Rear sway bar advice for a triangulated four bar

[jski67]

Hey all,

I'm finally getting my car (67 camaro) on the road and I think I need a rear sway bar. The issue is nothing on the rear of my car is stock or a modern kit.

It's minitubbed (actually major-tubbed LOL) with 2x3" frame rails about 31" apart. The coilovers only have about 28" of seperation (which I'm sure is contributing to the body roll)

I've been thinking that a splined rear bar mounted between the frame rails in front of the axle is the way to go, but wanted an opinion as to if the top of my shock mounts would be a good to connect the end links of the sway bar? You can see a pic of the mount below.

I'm hoping the shock mount would work as the rear axle is now powdercoated, so I'd rather not weld on it.

Or is it possible to get a custom "bent" bar made? It there an advantage to one over the other? Opinions?

Thanks!
Jason

https://static1.pt-content.com/images/pt/2012/06/56024a7d-1.jpg

[silver69camaro]

Most sway bar companies will build a custom bar for you. It isn't cheap, but it may be the only way to go. You can always use splined bars too, which can be more flexible in terms of packaging, but are expensive and heavy.

Where is your roll center? That will play a big role in bar size.

BTW, who bent those rails?

[exwestracer]

Looking at how much of that progressive spring is used up, I'm wondering if switching to a linear spring might solve a lot of the problem. If that is ride height with all the weight on the axle, I'm thinking your rear rate might be a tad soft....

[jski67]

Thanks for the responses guys...

Matt,
Not sure what the roll center is (literally and figuratively!) but I'll try to figure that out over the weekend :) A little backstory...I installed the rails and four bar back in 2002-03 before any repro rails or floor were available and I needed to replace the whole back half because of extreme rust. In other words, it really wasn't installed with performance in mind, more just functionality. I did a bunch of research back then and I think the geometry is ok, but I'm sure it's not as precise as what you build. The rails were made by S&W racecars and were originally for leaf springs (they have a front spring pocket which I'm using for the lower bars). Knowing what I know now, I would have bought your rear clip in a heartbeat.

Ray,
That's an old photo and I'm not sure why the springs were so compressed (there was probably 1000 pounds of tools and parts in the trunk LOL), but I've since changed them to 250lb linear springs which seem to ride pretty good. Good eye though and thanks for the input.

If I do go with a custom splined rear bar, do you think I could use the top holes of the coilover mount for the end links if there's room? Any concern?

Thanks again,
Jason

[Apogee]

You've got Matt and Ray to help with the technical aspects...


...BTW, who bent those rails?

...but when I saw the picture I thought, "Who kinked those rails?"

[jski67]

You've got Matt and Ray to help with the technical aspects...

...but when I saw the picture I thought, "Who kinked those rails?"

Ha, compared to the rusted, swiss cheese originals I thought these looked great! At the time, it was these or the Competition Engineering versions for a "direct-fit" rail...which is what I thought I needed.

Now that I've done it once, my whole minitub/rear suspension install definitely is one of those jobs that I would like to do over, but oh well, it's fine. Just instead of spending weeks planning and nervously cutting out small bits of metal, I'd let it fly with a plasma cutter, throw in a full clip and be done in a couple days! :)

[exwestracer]

The roll center height will be the intersection point of the triangulated links. If they're on top of the center section, the R/C should be plenty high. I'll defer to Matt (or someone else) on that one, he's done a lot more with 4 links in first gens than I have...

[jski67]

The triangulated links are are mounted on the front face of the housing, square in the middle on each side of the pumpkin (ford 9 inch). So that means a low roll center height?

I'm guessing that and the inboard mounted shocks is why the rear axle articulates like a rock crawler when backing out of my driveway. :)

[exwestracer]

The triangulated links are are mounted on the front face of the housing, square in the middle on each side of the pumpkin (ford 9 inch). So that means a low roll center height?

I'm guessing that and the inboard mounted shocks is why the rear axle articulates like a rock crawler when backing out of my driveway. :)

R/C is about what you'd expect with a panhard bar. Tri-4 links are usually somewhat higher. I won't go into the reasons for having the upper links above axle centerline, it's obviously working for you...

Just out of curiosity, what is the included angle (V) of the upper links? We may be edging up on a cause here....

[jski67]

Just out of curiosity, what is the included angle (V) of the upper links? We may be edging up on a cause here....

Not sure and I can't measure at the moment, but I'll check this weekend..and here's a build pic that may give you a rough idea. (the front mounts were eventually boxed onto the frame rail.

The lower bars are running straight inline underneath the frame rails.

Thanks again for your help!

https://static1.pt-content.com/images/pt/2012/06/c07e1429-1.jpg

[exwestracer]

Not sure and I can't measure at the moment, but I'll check this weekend..and here's a build pic that may give you a rough idea. (the front mounts were eventually boxed onto the frame rail.

The lower bars are running straight inline underneath the frame rails.

Thanks again for your help!

https://static1.pt-content.com/images/pt/2012/06/c07e1429-1.jpg

Is this something that the car has done since you built it, or is the "rock crawler" wiggle something that just cropped up?

[jski67]

Is this something that the car has done since you built it, or is the "rock crawler" wiggle something that just cropped up?

It's been that way since I started driving it, but I know I started with way too soft springs. Now that I've got 250s on it, I think it rides fine but it just seems funny to me that the axle articulate's so much while the body barely leans when slowly backing out of my driveway, going up hills etc.
In the front I've got 650 springs and a solid sway bar so my thinking was the front is "holding" the body roll, while the rear is articulating due to no sway and the somewhat inboard shocks.

[exwestracer]

It's been that way since I started driving it, but I know I started with way too soft springs. Now that I've got 250s on it, I think it rides fine but it just seems funny to me that the axle articulate's so much while the body barely leans when slowly backing out of my driveway, going up hills etc.
In the front I've got 650 springs and a solid sway bar so my thinking was the front is "holding" the body roll, while the rear is articulating due to no sway and the somewhat inboard shocks.

If you would, just to satisfy my curiosity, get a friend to help you and push side to side on the back of the car (bumper?) really hard. Watch the rear tires and see if they move around in the fenderwells.

Just wondering if your roll problem isn't a roll problem at all. I'd be more than happy to be wrong in this case.

[jski67]

Really pushed on sides this weekend and the tires did not move in the fenderwells at all.

I think I'm going to call a few manufacturers and see if I can't find a bent sway bar that will fit....after looking at it over the weekend, a bar that mounts to the bottom of the axle would work best as far as packaging.

[exwestracer]

Really pushed on sides this weekend and the tires did not move in the fenderwells at all.

I think I'm going to call a few manufacturers and see if I can't find a bent sway bar that will fit....after looking at it over the weekend, a bar that mounts to the bottom of the axle would work best as far as packaging.

Good to hear that there is no movement. Hope you find a bent bar that will work for that axle width. Don't go TOO big. Remember that bar is taking away traction at the rear in exchange for keeping the body level...