Rear Sway Bar Addition Questions

[Dibbons]

My project vehicle is a 1972 Satellite Sebring Plus (318 for the time being with 8 1/4" ring and pinion).

1) I read/heard years ago that adding a rear sway bar could be a danger if a front sway bar was not added at the same time. True/False/Maybe?

2) Would there be a problem adding a rear sway bar while retaining the original stock spring rate?

Foto represents what I have on hand (not installed yet)

Thank you.

 

[R/T Boy 67]

I would add a front bar at the same time. To much rear stiffness will induce oversteer, which is a bad situation. You need a good balance between front and rear.

 

[Kern Dog]

The factory set up production cars so that they handled in a safe manner. This meant that they tended to UNDERsteer when driven aggressively. This is a condition where the front tires lose traction before the rear. This is considered safe because the car can often be easily controlled by slowing down.
With this in mind, the factory never installed a rear sway bar on any car that did NOT already have a front sway bar installed. As stated, a car with only a rear sway bar will have a tendency to OVERsteer. This is a condition where the REAR tires lose traction before the front. In this situation, the rear of the car will slide when the car is driven aggressively and the car is much harder to control and to avoid a spinout.
Most cars with a front engine and rear wheel drive perform best with the following combinations:
Moderate springs and shocks, moderate front sway bar.
Firmer springs and shocks, Larger front sway bar, small rear sway bar.
Stiff springs and EXpensive shocks, Bigger front sway bar, moderate rear sway bar.

All conditions will result in a better balance of safety and handling as opposed to your current plan.
My 70 Charger is very similar to your car under the skin. I have 1.15 torsion bars, Bilstein shocks, a 1.25 solid front bar, HD leaf springs and a 3/4" rear sway bar and it still sometimes wants to oversteer. I had a 7/8" rear bar on the car for awhile and did not like it. The car wanted to hang the tail end out way too easily.

 

[Dibbons]

I wonder if the diameter of the factory '71-'72 front sway bars are the same, taking into consideration only the '72 models were factory equipped with a rear sway bar?

 

[Kern Dog]

Diameter of the bar is only one consideration.
If they are both the same diameter but one of them has longer "arms" and softer bushings, it will be less effective.
For example:
A 1970-81 GM Camaro/Firebird used a large 1 1/8" and a 1 1/4" front bar on the Z28 and Trans Am but the lever arms (The section between where it was mounted at the frame and where it was attached to the lower control arm) was a LOT longer than the A-B-E body Mopars. Because of that, the Mopar bars of the same diameter are a LOT stiffer.