torsion bar wheel rates

[Paul w]

  I am trying to find out what the wheel rate in lb's are for the MOPAR 0.96 , 1.00 and 1.25 torsion bar's, as I am going to build a race car from a 69 CHARGER.
I would like to know who to get them from  As I have spoken with firm-feel and they were great and gave me the information that they have.
The other thing I wanted to ask was is there any difference with front sway bars and if so who do you recommend that I should buy one from  As again there are more than one supplyer 

[Nacho-RT74]

we got FF specs

http://www.firmfeel.com/torsionb_b.htm

[Paul w]

Thank you NACHO, I have MOPAR Performance ones at the moment but I can not seem to find out what the wheel rate is. I am looking for 450lb or more as the car at speed is diving in to the corner way to much, due to the weight of the Big Block motor and the car I need to stop the corner of the car diving and the only way to do this is to use at least 450lb torsion bars but would like 500lb +. A pal of mine has a Big Block Ford and he has 1500lb coil springs on the front of hi Mustang and you should see that thing corner and on the road day to day it is the dogs privates The ride is sweet not harsh at all 

What sway bars do you recommend to use  they all seem to be 1"1/8 or 1"1/4  but there are a few differant one to choose from. 

[Nacho-RT74]

that rate of T bars will make a HIGHER ride height. T bars are different that coil springs. Then need to be TENSIONED to get the spring effect. for a while Coils springs are already ready to the tension by design.

I'm not an expert really on that, just talking about experience. I changed my stock ones ( what I think where .094 or so ) to 1.06. Yes it does feel stiffer, BUT if I want MORE stiff on them have to tight the bolt, and will raise the front end more than I expected. You really need a good T bar and Shock combo. A some loosen high performance T bar will act similar to a tensioned at max stock T bar. ( I said just similar, not the same ) so a good and stiff Shock will be needed to make a good stiffer combo, keeping same ride height.

For best cornering definitivelly you'll get better results with a thicker sway bar.

Anyway, Dick at Firm Feel will be a real help on advices... if you want make him a call and sure he will give you a good advice. He provides everything to Mopars suspensions

[HPP]

Mopar, Jsut Suspension, PST or anybody for that matter will have t-bar bar wheel rates that are the same as Firm Feels t-bar rates. The size determines rate, not the manufacturer so similar sizes will all rate within a percentage of each other. As such, around 400# is going to be the biggest wheel rate you are going to find in any mopar torsion bar at the 1.22 size , which is as large as you can go and still get the bar installed through the hex ends. Used to be decades ago you could repace the hex ends with 1.5' diameters as used in Grand National racing, but those days are long gone.

Also, don't get sucked in to the wheel rate vs spring rate difference your friend is feeding you. Do you know the motion ratios of your friend's Mustang? Chances are his 1500 pound spring is only exerting half or less of it actual rate because of its position on the control arm. I know chevys are around 50%, but I think Fords are even less which is why he has to go to such a large spring.

Similarly, total wheel rate is what your after so once you run out of torsion bar, you can start going bigger on sway bars or move the mounting point on the sway bar closer to the ball joint. Like above, the change in mounting point changes the motion ratio and this exerts an increase in wheel rate. You do knoe that Firm Feel offers 1.25 sway bar, right?

However, before you start just slapping big rate stuff under the nose, consider the impact it will have on the whole package. The weight distribution in your car as well as the rear spring and sway bar package needs to be considered. Those front rates may require anywhere from 120 to 225 # rear springs to avoid a massive understeer situation, but what is your front weight percentage and front to rear roll couple percentages?

Have you also considered altering the roll centers and roll moment arm? This is another way you can reduce body roll by reducing the leverage on the cars body exerted by the location of roll centers. A change in brake spindles can raise the front roll center 2-4 inches without a change in the center of gravity height which will results in a reduction in leverage the car can exert on the tire in a corner a well as providing increased spindle axis inclination and more postive dynamic caster adn additional weight jacking.

I suppose an option for bigger t-bars may be to adapt late model Ford or GM truck sockets to your mopar and have some custom bars made tn the bigger size. Of course we're talking major dollars here as most manufacturers are going to charge small fortune for custom forged bars.

[Mike DC]

IMHO the torsion bars don't have any more inherent drawbacks than coils. 

Coils are under adjustable pre-tension with their weight-jacking setups on a NASCAR.  That's the only real adjustment that you get with coils, and it's nothing fundamentally different from the adjuster bolt on a T-bar setup.  It's still just an adjustment for the spring's baseline height location either way. 




You guys can make the T-bars into granite but it may not help any. 

Is the chassis itself flexing? 
What about the tire sidewalls?
Bushings?
Swaybars adequate? 


Once you get some really huge T-bars, I doubt they will be the weakest link in the chain anymore for a while.  there's no point in throwing more stiffness at them once the flexing is elsewhere.  A Grand National mopar may need larger T-bars than the stock hexes will fit, but I REALLY doubt any of us has a geniune need for anything bigger than 1.22" on a street or mild track car. 

   

[HPP]

True, if the body is flexing and has become an active part of the suspension then you've got a lot more trouble to figure out than wheel rates. Of course I'm working from the assumption that if the original psoter is building a race car, as per the post, there will be some amount of chassis stiffening going on with connectors, torque boxes, or roll caging. But then again, we do not know any of the particulars of the class or competion rules or allowable mods. For instance. SCCA prepared class racers will use real large t-bar and s-bar rates, but are rule restricted from performing much in the way of chassis stiffening. By contrast, many local bull rings have very explicit rules about safety and stiffening of a chassis with a varying degree of allowable suspension modifications.

[Mike DC]

Yeah, the chassis issue is major.  It's probably not even a question of whether the chassis is flexing, it's only a question of where and how much. 


I just think super-stiff springs are overrated.  Of course maybe the 1960s stock factory passenger car rates are too floppy for racing, but handling is so much better served by swaybar changes in the big picture.  The four wheel springs really don't need to be stiffened much for any reason other than higher average speeds.