Torsion bars and rear springs

[Ronald Weishaar]

I have a 65 Coronet 440 that when finished will have a 440 engine with A/A's Max Wedge set up and exhaust manifolds in front of a 4 speed. Originally had a 273 auto. I'm asking what would be the proper torsion bars and rear springs for this set up? Intended for a nice cruiser with a little heavy foot at times. Thanks

 

[VANDAN]

I'm doing my '63 330 with the same set up, but a 727 TF. That weight up front is an anchor, so I used the MP .960 bars up front, and a set of HD rear springs from ESPO. It's also frame tied with U.S.Car Tool frame ties, so that should stiffen it up some. It's not rolling yet, so I can't comment on the results...

 

[66Satellite47]

IMHO the .960 Mopar T-Bars or equivalent would be good, the rear springs are a little different due to the one year only 21" front segment leaf springs. I used a stock Super Trak Pak spring set on the stock '65 main leaf. This setup worked fantastic. If Espo or Eaton Spring Detroit? can duplicate that, you'd be happy.

 

[PRND21]

.960 bars on my 65 Belvedere, I’m happy.

 

[ckessel]

I have the 1.06 bars and XHD springs for my 65 500. I'm setting the car up to autocross and do track events mostly. Plus fun curvy road stuff. Car has been on hold for almost 3 years because we moved and I'm in the process of getting a 2nd garage built to work on it in.

 

[Ronald Weishaar]

.960 bars on my 65 Belvedere, I’m happy.

Was going to go with MP .960 T bars but it seems as they and the .920 bars are and have been on back order for months.

 

[Ronald Weishaar]

Was going to go with MP .960 T bars but it seems as they and the .920 bars are and have been on back order for months.

I have found a set of P5249157 (.920) in Calif but the cost without shipping is close to $400. P-S-T has t-bars spec 1.030 for $249.00 just alittle heavier than the .960. Do you all think this will be ok or to much?

 

[Nate S]

Did this to my '64 Sport Fury last summer. .92 bars up front, '70 'Cuda 440/426 leafs in the rear. Mancini makes a mount for the 'Cuda springs in an early B-body but they sit a little low (have a set if you want them). I took the original mounts and re-drilled as far forward as I could and not have the spring rub the studs. Stretched the wheelbase an un-noticeable .19" but sits at original height. Rides great this way.

 

[66Satellite47]

I have found a set of P5249157 (.920) in Calif but the cost without shipping is close to $400. P-S-T has t-bars spec 1.030 for $249.00 just alittle heavier than the .960. Do you all think this will be ok or to much?

The diameter is not the key factor, a .960 bar may actually be about the same as .960 bar. The actual spring rate is the variable. Just say'in.
OOpps, meant .960 may be same as 1.03 bar.

 

[33 IMP]

I'm pretty sure that a 1.0" bar is more than 10%stiffer than a .9"bar . I'll bet @RJRENTON knows the math. (My guess is that a 1.03 bar is at least half again as stiff as a .920)

 

[RJRENTON]

At your request...
Torsion spring torque is calculated the same way you calculate a working load. To calculate the torque of a torsional spring you must divide the spring rate by the amount of degrees of deflection your spring will be required to travel.
is a constant with units of newton-meters / radian, variously called the spring's torsion coefficient, torsion elastic modulus, rate, or just spring constant, equal to the change in torque required to twist the spring through an angle of 1 radian. It is analogous to the spring constant of a linear spring.
Question: ■Derive The Torsional Spring Constant For The Rod Under Torsion, T = K@t Find K). Given Data: T (torque), C (cross-section Radius), L (length Of Bar), G (shear Modulus) Front View

Short answer.....the diameter of the bar plus how many degrees of rotation are the major factors. Since the diameter of the bar is increased, yes, the bar will be more resistsnt to twist but in order to accurately compare the two examples, one must figure the spring rate of the first bar then factor the percentage of the increase in two examples...spring rate is a linear relationship ..... the increase in area results in an increase in the spring constant assuming the identical degrees of rotation. Hopefully this answers you question.
BOB RENTON

 

[Ronald Weishaar]

At your request...
Torsion spring torque is calculated the same way you calculate a working load. To calculate the torque of a torsional spring you must divide the spring rate by the amount of degrees of deflection your spring will be required to travel.
is a constant with units of newton-meters / radian, variously called the spring's torsion coefficient, torsion elastic modulus, rate, or just spring constant, equal to the change in torque required to twist the spring through an angle of 1 radian. It is analogous to the spring constant of a linear spring.
Question: ■Derive The Torsional Spring Constant For The Rod Under Torsion, T = K@t Find K). Given Data: T (torque), C (cross-section Radius), L (length Of Bar), G (shear Modulus) Front View
View attachment 944478
Short answer.....the diameter of the bar plus how many degrees of rotation are the major factors. Since the diameter of the bar is increased, yes, the bar will be more resistsnt to twist but in order to accurately compare the two examples, one must figure the spring rate of the first bar then factor the percentage of the increase in two examples...spring rate is a linear relationship ..... the increase in area results in an increase in the spring constant assuming the identical degrees of rotation. Hopefully this answers you question.
BOB RENTON

Think you, I think!

 

[66Satellite47]

RJ, in your formula is the shear modulus a function of the steel alloy & temper? It appears this math presumes the steel is the same for any different cross sectional area.

 

[RJRENTON]

RJ, in your formula is the shear modulus a function of the steel alloy & temper? It appears this math presumes the steel is the same for any different cross sectional area.

I assumed the shear modulus is a constant with regard to the alloy and temper, not exactly knowing those variables. As this question delt with a larger x-section and not knowing the degrees of deflection the bar was subjected to, I made those assumptions....perhaps taking a few liberties....? Maybe akin to the selection of valve springs....wire diameter, alloy, number of active coils, free length, spring constant, installed height, compressed height.....change one variable and the overall characteristics change.....? Just a thought....
BOB RENTON
BOB RENTON

 

[HEMI-ITIS]

You guys should really look into double adjustable shocks!!
The control factor is fantastic!

 

[66Satellite47]

I assumed the shear modulus is a constant with regard to the alloy and temper, not exactly knowing those variables. As this question delt with a larger x-section and not knowing the degrees of deflection the bar was subjected to, I made those assumptions....perhaps taking a few liberties....? Maybe akin to the selection of valve springs....wire diameter, alloy, number of active coils, free length, spring constant, installed height, compressed height.....change one variable and the overall characteristics change.....? Just a thought....
BOB RENTON
BOB RENTON

Bob, that's why I said the bar size is not the only thing to consider, especially comparing Mopar T bars to aftermarket.

 

[hunt2elk]

I have found a set of P5249157 (.920) in Calif but the cost without shipping is close to $400. P-S-T has t-bars spec 1.030 for $249.00 just alittle heavier than the .960. Do you all think this will be ok or to much?

I really like the PST 1.03's. Have them on 2 of my cars. Can't beat them for the price imo.