modern vehicles have rear sway bars. You got that right.
 
Here's how sway bars spread the load: if the car is turning , physics dictates that more of the load will always be on the outside tire, right? The side of the car on the outside will travel down towards the bump stops because it now has more weight. Now suppose you add a sway bar into the system. As the outside of the car tries to travel downward, it's pushing on the end of sway bar as well as the spring. The other end of the sway bar is connected to the spring and tire on the inside of the corner, as the outside of the sway bar gets pushed down by cornering forces, so does the inside, right? What happens when we push down on the inside of the bar? It adds force (or a greater percentage of the car's weight) to the inside by transferring the force from the outside. As for the example you used of one front corner coming up in a turn, there are lots of them out there. I'm not talking about the ones where a car hit a curb on a road course (as in Sears Point) but rather than when a car actually lifts the inside front exiting a corner. This is because the car lacks balance and the rear is too soft or the front is too stiff and the car is weighting the outside rear too heavily. It might help to thing of a car as being a table: which table is going to be more secure, one with all it's weight on one side or one with the weight evenly distributed? That's the principle of sway bars and whether you believe me or not, that's why 100% or all road race cars have them on both ends. In fact every Pro/Stock drag car I have ever seen had a rear sway bar and they don't even go around corners! But because the rear bar evens out the weight load between the tires, it prevents one tire from unloading and loosing traction. I don't know what your current sway bar setup is, but try this: if your car has a decent front bar (1" or bigger) push down on one corner and observe what happens to the opposite. If you want to have someone measure it with a tape. With the bar connected, the corner opposite the one you pushed on WILL drop as well. How can that be? You didn't push down on that side, yet it moved! How did that happen? Because the sway bar (not shocks or springs) transferred weight to that corner. Hey run your car however you like, hell take all the sway bars off if you like, but although you may not believe it, sway bars increase rear grip by making both tires work. BTW, as for the unpredictable over steer everyone always claims, I have never seen it on either my '68 fastback or my '88 GT ( both have rear sway bars) even under the friskiest cornering. They can both bring the rear out under power in a corner, but they also are extremely easy to control, not twitchy or scary in the least.
 
Here's how sway bars spread the load: if the car is turning , physics dictates that more of the load will always be on the outside tire, right? The side of the car on the outside will travel down towards the bump stops because it now has more weight. Now suppose you add a sway bar into the system. As the outside of the car tries to travel downward, it's pushing on the end of sway bar as well as the spring. The other end of the sway bar is connected to the spring and tire on the inside of the corner, as the outside of the sway bar gets pushed down by cornering forces, so does the inside, right? What happens when we push down on the inside of the bar? It adds force (or a greater percentage of the car's weight) to the inside by transferring the force from the outside. As for the example you used of one front corner coming up in a turn, there are lots of them out there. I'm not talking about the ones where a car hit a curb on a road course (as in Sears Point) but rather than when a car actually lifts the inside front exiting a corner. This is because the car lacks balance and the rear is too soft or the front is too stiff and the car is weighting the outside rear too heavily. It might help to thing of a car as being a table: which table is going to be more secure, one with all it's weight on one side or one with the weight evenly distributed? That's the principle of sway bars and whether you believe me or not, that's why 100% or all road race cars have them on both ends. In fact every Pro/Stock drag car I have ever seen had a rear sway bar and they don't even go around corners! But because the rear bar evens out the weight load between the tires, it prevents one tire from unloading and loosing traction. I don't know what your current sway bar setup is, but try this: if your car has a decent front bar (1" or bigger) push down on one corner and observe what happens to the opposite. If you want to have someone measure it with a tape. With the bar connected, the corner opposite the one you pushed on WILL drop as well. How can that be? You didn't push down on that side, yet it moved! How did that happen? Because the sway bar (not shocks or springs) transferred weight to that corner. Hey run your car however you like, hell take all the sway bars off if you like, but although you may not believe it, sway bars increase rear grip by making both tires work. BTW, as for the unpredictable over steer everyone always claims, I have never seen it on either my '68 fastback or my '88 GT ( both have rear sway bars) even under the friskiest cornering. They can both bring the rear out under power in a corner, but they also are extremely easy to control, not twitchy or scary in the least.
I didn't read your post since it didn't start with, "oh yeah I guess I got it wrong."

Some people shouldn't post in tech sections.
 
Here, let me add some gasoline:
- Rear sway bars on a Mustang really change the way the car feels and the way you drive it. For best results, the first rule of sway bars is to make the rear one smaller than the front one. For instance, a 1” in the front will work best with a 5/8” to ¾” in the rear. I can’t emphasize enough that a rear sway bar really changes the way the car handles, especially if you do not know how to drive with one. If you do not accelerate through corners and step up the aggressiveness of your driving, the rear sway bar will make the handling feel loose and uncontrollable. The thicker the bar is, the more noticeable this issue will become. The thing that people need to realize is that unlike a front sway bar, you need to decide if you will be running a rear sway bar when you select your springs. The stiffer your springs are, the more noticeable the effects of the rear sway bar and the more aggressively you will need to drive. By softening the springs, you can get a little better handling with the sway bar without as much need for aggressive driving. The other thing to consider is that, unless changed to IRS, the rear suspension on a Mustang is a solid or “live axle” and the rear end itself acts much like a rear sway bar so this is why adding more stiffness and tying the two sides together further is not always better.

From the Daze cars website:
http://home.bresnan.net/~dazed/suspension101
 
Wow, I didn't realize my car was so dangerous until I read this. I don't even know how to respond to Hack's trash-talk so I won't. But here's my final thought on the whole sway bar thing making your car worse: don't put on on your car. Go on through life thinking your car is perfect and that it is as good as it gets handling-wise and the only reason 100% of every performance car built today, regardless of rear suspension design has one is because the engineers, designers and drivers are not as enlightened as you are. Tell yourself your solid axle is a sway bar, convince yourself body roll is the key to safe handling. Open minds like this is exactly what makes this site the joke it is.
 
Geeez... It's just a tuning device. There are too many variables to say for sure do or don't use one. It's $100 and an hr to install (if you're drinking and smoking). Just try a 1/2" bar and if you don't like it, sell it on flea bay. You'll have first hand knowledge at the end of the day. I've spent more than that putting gas in my truck . It's about preference anyway. Shoot, I don't even like leaf springs anymore.
 
As the outside of the car tries to travel downward, it's pushing on the end of sway bar as well as the spring. The other end of the sway bar is connected to the spring and tire on the inside of the corner, as the outside of the sway bar gets pushed down by cornering forces, so does the inside, right? What happens when we push down on the inside of the bar? It adds force (or a greater percentage of the car's weight) to the inside by transferring the force from the outside.
Swaybars don't work that way. You aren't pushing down on the bar, the car is pushing down on the springs. The outside control arms are pushing up on the bar. So when you corner , the outside of the bar is being pushed UP and the inside is being pushed up a certain amount depending on how stiff the bar is, keeping the inside edge of the car down. But as stated above, if it's too stiff then it will pull the inside tire up with it.