Technical solution to body roll with rear leaf spring setup

Hi guys --- new to this forum. I bought a 1930 Chrysler Sedan street rod a few years ago with a rear suspension setup of parallel rear springs with adjustable air shocks over a standard GM rear end and an original boxed frame. At highway speeds and in cornering, I am experiencing excessive body roll and instability. Looking for opinions on the best solution to control body sway without breaking the bank.

 

With a parallel leaf rear you shouldn't experience all that much body roll. I suspect that your front suspension could be inducing the instability. What do you have in the front, coils, leaves (transverse or parallel) a clip of some sort? You may need a sway bar in the front. I know this may sound counter-intuitive. Also have you checked the shackles and bushings front and rear for wear or looseness? Is alignment good? What tires are you using? It all comes into play.

 

if the springs are closer together than stock use a sway bar ....I think you should have a rear sway bar anyways

 

What style of "adjustable air shocks" ?

 

How big is the sway bar on the front of the car? or isn't there one?

 

Check these guys out.
http://quickorgarage.com/swaybar.htm
They make custom sway bars. I know a lot of guys that have used them for Fairlanes.

 

A single fill air shock system will allow the pressure to increase in the inside shock as the outside shock is compressed,thereby increasing the roll effect


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I like to test rather than guess. Jack up the front in the middle and put a rolling load on the car. Do the same to the back Which end let the car roll more? Stiffen up the weak end with a roll bar.

 

Like 32rules said. If the air shocks have a single fill point, they can act to increase body roll. The simple fix is to run separate fill valves on each side so that air being squeezed on one side doesn't lift the other.

 

Do you have a front and rear sway bar?

I'm thinking a good set of gas shocks might be a better alternative to the air shocks. HRP

 

Thanks for the advice - car has a Jag front end in it with coils and aftermarket shocks. Wheel alignment has been done and radials on both front and rear. Sounds like I should look into adding both front and back sway bars. Just not sure who I would go to supply them.

 

Salvage yard and a measuring stick, get the biggest diameter that fits! Gary

 

We need more info here!

If during bodyroll it is oversteering [ rear being loose, trying to spin out] the front is too soft.
If during bodyroll it is understeering [ front trying to push] the rear is too soft.

 

If XKE based I think there would have been an anti-roll bar in the box.
https://trevsfleet.files.wordpress.com/2015/02/img_4187.jpg
I don't know what to say about the coil-over. I was thinking XKeeez used torsion bars at the front.

 

I'd like to add.
If it is unstable in a straight line
As in twitchy/nervous in the steering, but you can feel it in the seat of your pants you might have the rear suspension set-up in "Roll-Oversteer"

If the front spring eye is higher than the axle centreline the axle will move backwards on an arc when compressed.
This causes the rear to steer in that direction causing weight to transfer to the opposite side [causing that side to compress ]
Roll oversteer feels like the car will fall over in corner entry [but will anti-squat on corner exit]

All leaf spring vehicles are set up with the front spring-eye lower than the rear spring-eye [the front spring-eye is usually at axle centreline height or lower]

Roll understeer is more desirable on a street driven vehicle

 

Lots of good ideas here, but one I'd like to add is; Front roll stiffness is always greater than rear roll stiffness. If rear is greater, in a corner the rear will break loose very suddenly and without warning, and you'll never be able to "catch it" with steering input.

 

Exactly this. If you run a rear bar, and no front bar, in a front-engine vehicle, you are going to be in for an uncomfortable surprise.

 

I agree with checking plumbing for air shocks first of all, if they are plumbed up together instead of seperately, excessive rear rollover is a given fact.

 

Generally this is correct, but sometimes the rears springs can be too soft [which is great for straight line weight transfer or cornering traction with an open diff ]
Cars with a soft rear try to carry the inside front wheel during a corner.

It is highly probable in this case that the front is too soft due to the high CGH of a Chrysler sedan compared to a Jag which the front end was vultured out of.

It is difficult for us keyboard commandos to diagnose with lack of info supplied so far