Coil-overs > torsion bars: the answer?

[Grim Jhaixus]

So I've been around on other Mopar forums (I'm new here) asking about things like why our cars have torsion bars and if the coil-over kits are truly superior and wasn't satisfied with the responses I had received, so I put the question on a shelf. Now that I'm finally pulling the 318 out I renewed my query to find it answered on a Porsche forum, so I'll share the important bit here with a link to the page because even though its a different car they make a lot of solid argument on this issue. I have searched here and found that generally the opinion is to upgrade the torsion bars and I support that but I think I'm going to have to try coils

My favorite part (complete with authentic typo) :

"Absolutely true that coil-overs require chassis reenforcement to work properly, however once reinforced the ride quality with coil-overs will be better than torsion bars all else being equal. This is the result of lower loads on the trailing arm bushings and hence lower friction in the pivots.

A coil-over spring puts spring force on the trailing arm very close to the wheel axle. The result is a load path the goes from the spring almost directly to the hub and wheel. This puts very little bending moment on the spring plate and hence very little load on the bushings at the spring plate.

With torsion bars the opposite is true- the spring plate carries a lot of bending force, as the load is on one end (the wheel) and the spring force is on the other. The bushing reacts to this force, meaning it is very highly loaded with torsion bars. Since friction is proportional to load the torsion bar suspension has higher friction. High friction results in poor ride quality and lower suspension performance.

This might not be a big issue if there were quality bearings at that location, but unfortunately we have bushings, even the best of which are relatively high friction."

The link to the page for more context on the issues and arguments and experiences of the people involved:

http://forums.pelicanparts.com/pors...uality-coilovers-springs-vs-torsion-bars.html

It's a good read.

 

[YY1]

Aren't porsche T bars on the rear?

On a Mopar, I'm pretty sure the forces discussed above are carried by the control arms.

Probably one of the reasons the control arm/shock tower in a Mopar is MUCH sturdier than on a gm or ford.

- - - Updated - - -

I for one, am a HUGE fan of the T bar.

Easy to service and user adjustable with a single wrench.

Also one of the reasons period Mopar cars handle so much better than comparable gm and fomoco products.

 

[Hemi Rebel]

They can get in the way of headers though. Thats a pain.

 

[Grim Jhaixus]

Porsche 911 are t-bar everywhere.

And the thing is our cars had the superior suspension 40+ yeas ago. he technology for coil-overs have come up and everything is easily adjustable now (depending on what you buy, of course) but as far as I can t-bars are the same. We can get different diameters, yeah, but are they really better than what everyone is installing in the modern high performance cars? We don't see t-bars at NASCAR anymore.

I'm here to learn about how to make my 41 year old car the strongest car it can possibly be. My question is coil-over vs t-bar. I still feel like I need more information.

 

[Cranky]

The 911 bars are mounted differently than the ones in a Mopar and are much shorter. Shorter springs (of any design) will generally make the vehicle ride more harshly. Also, how much are you willing to spend to bring our old cars more up to date? Even tho the Mopar system is old, it was engineered very well and it still works well today. You can even get beefed up lower control arms to get rid of the flex and better bushings to reduce deflection or spend thousands of bucks to update the whole system or just buy a 911. Nothing against the 911 because I like them too but working on one is something I don't like.

 

[nm9stheham]

^^^ My thoughts are similar. One of the factors in the Porsche discussion is the shortness of the Porsche t-bars. When they get that short, the contribution of the bushings to overal spring rate are a lot more than for a longer T-bar. And the weight on the Mopars is so much more than the Porsches that the bushing effects are watered down even more; it makes the T-bar torsional to bushing stiffness ratio a lot higher (so the bushing stiffness gets less important).

Coil springs are the same as they were 70-80 years ago; they are t-bars wound into a sprial BTW. So coils per se have not been improved.

The big advantage for coilovers is that they are so quickly tuneable in rate (ride height changes are a snap with either); just pop out one spring and put in another, and you have them in 25#/in rate increments. You can get the coils anywhere. We don't have those increments for the Mopar T-bars and they are limited in availability and they take more time to change. And, as a side effect, there is a lot of new shock development going on around coilovers, so you can get a wider range of shcoks and rates with coilovers now. That was not true 15 years ago. NASCAR and Rally and SCORE have all gone to coilovers for these reasons, not due to an inherent laws of physics advantage over T-bars.

T bars DO have an advantage in that their weight does not contribute to unsprung weight. You can get lower unspring weight than with coilovers with the T-bar design. The total weight is a wash but could swing in favor T-bars if hollow ones are used..... as in the Porsche.

The t-bars are an inherently a good design, but the technology has moved towards coilovers for non-technical reasons.

Now if you really are interested in your car's handling, you are going to reap more benefits from doing something about the leaf/live axle rear, or the steering system.

 

[benno440]

well i dont know how much in depth information i can give you, but i run coil overs front and rear, custom k member front and 4 link rear, i made some brackets welded from chassis frame that bolt up to upper coil over to strenghten that are, and the verdict is my 68 charger handles better than any new car i have been in, 0 bumpsteer, 0 to none body roll, stiff feel, give a yank of the steering wheel and i either end up in passenger seat or out the drivers window on the side of the road. awesome braking, heaps of engine bay room, lower stance, better geometry, lighter running gear, coolness. i also have subframe connectors body is so stiff, i put a jack under front corner and the back wheel lifts off the ground has 0 twist. hope this helps make your decision

 

[YY1]

Gonna have to agree.

If you want the handling of a 911, go ahead and buy a 911.

You'll have what you want and probably save a lot of money.

I personally LOVE the way 60s and 70's t bar Mopars handle.

Front end goes where you point it, minimal body roll, and it's easy to steer the rear with the throttle- just like a giant go-kart.

I used to make brand new mustang gt's chicken out on the twisty roads "drifting" around the curves back in the 80s and early 90's, before "drifting" was even in our vocabularies.

 

[Grim Jhaixus]

I don't want a Porsche, I had a VW once but I don't want to ever do that again, that said I use Bosch sparkplugs. The idea I can't have the car I've wanted since I was 9 (traded my prized 58 Vette HotWheels for a black 74 Charger HotWheels) and find benefits from competitor tech is absurd to me. This might be hard for you guys to read: I'm putting a Ford 9" in my Charger. I can list benefits over the 8 3/4" til next week. I'm putting in a Ford style power rack and pinion for the same reason that it is superior. I didn't buy a Torino for a reason. I don't like them. I'm wondering if I should mount in a 429 just for spite. You guys can go buy Porsches. I married my Charger. It will never stop eating money, I could put 1 mil in it and then it would need more. Oil, tires, brakes, paint, another engine, more suspension, more rust, the glass will get old, the plastic brittle, the metal weak. Did you put a cost ceiling on your car?

Back to the legitimate conversation: The weight being spread over the length of the t-bars I have heard before, admittedly I hadn't considered the possibility Porsche t-bars were drastically shorter in relation to the length of the car versus the length of my own car most likely because I am only familiar to the T-bars in my own car. Guys like benno440 there are why I can't put this argument to rest. Every time I come to find a 3rd gen B body with any mods at all I always see tubular k members with tubular control arms and coils-overs, it's been like 50% went 4-link in the rear. When I ask it seems I hear they have less wheel travel, more dampening on the inside on tight turns, tighter turning. I have heard that each system weighs less than the other, each system is stronger than the other, each system is easier to adjust.

Here's what I'm going to do for now: new bushings all around and the best shocks I can find. The rack and pinion I ope to have in by year's end. I'll just have to see how it improves before deciding if it needs to be changed.

As for the drifting, that's really cool, you got a vid up somewhere?

EDIT: Can't believe I forgot the rear! I've seen on this site that rear sway bars tend to cause oversteering? Have any of you guys had this experience, and if so/not were you otherwise stock or modded in the rear suspension?

 

[benno440]

bilstein shocks are good, viking shocks are good, change to tubular UCA's to get some better geometry

 

[Grim Jhaixus]

I will be forced to go all tubular eventually. 73-74 3rd gens don't have to option of partially tubular without going home made, or else my agonies over getting out my upper balljoints would've been an easy thing to forget. You know what? There is a fab shop up the street I'll ask about UCAs.

 

[benno440]

could of sworn magnumforce makes em for that year.

 

[Grim Jhaixus]

Yeah but only compatible with their magnumforce tubular frame.

I just daa-bull checked and the sold separately UCAs only fit 65-72 (a common issue) us red-headed step kids in the '73-'74s have to buy a full tube conversion.