Swaybars, learn me! I need a big one for Tunatruck

Hello hive!

As some of you have been familiar, I have been struggling with the swaybar for Tunatruck. I need a big one. The 1996 Suburban and the [late 90s GMT400] were both 1.25" diameter. They also were mostly straight other than the arms, which were a touch too short at 9 1/4" or so.

I can adapt to nearly anything else, but would prefer a style with the endlink bolt parallel to the road, in either axis really.

I think 1.25" is the minimum diameter, but I am pretty much guessing. I put another feeler out about the Expedition, but it's arms are too short and far apart to be useful (the control arm tapers, so the wider the bar, the longer the arms have to reach to get across the tie rod).

What do you know?

look for the swaybars that come on stuff like ambulances and box trucks, those are usually beefy.  will the swaybars from the diesel versions of tuna truck work?

Build your own ends and use a torsion spring from an ifs truck? Bonus points for keeping the key and adjuster built into at least one end.

Alternately, build a couple of rockers and some pushrods and use coilover springs?

Modify the best fit you can find?

I can modify, and have, but then had to redo based on moving the tie rods around.

The heavy-duty trucks did indeed use a swaybar which fits, sort of, but I don't like it. I'm looking for something better, and hollow preferably.

oldopelguy said:

Build your own ends and use a torsion spring from an ifs truck? Bonus points for keeping the key and adjuster built into at least one end.

Alternately, build a couple of rockers and some pushrods and use coilover springs?

OK idea number one is pretty neat, but hard.

tuna55 said:I'm looking for something better, and hollow preferably.

Isn't a larger but hollow bar going to be the same as a smaller diameter, solid bar? It seems like finding a smaller, solid bar would be easier than tracking down some huge, hollow bar.

Anybody know what kind of swaybar The Targa Truck is running?

In reply to STM317 :

Not really. As one engineering professor said “the middle is lazy”. One of the two I had is hollow. The weight difference is stark!!

In reply to tuna55 :

1) Torsional spring rate varies as the FOURTH power of diameter, so the middle contributes virtually nothing.

2) Flexure of the 'arms' contributes very little to the effective spring rate, but their length is really really important.

Same diameter bar with shorter arms is stiffer than one with longer arms.

A 3rd gen Camaro was available with a 38mm bar. I think that's the largest stock hollow bar I can find.

clshore said:

In reply to tuna55 :

1) Torsional spring rate varies as the FOURTH power of diameter, so the middle contributes virtually nothing.

2) Flexure of the 'arms' contributes very little to the effective spring rate, but their length is really really important.

Same diameter bar with shorter arms is stiffer than one with longer arms.

True and true!

Keep in mind that some sway bars are made from hollow tube, so not all 1.25" bars will be the same rate.

Edit:  I see that has already been covered

I heard that welding spring steel causes stress fractures.  Are there techniques to make that not happen?

In reply to tuna55 :

I used 4130 steel tubing bent to shape and took it to the local truck spring shop to be properly heat treated. 

Curtis said:

Keep in mind that some sway bars are made from hollow tube, so not all 1.25" bars will be the same rate.

Edit:  I see that has already been covered

I heard that welding spring steel causes stress fractures.  Are there techniques to make that not happen?

My materials guy at work says it's okay on the arms but would ruin the heat treat on the torsion bar itself and cause issues.

Would sway bars from a RV work, seems like they would have fairly large bars.

Hellwig makes them, might have one off the shelf that would work, ones below are for F450 based RVs.

Front

Rear 1.5"

How about a set of torsion bars from a VW/Porsche with arms welded on to the original end caps?

Loosecannon used some on his MGB-GT build and you can get them in various diameters and lengths on sites like CIP1.com and eBay, etc.

There are some tubular ones made.

This way you could more easily tune them by trying different bar diameters and arm lengths.

Just a thought.

In reply to Stefan :

Good call, but I think the diameters are too small for me., also, $$$ wow for bigger stuff.

In reply to 81cpcamaro :

Neat idea, but I think those may be solid, and also I still need dimensions for them. No RVs in any JY close to me.

Maybe you can contact Hellwig and get the dimensions directly from them. They probably are solid, no info showing any hollow bars.

my p30 rv front sway is big but solid.  it's also v heavy.  what about a hearse? or a limo? 

I gotta think that this is very DIY and budget friendly.

I would think about generic spring steel bar stock with your own ends.  You could have the ends splined and weld up ends using some old driveshaft yokes.  Or start with square or hex bar stock and use pockets from a torsion bar suspension; like the lower control arms from an IFS 4x4 truck.

Another thing you could use on splines is a whatchamacallit... like the way motorcycle shifters attach.  The internally-splined shift lever has a tightening screw on it so that it slides over the shaft and then clamps down on it.

Like this, but longer.

And some other photos for inspiration

Maybe take two of these in the correct size, have the bar stock splined to match, then cut the yoke part off and weld on arms for attachment

Or use the LCAs from a 4x4 truck and get hex spring steel bar stock

In reply to Curtis :

I love all of those ideas, but they are all dramatically more expensive than finding an OEM which will fit. I am going to spend $30 maybe on a used OEM swaybar. I am going to easily spend 10x that piecing together a sweet splined package.

I like the idea, but the budget can't cope!

Fifteen years ago I wrote the article about installing a big 1.25"  front bar on GM trucks. I included part numbers for over the counter urethane bushings and more. I think it's as relevant today as it was then.

Click here for the FAQ article

In reply to Cousin_Eddie :

Hey I saw that, and read it several times. I did buy the brackets and bushings, but I really really hate the design of that bar! Plus, my tie rods are below the spindle now, and the bar would run right through it anyway.