To Rear Sway Bar or Not

[303Radar]

Looking for input, I've been tossing around whether or not I need a rear sway bar.
My rear axle is a Jag IRS from a 71 or 72 XJ12. It has four shocks, two on each side, one shock on each side of the half shaft. Some Jags had a rear sway bar, but it was 13 or 15 mm roughly 3/8th to 1/2 inch) diameter.

Here are pics from my build thread (http://www.348-409.com/forum/threads/ragans-59-el-camino-rebuild-project.27910/#post-245589 )


I've heard with a good spring rate, a rear sway bar is overkill. But I'm so used to seeing them, that there must benefit other than dead weight.

My main goal cornering ability, then ride comfort. I know the cheap answer is not to use one. But I don't think it would be too difficult to engineer one.

Normally I'd post this on a forum dedicated to Independent Rear Suspensions, but the one I use is fairly dead with very little traffic.

Any suspension expert or otherwise have an opinion?
Thanks!

 

[La Hot Rods]

My thought would be that you would want one if cornering was a concern.

 

[DonSSDD]

If you've gone to all the work of putting that jag rearend in there, I'd err on the side of caution and add the sway bar. Jags must have had them for a reason and your car likely weighs more than a jag with a higher center of gravity?

 

[models916]

Sway bar would allow softer ride without compromising handling on turns. Run a softer spring with the sway bar.

 

[yellow wagon]

I'd add a big sway bar just for handling reasons! Make that big girl handle like its on rails!

 

[303Radar]

If you've gone to all the work of putting that jag rearend in there, I'd err on the side of caution and add the sway bar. Jags must have had them for a reason and your car likely weighs more than a jag with a higher center of gravity?

The curb weight of the '72 Jag XJ 12 is 3880 pounds, the estimated curb weight (according to the GM Heritage Center) of the '59 El Camino is 3760. Weight wise, not a lot different, especially after a driver sits in.
I can't imagine the center of gravity is too different.

Sway bar would allow softer ride without compromising handling on turns. Run a softer spring with the sway bar.

I think this is the best reason of all!

I guess my next stop will be the U Pull and Pay. I've been looking at sway bars under trucks and jeeps and off hand, they look like good candidates. Or perhaps I'm too cheap for this:
http://welderseries.com/blog/online-store/sway-bar-kit/

Then again, I do have the front sway bar from my '83 El Camino, and that bad boy was 1 3/8th diameter. Not sure why I didn't think of this before. This would be easier to adapt then the rear sway bar from the '83. The rear used trailing/control arms which came in at an angle and I'm not sure I want to deal with making a bracket to overcome the angle.

Thanks for everyone's thoughts!

 

[Ishiftem]

Models is right. You can control body roll with a high spring rate, but ride quality will suffer and as will handling. Stiff springs will cause the tires to skip over road irregularities instead of following them. The tire can't do its job if its not on the ground! Also remember, the length of the arms and width of the bar all play a roll in what the rate of the sway bar is. Also, small changes in bar diameter make a huge difference in the rate. Even a 1/16 change in diameter can change the rate by as much as 20 percent.

 

[303Radar]

I did a mock up with the large front sway bar I have and I'm really tempted to use it as it will mount easily to frame and clear the shocks. I'm a bit worried though about its size, it really is 1 and 3\8ths in diameter. If I go this route, I may come up with a way to disengage it by rotating it upwards and lock it out of the way.
Here are some pics of a mock up


Here is a pic of the sway bar itself, it seems like a monster!

I'd like to use the smaller one but it won't clear the shocks easily and if I heat it to clear the shocks, it will lose the strength needed for a sway bar.

The other option, would be to see if I can take a piece of .120 wall DOM chrome moly, spline the ends and ends which slide on the ends and connect to the lower control arms in the same fashion.
This might be a good option if this sway bar proves to be too still.

 

[Don Jacks]

That large bar on the rear will require you to use a much softer spring,unless you really like "oversteer".The reason that they were bigger in the front was because that's where most of the cars weight was.

 

[La Hot Rods]

Have you checked out the Currie Anti Rock Bars?

 

[303Radar]

Have you checked out the Currie Anti Rock Bars?

I hadn't checked those out before. I took a quick look and design wise, I think they are what I'm looking for. I'll check them out closer later. Maybe I can find one in the right length which is cheaper.

I may buy a couple of these:
http://welderseries.com/blog/#!/Sway-Bar-Arm/p/49770102/category=12921498&forcescroll=true
and a couple of these:
http://welderseries.com/blog/#!/Splined-Coupler-3-4-36/p/51067658/category=12921498&forcescroll=true

I have a neighbor who runs a tool making business and see if he can spline a piece of DOM Chromoly. If so, this might be a cheap option.
Not that I really want to, but I could run the bar through the frame with an option like this.

Thanks for everyone's thoughts and input!

 

[Ishiftem]

That 1 3/8 is WAY too stiff for a rear. Potentially dangerous even. Take a look here. The arms can be heated and bent to whatever shape you want and then heat treated. There won't be enough material to spline a piece of DOM moly and not have it crack.
http://www.1speedway.com/

 

[303Radar]

While doing, I was behind a newer Dodge Ram truck and was looking at its rear sway bar. Looks like it is an inch or less in diameter and may be wide enough to clear the shocks. I have a slow day of work coming up. Think I'll hit the pull and pay with some tools and a.tape measure. If I can find one which is 42 to 46 inches wide selection, I'm bringing it home. It'll be nice to pull the bushings and all the connecting rods in one place.