Mopar torsion bar front suspensions ??'s

[rb70383]

I'm in the planning staging of the Duster and trying to decide on the front suspension mods. I don't want to go all crazy and redesign the front end on my 1st project. I came up with adjustable upper tubular control arms, boxed LCA's, and a heim jointed, adjustable front strut rod, with maybe the Fatman 2" lowered spindles. Is there anything else that can be do, any other tweaks? Of course bigger T-bars, but what about a redesigned LCA? Would this help at all? I don't think so. Would lengthening the front strut rod help any? That in itself would require some fabrication. I'm looking at firmfeel's nylon greasable LCA bushings, too harsh for street use? Want to keep it kinda simple for a 1st project, plus its the wife's car

[MrQuick]

Wifes car??? go with adjustable shocks.

[rb70383]

What?? Are torsion bars that much of a black magic or do they suck that bad???

[MrAngry]

Really depends on what you want the car to do? If you are lowering the car I would go with Magnumforce tubular upper control arms - they now make fully adjustable ones. These will solve any camber issues you have if you just crank the torsion bars down. You can also run oversize torsion bars 0.960 - really depends how stiff you want the ride to be.

[Norm Peterson]

rb - I don't see any real issues about the bars themselves, other than the selection of rates may be somewhat limited as compared with coil springs. But even so, fine tuning of wheel rate could be achieved with a light coil-over spring acting in parallel with the T-bar. Your shocks would then be matched to the total wheel rate.

Any redesigned torsion bar LCA would have to be able to safely resist a larger bending moment than would an LCA designed for coil springs, and perhaps be designed with greater bending stiffness as well (so that you don't give away too much wheel rate in LCA flex). Structurally, the T-bar LCA is a cantilever beam, while most LCA's associated with coil spring suspensions are beams simply supported at both ends and loaded at some intermediate location.

The combination of hard LCA bushings and a strut rod arrangement sounds like it could be a bit less than optimum. Depending on the specific locations of the LCA bushing axis and the strut rod chassis side pivot, the rod-ended strut rod could force the outer end of the LCA to move in an arc as seen in side view that a hard LCA bushing may not be entirely happy with. If the LCA bushings have their own ideas as to what that arc should be, this has the potential of stirring up the infamous 'b' word.

But I don't think there's anything here that can't be designed or tuned around.

Norm

[Bjkadron]

First off... All the suggestions everybody else mentioned are great.

About the strut rod, Its purpose is to control the forward/backward movements of the LCA. Mopar Performance recommends a urethane bushing. Urethane is really stiff stuff so I'd say save the money you'd spend on the heim joints and go with them and the stock rods(unless they are bent or something). Also If you keep the stock mounting points then I dont think you'll run into any of the misalignment problems Norm mentioned.

On the wheel rates, Norms Idea about the "helper spring" might be easier (and cheaper) then new torsion bars. If your getting new shocks anyway you might be able to use a coilover in the same place as the regular shock. Especially if you are using the tube uppers. Just another Idea to consider.

Redesigning the LCA would be getting really close to redesigning the whole suspension which I was thinking that you didn't want to do...

Hope this Helps!

[Norm Peterson]

Isn't MOPAR Performance oriented mostly toward drag racing? Reason being that things that work in that environment aren't necessarily the hot tips for others.

The motion at strut rod chassis side attachments is "multi-axis", even more severely than in stick axle rear suspension control arms. Polyurethane or any other stiff material is not a particularly good choice in such applications, as that requires more (significantly more in some cases) force to get the stuff to "squish" into the new shape that suspension movement requires than does the OE rubber. That said, it might be possible to do a little "creative drilling" to introduce more compliance into the "bad" bushing directions without throwing away all of the stiffness in the "good" ones (don't know for sure, but that approach does work with rear control arm bushings). Perhaps the MOPAR bushings address this already; if so I'd like to see a picture (it may be useful elsewhere as well).

(I wonder how deep this one was buried, I only vaguely remember it from the first time around)


Norm

[Bjkadron]

I'm not sure if this was a Drag racing tip or "all around" tip. I'll check where I found it and get back to you.
Mopar Performance is oriented towards Making MOPARS better... But you do have to sort through a bunch of drag racing stuff to find the info.

I'm not sure where it was buried but I was searching for "torsion bars" the other day and found it.

[Bjkadron]

Well I looked it up and Mopar recommends the urethane strut rod bushings for "road racing, solo, oval track, and drag racing" so I guess they figured out how to get them to not bind. I couldn't find a picture of them though. But I could send you a picture of my Energy Suspension bushings but I don't know if they are exactly the same as the Mopar ones.

Hope this helps!