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Torsion bar size: How big is TOO big?
#1718709
12/31/14 08:10 PM
12/31/14 08:10 PM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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I realize that feel is a subjective thing, but at what point do these 1.12 and larger T bars start to make the cars feel too tightly sprung?
I thought that I was doing well with the 1.0 bars in my car. I have a 70 Charger with an aluminum headed 440/493. Aluminum radiator, intake, TTI headers do shed weight as compared to factory stock. The battery is in the trunk. It rides nice, not too firm. I don't notice excessive brake dive. I have a custom 1.25 front sway bar with urethane bushings. The rear is MP XHD leafs with a 7/8" sway bar using rubber end links to reduce the slight oversteer the car had with the tighter urethane bushings. I've ran without the rear bar to reduce oversteer but I didn't like the extra body roll.
I understand that to reduce understeer, the rear needs more roll stiffness via bigger sway bar or stiffer leaf springs. Conversely, to reduce oversteer the front needs more spring rate or a bigger sway bar. The 1.25 is about as big as I can fit in there without touching the K member, so that leaves me with larger Torsion Bars.
The 1.12 and 1.15 ones from Bergman come at a decent price. My car went from .88 to 1.0 when I went from the 318 to the first 440 I had. It wasn't a direct comparison in terms of ride quality since I added weight to the car. As the car sits now, I'd expect the jump from 1.0 to 1.12 or 1.15 to be quite noticeable.
Mopar Mitch often chimes in to say ..." Make the switch to the big bars. You will not regret it". Thatis probably true in the case of an autocross car but what about a car like mine? I may autocross someday but I also drive on mediocre California roads. I had stiff springs in a 76 Camaro that would sometimes skip and skitter over rough roads, often understeering as the front bounced over the cobble like asphalt. I don't want to spend $300 to have a rough riding car that handles worse.
Opinions?
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Re: Torsion bar size: How big is TOO big?
[Re: Kern Dog]
#1718710
12/31/14 10:04 PM
12/31/14 10:04 PM
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Joined: Dec 2004
Posts: 801
central CT
cudazappa
super stock
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super stock
Joined: Dec 2004
Posts: 801
central CT
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Hotchkis has bars in 1.10" range. They've found that's the best compromise in ride and handling. They use their 1.25" hollow sway bar.
I run 1.18" with an aluminum headed small block and 1.125 solid sway bar. Next change in my front end is to go to better shocks and the hotchkis front sway. Currently my car oversteers a bit. The Bilstein Shocks feel to be beyond the limit of the torsion bars. The ride is stiff. Not skip across the road stiff, though.
Another thing to consider is fatigue of the chassis with stiff bars. The unibody can become the spring and that will stress all the hundreds of spot welds.
I used to run the 1" bars and found them much better than stock, but still soft. My jump to 1.18" was a vast improvement and right now, I don't want to go to 1.22".
1971 Challenger
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Re: Torsion bar size: How big is TOO big?
[Re: Kern Dog]
#1718711
12/31/14 10:34 PM
12/31/14 10:34 PM
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Joined: Jan 2003
Posts: 5,394
Pikes Peak Country
TC@HP2
master
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master
Joined: Jan 2003
Posts: 5,394
Pikes Peak Country
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IMO, you can't over spring a t-bar suspended mopar. However, you can certainly under shock it.
So previously, you stepped from .88 to 1, or a 22% increase. You also went from a 318 to a 440, or another 22% increase. Almost a net zero situation. Taking 50# off the engine for the aluminum bits, you still increased weight 15-17%, so as a percentage, you only realistically stepped up the wheel rate 5%, but you added a rear sway bar and ended up with a slight oversteer. Moving from 1 to 1.12 will step it up another 11% for about a 16% increase in total from where you originally started, so you may put yourself in a slight understeer position relative to where you are at now with the rear sway bar. So you may be able to swap back to the urethane bushings for the rear bar to level things out.
Given the way you like to dial things in, I'd almost wonder if a conversion to a splined tubular sway bar wouldn't be the better choice. Open up the K frame some(its not as strong as you might think) to allow up to 2.5" and pick up the pieces for a splined kit. Odds are you could put on together one for around $200. Swapping out the splined bar for more precise rates could be done for as little as $100, maybe less if you shop for used ones. Plus the options for end links may prevent any potential tire interference issues.
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Re: Torsion bar size: How big is TOO big?
[Re: Kern Dog]
#1718714
01/01/15 12:23 AM
01/01/15 12:23 AM
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Joined: Jan 2003
Posts: 28,068
Irving, TX
feets
Senior Management
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Senior Management
Joined: Jan 2003
Posts: 28,068
Irving, TX
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The Gas-A-Just shocks are the pieces that are hard to start moving but a bit soft afterwards.
A better shock would make a notable difference.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: Torsion bar size: How big is TOO big?
[Re: AndyF]
#1718716
01/01/15 05:12 AM
01/01/15 05:12 AM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Quote:
The realationship to watch is between spring rate and car weight (sprung weight). As the spring rate increases the natural frequency of the suspension goes up. If that frequency gets too high then the car becomes unpleasant to drive. The high frequency "jiggles" give me a headache but they cause other problems for other folks.
If the spring rate/car weight ratio is too low then the car feels like a boat.
You typically don't want to get the natural frequency of the suspension much over 1 Hz for a street car. You can go a little higher if you're willing to buy really good shock absorbers.
I know that I have read about this before but I'm not sure how to deal with it. The mention of "suspension motion frequency" confuses me! 
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Re: Torsion bar size: How big is TOO big?
[Re: Kern Dog]
#1718717
01/01/15 05:17 AM
01/01/15 05:17 AM
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Joined: Dec 2010
Posts: 12,375
SoCal
MuuMuu101
I got lucky at Woodward!
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I got lucky at Woodward!
Joined: Dec 2010
Posts: 12,375
SoCal
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Quote:
Quote:
The realationship to watch is between spring rate and car weight (sprung weight). As the spring rate increases the natural frequency of the suspension goes up. If that frequency gets too high then the car becomes unpleasant to drive. The high frequency "jiggles" give me a headache but they cause other problems for other folks.
If the spring rate/car weight ratio is too low then the car feels like a boat.
You typically don't want to get the natural frequency of the suspension much over 1 Hz for a street car. You can go a little higher if you're willing to buy really good shock absorbers.
I know that I have read about this before but I'm not sure how to deal with it. The mention of "suspension motion frequency" confuses me!
If you click "Attachment" I've inputted a small document that allows you to calculate wheel rate according to frequency. As far as frequency goes, I'm trying to think of a really good example...
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Re: Torsion bar size: How big is TOO big?
[Re: PHJ426]
#1718719
01/01/15 04:01 PM
01/01/15 04:01 PM
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Joined: Jan 2003
Posts: 5,394
Pikes Peak Country
TC@HP2
master
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master
Joined: Jan 2003
Posts: 5,394
Pikes Peak Country
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Quote:
I know that I have read about this before but I'm not sure how to deal with it. The mention of "suspension motion frequency" confuses me!
That is something you can get into as you get more in depth with information and wish to better understand all the interactions of the systems. Its not a prerequisite to setting up your car now.
Quote:
As far as frequency goes, I'm trying to think of a really good example...
A porpoising drag car is a good example of when frequencies are harmonized instead of complimentary.
I've also heard of guys setting up their cars with brand new, wiz bang, 300 different setting double adjustable shocks that do not understand the frequency situation and set all four shocks to identical settings. The net result a car that porpoises anytime it hits a highway expansion joint and produces a ride that is scary at anything over 50 mph.
Quote:
Search for "Torsion Bar Tango". It is an old article that I wrote a long time ago. It needs to be updated with pictures and illustrations but if you can wade thru it you'll get a handle on how to calculate the natural frequency for a Mopar front suspension.
This is an excellent starting point for a performance street set up. It can be found on Andy's AR Engineering site.
Quote:
After ducking under the suspension and really putting an eye ball on the torsion bar size in my Suburban.....I gotta measure thise.
After seeing that I kinda see what TC means. That and my Suburban came stock with 46mm Bilstein shocks and yes it handles well.
So Im thinking 1.24" for the Challenger
Yes, but don't forget the Suburban bars are also longer and supporting more weight, which supports the numbers in Andy's frequency article.
The origin of my comment is the fact that a 1.22 t-bar for a pre '72 B body is just shy of 400# of wheel rate. In Brand C cars, this equates to an 800# coil spring. Most street performance cars of this make are running spring rates that are starting at 600# and running upwards to 800#. Some competition cars are stepping up beyond that into the 1000# range. So the best we can ever hope to achieve with our mopars is very high end street performance.
One possible saving grace of all this is the current trend towards softer springs and bigger bars that would play into these lower available t-bar rates out there. However, these arrangements require infinitly more shock control than what is currently being offered in bolt on shocks for our mopars and would most likely require some specialized valving in a custom set up. They also need additional suspension travel, which would lead to rising ride heights , which doesn't always look great.
I think the reality in performance mopar handling is that we are ending up with moderate spring rates with moderate anti-sway rates and some pretty good shock options. This is where the Hotchkis development has landed with the best overall street/performance package. The old XV was there with their Level 1 packages before they folded. Copying either of these will lead to ver good results. Personal preference and application can also allow for adjustments up or down on the available rates out there.
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Re: Torsion bar size: How big is TOO big?
[Re: PHJ426]
#1718721
01/01/15 06:14 PM
01/01/15 06:14 PM
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Joined: Feb 2011
Posts: 4,302
Nebraska
72Swinger
master
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master
Joined: Feb 2011
Posts: 4,302
Nebraska
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Another "issue" I see with going big in T-bar diameter is it kills weight transfer and forward bite. The bigger the front bars, the less "effective" front suspension travel you will have. This is where we are at a disadvantage over coilovers IMO. Any BIG bar guys know what im talking about for example, jack the front of the car off the ground and look at how much suspension travel you have downward from where the adjusters actually touch their pads, this is travel lost in real world driving.
Mopar to the bone!!!
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Re: Torsion bar size: How big is TOO big?
[Re: 72Swinger]
#1718722
01/01/15 08:24 PM
01/01/15 08:24 PM
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Joined: Dec 2003
Posts: 22,696
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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"Another "issue" I see with going big in T-bar diameter is it kills weight transfer and forward bite."
Huh? You lost me.
In my world, in a balanced set-up, any weight transfer is less then ideal, why would that be an issue?
Last edited by jcc; 01/01/15 08:27 PM.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Torsion bar size: How big is TOO big?
[Re: Kern Dog]
#1718726
01/02/15 12:13 AM
01/02/15 12:13 AM
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Joined: Feb 2011
Posts: 4,302
Nebraska
72Swinger
master
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master
Joined: Feb 2011
Posts: 4,302
Nebraska
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Ok so I must be the only one that notices what a Nascar is actually doing at Martinsville? Im only relaying what I KNOW about my own car and the changes going from a .890 to a 1.06 in MY A body is my example. Some of you guys act clueless about what your suspensions are doing when you're beating the livin sh!t out of them. How big is to big you asked? From what EVERYBODY has said 100 times on B and E bodies, you cant go to big for good handling on those cars because the hexes are not big enough.
Mopar to the bone!!!
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Re: Torsion bar size: How big is TOO big?
[Re: 72Swinger]
#1718727
01/02/15 12:28 AM
01/02/15 12:28 AM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Nascar?
Who am I ? Ricky Bobby? I just wanna go fast! I see Nascar as something totally foreign. The stuff they use is so far removed from our stuff I see very little that we can learn from as it applies to a torsion bar and steering box car.
I have the 1.03s in my 360 67 Dart. That car rides fine. I guess with the B body torsion bars being 4 inches longer, it can be said that the wheel rate of a B body 1.12 isn't much different?
The Firm Feel site lists an A body 1.0 as a 195 WR, and the 1.06 as having a 252 WR.
The B body 1.12 shows a 275 WR so yes, that is a bit more. Not too much though I'd guess.
Last edited by Frankenduster; 01/02/15 12:33 AM.
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