Torsion Bars?

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DentalDart

DentalDart

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Just upgraded my suspension system bushings all to PST Polygraphite. new front PST sway bar, new KYB shocks, new wheels and tires all the way around, I have a rear sway bar I want to install as well (I think I'm missing the attachments that bolt to the frame to connect the sway bar to).

I currently have 892/893 standard 340 bars
And I have these but I cant read the markings on them

20200111_135342.jpg
 
DentalDart said:
Just upgraded my suspension system bushings all to PST Polygraphite. new front PST sway bar, new KYB shocks, new wheels and tires all the way around, I have a rear sway bar I want to install as well (I think I'm missing the attachments that bolt to the frame to connect the sway bar to).

I currently have 892/893 standard 340 bars
And I have these but I cant read the markings on them

View attachment 1715454989
Click to expand...
Looks like 225 USA and 224 USA to me
 
Sway-a-Way too offers some more options for diameter/spring rates. They were extremely helpful to me.

How do you plan to drive this car? What kind of wheels/tires do you go for? Which shocks?

dukeboy_318 said:
Yep and they have been known to soften over time too
Click to expand...

Getting old is the worst. :D
 
MRGTX said:
Sway-a-Way too offers some more options for diameter/spring rates. They were extremely helpful to me.

How do you plan to drive this car? What kind of wheels/tires do you go for? Which shocks?



Getting old is the worst. :D
Click to expand...

I'm a sway away distributor and keep their bars in stock.
 
MRGTX said:
Sway-a-Way too offers some more options for diameter/spring rates. They were extremely helpful to me.
How do you plan to drive this car? What kind of wheels/tires do you go for? Which shocks?
Getting old is the worst. :D
Click to expand...

Wheels 15×7 steelies with 245/60 rear cooper radials and 225/60 fronts.
Shocks KYB
How I drive the car? To get donuts with my daughter doing burnouts around the corner (she loves when we spin the tires ha). Mostly just regular to and from daily driving to different places with a little spirited driving sprinkled in.

No track days for me.

20200111_130114.jpg
 
BergmanAutoCraft said:
Considering the work you've just completed, you may want to consider upgrading the bars. One of the biggest downfalls of the original design was not enough spring rate. You might want to take a look - Mopar A Body Torsion Bar Set 1.08" - Bergman Auto Craft
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Is there fancy ways of calculating the exact size bar I should get? I see guys running .92 and love them,1.00 and love them, 1.03 etc etc. Should I drive the car and see how it feels and then buy softer or stiffer bars? I dont deciding about things I dont know about :(
 
Yes, we did it when I was at XV Motorsports - we rented a four post tester and ran tests on the suspension and recording the suspension movement, geometry, etc.
I chose the T bar rates I carry based on all my experience to make things easier for anyone trying to make a choices. The other half of choosing t bars are the shocks. Shock rates seem to be a secret that the manufacturers hold close to their hearts...Again, my offerings are based on my knowledge and experience.
 
Going to the grocery story, doing burnouts ?
As long as they are clean, with no nicks, run the Mopar 340 bars until they prove you wrong.
 
Johnny Dart said:
Going to the grocery story, doing burnouts ?
As long as they are clean, with no nicks, run the Mopar 340 bars until they prove you wrong.
Click to expand...

Yea my daughter thinks it's the best thing ever when we punch the gas from a stop. The smile on her face is contagious when we let it rip.
 
DentalDart said:
Wheels 15×7 steelies with 245/60 rear cooper radials and 225/60 fronts.
Shocks KYB
How I drive the car? To get donuts with my daughter doing burnouts around the corner (she loves when we spin the tires ha). Mostly just regular to and from daily driving to different places with a little spirited driving sprinkled in.

No track days for me.

View attachment 1715455175
Click to expand...

The fresh steelies look fantastic.
I gather that the Cooper Cobra tires are just about the same as he BFG Radial T/A and the MT Sportsman ST(?), they're all all-season tires...but they look sharp. My father has a brand new set on his '67 GTX (white letters in) and I think they look better than my BFGs. I hope they perform well for you!

Johnny Dart said:
Going to the grocery story, doing burnouts ?
As long as they are clean, with no nicks, run the Mopar 340 bars until they prove you wrong.
Click to expand...

DentalDart said:
Yea my daughter thinks it's the best thing ever when we punch the gas from a stop. The smile on her face is contagious when we let it rip.
Click to expand...

Ha! That's great. You're raising that kid right! :D
It doesn't sound like you need a super stiff bar. I tend to agree with Johnny Dart on this one. The stock 340 bars would probably be just fine. He makes a good point about the bars being free of nicks. The vast majority of the stresses on these bars is carried on the very outer portion. A nick or a gouge could lead to a failure.

I will also just add that a lot of people have pointed out that even the "performance" bars from back then are much more softly sprung than we're used to from modern cars. If you're replacing them, maybe go a notch or two more stiff. I have 1.14" bars in mine. They're on the stiff side but even these are not uncomfortable (paired with Fox/Hotchkis shocks) IMO.
 
MRGTX said:
The fresh steelies look fantastic.
I gather that the Cooper Cobra tires are just about the same as he BFG Radial T/A and the MT Sportsman ST(?), they're all all-season tires...but they look sharp. My father has a brand new set on his '67 GTX (white letters in) and I think they look better than my BFGs. I hope they perform well for you!
Ha! That's great. You're raising that kid right! :D
It doesn't sound like you need a super stiff bar. I tend to agree with Johnny Dart on this one. The stock 340 bars would probably be just fine. He makes a good point about the bars being free of nicks. The vast majority of the stresses on these bars is carried on the very outer portion. A nick or a gouge could lead to a failure.

I will also just add that a lot of people have pointed out that even the "performance" bars from back then are much more softly sprung than we're used to from modern cars. If you're replacing them, maybe go a notch or two more stiff. I have 1.14" bars in mine. They're on the stiff side but even these are not uncomfortable (paired with Fox/Hotchkis shocks) IMO.
Click to expand...

Thanks! the steelies are from an 88 diplomat. My daughter and I then sanded, primed and painted them. Tires have grown on me, I have a set of bf's from 2010/2011 that have great tread just older and needed to replace them, the coopers were much cheaper. I have no space in the rear wells now so that's a problem I'll have to combat.

The bars seem to be in good shape just these weird paint bubbles on both sets. Maybe I will run the 340 bars for now then switch them out when I get new springs.
 
DentalDart said:
Thanks! the steelies are from an 88 diplomat. My daughter and I then sanded, primed and painted them. Tires have grown on me, I have a set of bf's from 2010/2011 that have great tread just older and needed to replace them, the coopers were much cheaper. I have no space in the rear wells now so that's a problem I'll have to combat.

The bars seem to be in good shape just these weird paint bubbles on both sets. Maybe I will run the 340 bars for now then switch them out when I get new springs.
Click to expand...

245 is a lot more tire than these cars came with. If you're trying to get down the drag strip, there are slicks in that size that will do the trick. Personally, I'm not a fan of tubbing a classic car unless it's a really serious build but it's your car of course. :)

As for the bubbles on the torsion bars, is it just paint? Pitting/rust in the metal could be a safety concern. Why were they painted to begin with?

The sway-a-way bars that I have are powder coated but I'm pretty sure they're usually bare. Maybe someone can correct me on that.
 
MRGTX said:
245 is a lot more tire than these cars came with. If you're trying to get down the drag strip, there are slicks in that size that will do the trick. Personally, I'm not a fan of tubbing a classic car unless it's a really serious build but it's your car of course. :)

As for the bubbles on the torsion bars, is it just paint? Pitting/rust in the metal could be a safety concern. Why were they painted to begin with?

The sway-a-way bars that I have are powder coated but I'm pretty sure they're usually bare. Maybe someone can correct me on that.
Click to expand...

Sorry forgot to add pictures. It doesn't seem like rust, it's weird. It's on both sets. Hopefully you can see it in the pictures, I could on my phone at least.

20200120_093515.jpg


20200120_093522.jpg


20200120_093527.jpg
 
I honestly wouldn’t run anything less than 1” bars on anything. The original torsion bars were sized for bias ply tires. Even if you run radials in the same size as the factory tires you have more grip and need larger bars. Even when I just had 225/60/15’s on my Duster it was undersprung with 1” bars and no sway bar.

Bergman Autocraft has great choices for torsion bars. The PST 1.03’s are popular because of their pricing and they’re a good size for a street car. Firm Feel and Sway Away make good bars as well in various sizes.

All of the original bars are like 45+ years old at this point. While they may be ok, they were never intended to be in service that long. They do fail, and they can fail catastrophically. For a car that will see frequent street use I think they should be on the list of stuff that gets replaced. Firm Feel offers a reconditioning service, they shot peen and re-heat treat the original bars. That would be useful for someone doing an OE restoration, but otherwise I’d just replace them.


dukeboy_318 said:
Yep and they have been known to soften over time too
Click to expand...

Nope. The spring rate is a constant tied to the metallurgy of the torsion bar. If you don’t heat the bar up red hot the spring rate does not change.

They do “sag” in a sense, the car will lower over time and to maintain ride height you have to turn the adjusters. That does not change the spring rate of the bar.
 
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72bluNblu said:
I honestly wouldn’t run anything less than 1” bars on anything. The original torsion bars were sized for bias ply tires. Even if you run radials in the same size as the factory tires you have more grip and need larger bars. Even when I just had 225/60/15’s on my Duster it was undersprung with 1” bars and no sway bar.

Bergman Autocraft has great choices for torsion bars. The PST 1.03’s are popular because of their pricing and they’re a good size for a street car. Firm Feel and Sway Away make good bars as well in various sizes.

All of the original bars are like 45+ years old at this point. While they may be ok, they were never intended to be in service that long. They do fail, and they can fail catastrophically. For a car that will see frequent street use I think they should be on the list of stuff that gets replaced. Firm Feel offers a reconditioning service, they shot peen and re-heat treat the origin bars. That would be useful for someone doing an OE restoration, but otherwise I’d just replace them.




Nope. The spring rate is a constant tied to the metallurgy of the torsion bar. If you don’t heat the bar up red hot the spring rate does not change.

They do “sag” in a sense, the car will lower over time and to maintain ride height you have to turn the adjusters. That does not change the spring rate of the bar.
Click to expand...

Always a voice of reason and condemning me to opening the wallet and getting yelled at more by the wife haha.
 
DentalDart said:
Always a voice of reason and condemning me to opening the wallet and getting yelled at more by the wife haha.
Click to expand...

Sorry! :D

Your plan to wait until you replace the springs is fine, although you have the bars out now.

I apologize, I’m the king of the “while I’m at it” disease.
 
72bluNblu said:
Sorry! :D

Your plan to wait until you replace the springs is fine, although you have the bars out now.

I apologize, I’m the king of the “while I’m at it” disease.
Click to expand...

I'm the same way, which is how I've ended up with disc brakes, 8 3/4 rear end, new suspension (minus torsion bars and springs), new shocks, new sway bar etc all in the last 2 months haha.
 
Never mind the numbers.Get a micrometer, clean the paint off and measure them.
maybe i missed it...what size engine is sitting in that front end.
 
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