Quote:
quote:Originally posted by dgc333
>Fact 1: The sway bar does not cause oversteer, I had the bar installed and the handling >remained neutral to slight understeer, you need a much stiffer bar to achieve an oversteer situation.
I agree but on the scale of gross understeer to gross oversteer increasing rear roll stifness by adding a swaybar(any size bar)pushes you in the direction of oversteer.
>Fact 2: The main difference(other than cost) is that the rear is a little(and I mean only a >little firmer). A sway bar effectively increases spring loading on each individual side.
A sway bar isn't supposed to increase the spring rate when both wheels hit a bump your "little firmer" is really only a function of the friction in the bar mounts and the differences in the rotational center of the suspension verse the rotational center of the bar fighting each other. You do see an increase when one wheel hits a bump the other doesn't. The real reason for the bar is to resist body roll.
>Fact 3: The Watts linkage ONLY keeps the axle from shifting sideways under latteral loads.(No >sway bar function here!
Agree, a pretty common suspension design.
>Fact 4: The tube inside the pressed steel twist axle is supposed to be dual function; keep the wheels straight, and work as a sway bar.
Chrysler has been using an internal tube in the stamped twist axle design since the early mid 80's to tailor the roll stiffness of the twist axle design. It's easier, cheaper and more easily tailored to the desired action than having a bunch of different axles or seperate bolt on sway bar assemblies.
>Fact 5: WHEN THE REAR "TWIST AXLE" DEFORMS IN TRYING TO ACT AS A SWAY BAR THE AXLE GEOMETRY IS >THROWN OFF AND CONTROL IS DIMINISHED.
>- MOST OF THE BAD STUFF OCCURRS WHEN THE CAR IS FULLY LOADED -
>- WIND GUSTS CAUSE THE VEHICLE TO SWAY ABNORMALLY -
>- CORNERING BECOMES MUCH TRICKIER, SWAY CONTROL LETS LOOSE, UNLIKE WHEN THE CAR IS UNLOADED
>(like the car has had too much to drink)-
The twist axle is a design compromise between a solid axle with leaf springs and independent rear suspension. It's used because it is cost effective, provides acceptable performance characteristics and has minimal impact on interior space. The roll stiffness can be tailored with an external swaybar, adding or changing an internal bar or by changing the design of the axle itself. You would be suprised at how much any suspension design distorts and moves around, it not something unique to the twist axle.
I can't really comment on "fully loaded" comment the most I have loaded mine is four adults and I find nothing unusual or unsettling at mostly legal speeds. I have had the car up over 100mph on the hiway and find it to be very stable an uneffected by cross winds (not that I have driven in a storm or anything).
I was unaware that any PT's came with a seperate rear swaybar and the Chrysler web page only lists front swaybars for all of the models. It could be that they made a running change by modifying the wall thickness or diameter of the internal tube and eliminated the external bar (has the same effect and wopuld have likely been done for cost savings) and over looked the marketing literature. When you get right down to it this information is included in marketing information for just that, marketing. It does not really mean anything anything, it's the overall design of the suspension that will determine how well the car handles, not that it does or does not have a sway bar.
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As always some people will defend what they have as good, I maybe in the same boat, but for my own personal experience.
(Without the bar) I drove to Las Vegas in my PT unloades - just me - typical high wind gusts and MANY 18 wheelers.
Two days later I drive back to LA with about 400 pounds in the back end and had more than one inciden