Torsion bars vs coil springs

[Brads70]

What tires do you recommend Brad?

Current tires are Falken Azenis 615K I'm happy with them. Not cheap though.... but you want to play you gotta pay. Not much selection in 15" that's why I went to 18"

http://falkentire.com/tires/passenger-car-tires/azenis-rt615k-tire

[HP2]

I assume this is a question of a modern coil-over suspension in comparison to torsion bars.

Others have hit some pretty key points of this. Similarities between the two systems are their ease of adjustability in ride height and ease of changing spring rates. While the springs themselves are not radially different in weight, many coil over systems are designed to utilize smaller and lighter frames mounting systems and rack and pinion steering, which does drop a lot of weight compared to a recirculating ball steering box. After that things continue to diverge pretty significantly.

Overall, the stock mopar design is very robust and was actually ahead of its time and outperformed nearly everyone one of their contemporaries of the day. Many manufacturers since then have changed over to torsion bar systems because of their benefits of low mass, easy adjustability, and improved geometry. The biggest shortcoming of the mopar design is the conjoined caster/camber relationship. This is the only flaw in an otherwise great set up and there are modern style upper control arms out there that will allow this problem to be easily addressed with improved caster angles without sacrificing camber angles. There is some debate about the mopar rear steer design vs front steer designs and how they push vs pull wheels through their arcs of motion. For most of us, this is a minimal issue that using quality parts can eliminate a lot of problems around.

Speaking of geometry, there is not a significant difference between modern coil-over and classic mopar systems. By contrast, early chevy and ford system had major problems with  positive camber gain, cumbersome spring/control arm interface, and uni-body structure to support them.  A couple of key factors in the mopar design that are found in most modern design are camber gains as the car turns. The outside tire gains negative camber as it compresses and the inside gains positive camber as it unloads. This improves tire contact patch while the body rolls. Mopars also have good ackerman angles, which allows the inside cornering tire to turn at an improved angle compared to the outside to minimize scrub and improve tracking through the turn. Some coil over systems do not have this at all. Mopars also have a reasonable anti-dive formula designed into them that matches many modern designs as well.

The biggest current drawbacks to the mopar torsion bar over coil overs is available rates and cost of those rates. There are only seven to eights different rates available and three, maybe four, decent performance handling rates for torsion bars and those come with a $300+ price tag. By contrast, coil springs are available in 50# increments from 100-1000 and are less than $100 a pair. If you are truly in a competitive environment where rate changes make a difference in winning, then a coil over would be preferred. Back in the day, this was not an issue, but now days it could be. However, for most of us, it is not a problem that needs solving because we don't need a variety of rate changes.  It also is not too troublesome to build a good system by choosing the t-bar/ s-bar front combo and then complimenting with the rear system to match. Leaf springs still have an infinite variety of rates that can be built into them.

[wes473]

  hello old thread, this seems like a good place to ask about the best recommendation for my 383 cuda suspension to keep her robust and fun cornering. Originally I was thinking about qa1 kmember swap but sounds like sticking with a stock design with adjustable uca, upgraded torsion bars and hw/joints? Hotchkis or pst or? Brads70 what magic stuff are you running?

[dodj]

The QA1 is a stock configuration piece. It is just more rigid. It still utilizes t-bars.
But it sounds like you know what you need to do with the suspension. Larger tbars - at least an inch, adjustable uca's are nice if you can afford them but non adjustable arms with more caster built in like the ones from QA1 are cheaper. Or my preference, the Moog offset bushings with original arms. Only set you back $50. Then add good shocks, and weld in some frame stiffening, a proper alignment...
Then 

[Brads70]

hello old thread, this seems like a good place to ask about the best recommendation for my 383 cuda suspension to keep her robust and fun cornering. Originally I was thinking about qa1 kmember swap but sounds like sticking with a stock design with adjustable uca, upgraded torsion bars and hw/joints? Hotchkis or pst or? Brads70 what magic stuff are you running?

The QA1 is a stock configuration piece. It is just more rigid. It still utilizes t-bars.
But it sounds like you know what you need to do with the suspension. Larger tbars - at least an inch, adjustable uca's are nice if you can afford them but non adjustable arms with more caster built in like the ones from QA1 are cheaper. Or my preference, the Moog offset bushings with original arms. Only set you back $50. Then add good shocks, and weld in some frame stiffening, a proper alignment...
Then 

I'd agree with dodj.
I kept the original k frame, just rewelded all the seams and added gussets for the steering box.
Here is what I did.....

https://forum.e-bodies.org/wheels-tires-brakes-suspension-and-steering/12/-using-c-body-spindles-on-an-e-body-and-a-body-lcas-and-viper-calipers/58/

[7212Mopar]

QA1 k frame saves you a lot of welding and gives you more clearance. I welded and reinforced my k frame awhile back long  before the QA1 came out to market. I do not have the know how and skills like Brad to go all out. Just standard mods with bolt on parts upgrade. Car handles great and can out turns many modern cars on the road. Seeing them disappear from your rear view mirrors after a few turns put a smile on your face.

[wes473]

  Thanks guys for your knowledgeable input, that just saved me a chunk of $ and a bit of time to get the mods done and driving her.

[soundcontrol]

@7212Mopar , I see you have an SRT also. I would like my -70's cars to handle like my 08 SRT Challenger.
How does yours compare?

[7212Mopar]

My SRT8 is a 2012 manual with the adaptive suspension, two modes, normal or sport. Suspension is stock, factory ride height and I got 295 tires at the back. The car weight like 4400 lbs and you feel the weight in normal driving and in spirited driving. It is a very comfortable cruiser and mostly fun around corners but not really a high performance cornering machine IMO. The Brembo brakes are wonderful and chassis is fairly good.

My 73 has a mixed of Hotchikis TB, front sway bar and adjustable shocks, PST parts, welded k frame and Bogerson steering box. I do not have torque boxes and any of the sub frame reinforcement, factory rear sway bar. I have Dr Diff 13" Cobra brake kit front and 12" brake kit rear. Good brakes but no antilock and not at the same level as the Brembo in terms of braking power and modulation. I think the car weights about 3400 lbs. So from start it is already a 1000 lbs lighter. The steering is tight and precise but not as accurate or fast response as a modern car. Much bigger turning radius than new cars. But it turns and brake way way better than stock. I can turn around corners just as good as the SRT and I have yet try to reach its limit. Car is lighter and sit lower than the SRT and that inspire more confidence. Brakes can lock up if you press hard enough. Car ride quality of course is not as comfortable as the new car. It rattles and squeaks, suspension is more stiff. Chassis is almost 50 years old so not very stiff.

Bottom line, my 73 is not a modern car but now is very fun to drive as what it is. Two weeks ago up in the hills, a newer AWD Subaru Outback was trying to keep up with me around the corners but just can't keep up. I have been enjoying and driving my 73 in the weekends much more than my SRT this summer.

Hope this help.

[soundcontrol]

Thanks 7212Mopar! I never driven an e-body that had all that done, and my restoration is slow, will be another few years.

I can really recommend subframe connectors, right before I took my 70 Convertible apart, I added them and drove it for a few months,
I noticed a huge difference in the car, before it was rattling and squeaking like all e-bodies, but after all that just stopped.
So I orderred the whole US CarTool kit and my car is being reinforced all over now.

[chargerdon]

I do not believe that Torsion Bars was done to save money.   Instead i believe they cost more !!   

I was 11 years old when Chrysler standardized Torsion Bars for all of their cars in 1957.   Back then I remember they were advertised as being a huge advantage over the Fords and GM's with their coil springs.   So for my money it was an advertising point for them !   Chrysler has always been known as an engineering company...   First american cars with Torsion Bars, Alternators instead of generators, heck they even had transistorized radios in my Dads 1960 Dodge Dart whereas GM didn't switch to transistors in the Chevies until the 63 and 64 model years.     

I also remember my father and Uncles all saying that the Torsion Bars not only out handled their Ford and GM counterparts but that they also all "rode better".    I agree with this, take a ride in say a stock 57 Plymouth or Dodge and then a stock 57 Chevy Bel Air and i think you will agree the Mopar's with Torsion Bars rode better than their counterparts. 

[FSHTAIL]

I have a small block 340 4 Speed car, I just went with 1.03 PST torsion bars, I wish I would have gone bigger. 

The right is great, I could deal with a little more firmness. 
But all in all, I love the way it is now, night and day difference call the qa1 shocks, crossmember, Borgeson box, qa1 arms, modified lowers. 

I also updated the wheel and tires to a 17-inch so I could use real performance tires versus limited 15" light truck tires or drag radials.   

[RUNCHARGER]

Nice review and it's still a Mopar!