Technical Sway bar material question

Look up speedway eng. in Cali. They make all kind of bars , arms , and all the acc. Made a custom one for my cab over , real slick .

 

It depends. A car with coil overs surly needs one. The body is sitting on where the springs mount and that usually means a narrower support span and there fore less roll stiffness. I like to run a test. I support the car in the center of the rear axle and sit in the doorway and measure the drop. I do the same with the front supported. I add a roll bar to bring the rear stiffness up to match the front. They usually need more because of the weight forward so the back ends up stiffer in roll. I think my cars have handled pretty good. I do know it really improves the handling to have a rear bar.

 

Well, this has turned into a pretty decent pot of info. I know a thing or two about chassis set ups and initially just wondered aloud if a reliable bar could be made in the shop out of common materials.

My experience over the years is especially sedans can benefit from a rear bar. I also agree with ago. Adding a rear bar is not going to instantly make anything into a death trap. There are infinite variables on the way these early Fords are put together and what their owners consider a good handling car.

Good info, keep it going.

 

I put front bars on everything. I rarely put a rear bar on anything, unless it is a tail heavy-car, race car, or both.

 

Interesting, thanks

So coil over cars should have rear sway bars

As well as those equipped w/I beam



Has anyone tried chassis engineering or welder series front bar setup?




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To my mind sway bars are about adjusting roll stiffness. 50:50 weight split and equal roll stiffness front and rear means, broadly speaking, equal grip front and rear and neutral handling. Yes I know it's more complicated than that but shocks only make a difference in transition and I'm assuming we're talking about solid axles both front and rear here.

Roll stiffness is a function of cornering forces (equal both ends) and the distance between the roll centre and the centre of mass at each end. Now this is where it gets interesting because the centre of mass at the front of the car is lower than at the back end hence why the front spring mount is lower than the back.

What changes to roll stiffness are needed are determined by what changes you've made. Heavier engine? Cut the roof off?

On my car (ford anglia based) was originally a steel bodied saloon and was converted to a fibreglass body in 1961 I'm running a period rear sway bar kit to increase the rear roll stiffness. Since I've fitted it I get initial understeer (pushing) followed by power oversteer (loose) I've got a front bar I'm going to fit to see what effect that has but haven't got around to it yet. I've got a split solid front axle which lowers the front roll centre.

I'm also running a rear panhard bar so the rear transverse spring only has to carry the weight not take the cornering forces too. That one was a big improvement.

Suspension gets very complex very quickly!

P

 

Be aware, on a car with split wishbones on the front, the front axle acts as a sway bar already. If its a tube axle, its a much stiffer effect than an I-beam type axle, since an I-beam will twist much easier than a tube. Not so for four link fronts. Same for the rear, using split bones or ladder bars, however the 3" rear axle tube is MUCH stiffer than any front axle, increasing the rear sway stiffness to an almost rigid condition. That's why most ladder bar kits/setups pinch the front mounts together to reduce the "sway bar " effect.
....And yes, a rear sway bar will induce over-steer, and a front bar will induce under-steer (push). I've tried rear sway bars on asphalt oval track racers during testing, and it made the car wicked loose/ almost undriveable (over-steer).

 

I have made several from "Stress Proof" ground and polished, which is 1144 material. McMaster Carr has it, Cheaper than 4130 and easy to bend with the "blue wrench".

Rex

 

I've been working on putting a rear one I my car. That already has a Panhard rod and 4 link. The Panhard doesn't do much on the cornering per say, but control the rear axle sideways, that helps control the car at cornering. But has very little to do with roll when cornering.

But you shouldn't overdo the rear one, and you will have to have the front on. Or it will go totally out of whack.

The track folks over here ran stock front ones on the rear and a bigger one in the front, watt link and lowering springs.
To get a more neutral steer.
The rally folks ran a stock'ish setup and no rear swaybar.

 

The only thing high strength steel does for you is it can be twisted more before it takes a permanent set. If you design the bar so it does not twist past mild steel limits, it will be fine. I have run many mild steel ones and never bent one. See earlier post where I suggested testing roll stifness. You will find out if you need one.

 

Answer to OP question - Spark test will confirm - 5160 Alloy Steel.

 

Panhard bar locates the rear end. As I said putting a rear bar on a solid axle 32-34 is not going to make it a monster. You don't automatically need one on the front. A rear bar will reduce understeer. You can't compare what NASCAR does or any other type of chassis, to a solid axle hot rod. A rear bar or front bar does not do the same thing on every chassis. So these statements that you also need a front bar or a rear bar will make the car swap ends is wrong. Did any of you ever road race competitively? I have. You need to tune the chassis you are working on. Don't just throw things at it. I have tried a dozen different springs, shocks and bars on my 32 to get it the way I wan't it.

 

I road raced for many years. I'm also a suspension engineer.

 

If your car is understeering, Why would you put front bars on everything?

 

Regardless of what end of the car the bars are installed at, how do you calculate stiffness required for your car? and / or how long the ends (levers) and how does that effect the overall rate of the bar? I'm no engineer, but I would think it's important, eh? Do I throw a 3/8" or 3/4" or 2" bar at the problem? Hollow or solid? How long are the "levers" at the ends and how does that effect the rate? I've seen charts that rate torsion bars ICW various length splined arms, but not sway bars. I could see how the same charts might be usable for either type of bar, but I've never, ever seen a rating on a sway bar, just a "diameter." So how do you figure it out? Gary

 

I never build a chassis that understeers.

 

Gary, TCI lists a rear bar for a 32 chassis, I think it is 3/4" dia. I don't know the arm length. Like I said I disconnected my rear bar and did not like as much.

 

My last rear sway bar experiment was to put an early `90`s Dodge Dakota 2wd truck front sway bar on the rear of a banger powered `31 Murray Hiboy Sedan. This car has a dropped axle/split wishbone in the front, and coil-over rear suspension laid over 28degrees from vertical with a rear panhard. The car stiffened up in the rear, so the coil-overs were set to full soft. The car is more predictable and freeway friendly with this setup. However, Each Application HAS IT`S OWN NEEDS. Swaybar engineering, along with all other suspension work, is not a set of definite answers. Test carefully in a large parking lot with the mods that you do before going out and playing in traffic....

 

I noticed without a rear bar my 32, when you changed lanes quickly on an interstate at speed the car wanted to sway.

 

I am looking around for info regarding rear sway bars because I am considering one in my coupe when I ran across this thread...
I do not have a front sway bar but I am running a straight axle (tube) with four bar...I have coil overs in the rear with four bars back there too...
The car has too much body roll hense the need for a sway bar...
After reading some of the posts here I am nervous about adding rear only...

 

Check the front and rear roll stiffness. Jack up the back with the jack centered under the rear end and measure the drop when you sit in the door way. Do the same with the front jacked up. I like the rear stiffness higher than the front as the cars tend to understeer with the engine weight. A rear bar will reduce understeer. Mine is neutral with a 7/8" bar.

 

I don't know what they are made from but the one I cut and machined 3/4 square ends on was damn hard.. Used carbide end mill and sparks flew off when cutting.

 

Don't be afraid of running rear bar only. If you have too much body roll you need a sway bar. the car won't turn into a monster with rear bar only. try 3/4" with about 7" ends.

 

Well...I did it...
I searched and searched for something that would fit...
Figured if I could match something up I could do a used one, a take off from a modern car etc...
Then I ran across the Pete & Jakes rear sway bar, made to fit a 32 Ford frame, which I have and a Ford rear end, also which I have...
$175 and included everything needed...


Of course there was a few parts that I didn't use and of course I had to fab a bit but no biggie...

A few easy to moderate test turns and then a few more radical ones in an empty parking lot and then of course a few donuts Then down the road I went...The difference is amazing...
The car actually felt dangerous before and now it is rock solid and corners like a dream......
I felt so much better I could not get the huge grin off my face! LOL

 

If your car has hairpins and an I-beam front axle, then the front axle twists just like a sway bar. In that case, adding a rear sway bar may help even out the difference between the front and rear roll stiffness.

 

It was requested that I post a couple pix of the install so...here you go!
Great kit...great quality...powder coated etc...
It changed my car so much...the difference is like night and day, not just the body roll but the entire driving experience is tons better...
It drives like a slot car compared to before...highly recommended mod if your car doesn't already have one...