Moparts
230 - 260 leaf springs and 1.26" torsion bars
Posted By: docford
230 - 260 leaf springs and 1.26" torsion bars - 08/17/13 08:12 AM
Using some math from a 1971 stock car guide that factors in weight distribution and suspension type, I came up with some figures for the ideal suspension of our Hemicuda.
It would need 1.26" to 1.28" torsion bars in the front and 230# to 260# leaf springs in the rear.
MOPAR made those back in the day as I found them listed in their circuit racing parts catalog of 1973, but would you know who makes them these days ?
Posted By: Lightning
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/17/13 02:40 PM
I think Firmfeel might make the springs, but as far as the torsion bars go I'm not sure.
Posted By: TC@HP2
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/17/13 04:37 PM
Take the stock car specs with a grain of salt because they were designed for 112 and 115 inch wheelbases. Quite a bit different than your Cudas 108. Weight distribution for you will be key, especially with an elephant sitting on the nose.
No one makes 1.26 or 1.28 T-bars any more. Mopar did make 1.22 bars up until the late '90s early 00s, but they are no longer being made. You can sometimes find them on for sale forums, otherwise you may be limited to a 1.18. However, if you really have everything speced around that, talk to Dick at Firm Feel and see if they could whip up a one off set at 1.24, which, coincidently, is the biggest you can put in the factory E body sockets. To go bigger, you need to convert to C body sockets.
Also, are those rates you have calculated including sway bars at all? You want to look at total roll couple front to rear against total weight, split weight and dynamic weight, which will include sway bars and cross weight in the formula. If you are strictly looking at spring rates and then add s-bars on top of that, your balance is shot. However, since T-bars are a limiting factor, you can often manipulate balance using s-bars and leaf springs.
I'd recommend recalculating with available T-bars to back into a complimentary leaf spring number. There are limited T-bars out there, but you can spec out leaf spring rates pretty easily. Additionally, by setting up a tubular sway bar set up with modular links, you can really dial in the sway bar part of the formula using a variety of diameters and wall thicknesses to get things exactly where you want.
Posted By: Supercuda
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/17/13 04:52 PM
Not having your reference as a guide, I have to wonder if those rates are predicated on have a lot of down force at speed. I have vague recollections that on the winged cars running back then down force was a substantial factor and the spring rates took that into account. Without out that down force and that level of speed probably means you will be way over springing your ride, imo.
All that being said, it is now 2013, some 42 years later. Suspension theory and design has changed a lot. You might want to step up in time and reconsider.
Posted By: jcc
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/17/13 11:17 PM
Quote:
I have to wonder if those rates are predicated on have a lot of down force at speed. I have vague recollections that on the winged cars running back then down force was a substantial factor and the spring rates took that into account.
In 1971 stock cars, wasn't track banking a much larger factor then aero on spring rates? I never thought they achieved HIGH downforce, just a huge improvement over the huge lift demons from previous years, speaking in 1971 terms. 
Posted By: Supercuda
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/18/13 01:49 AM
I dunno, to be honest I was 6 then and I really don't recall that much about racing. I did watch it, but what 6 yo knows anything about the details.
All I know is that Chrysler put a nose cone and a wing on their race cars for aero purposes and that the cutouts/scoops atop the front fenders were supposedly there because down force would put the tire into the top of an unmodified fender.
Posted By: Viol8r
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/18/13 03:14 AM
Let's also remember what drives a lot of the aggressive set ups then and now..... grip. Most of us are not running slicks all the Way around.
Posted By: autoxcuda
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/18/13 11:29 PM
Quote:
Let's also remember what drives a lot of the aggressive set ups then and now..... grip. Most of us are not running slicks all the Way around.
I believe Docford is building a track dedicated racecar. He may be replicating the 1970 race AAR cuda that was taken to France and run with a Hemi at one point?
I thought Firm Feel makes or partially makes their own Torsion Bars. They do not make their own Leaf Springs.
There are sources for custom Torsion Bars. Sway-A-Way, Speedway Engineering. I think I asked Shroader and there equiptment would not handle the length. You've got to be able to machine stock at that lenght AND heat treat at that length. The oven at that length is the tougher of the two.
There are custom road racing leaf springs made up for the Vintage Trans Am guys. So need to find their source.
Posted By: Mattax
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/19/13 01:19 PM
Caution with respect to the Stock Car bulletin is warrented. There are several reprinted in the DC Oval Track book (P4286727) but the focus was definately circle track. In many chapters they specify "Super speedway", "Grand national" or "Short track" recommendations. The only area I can help with is the "Handling Line".
The "Neutral Line" also appears in Mike Martin's book.
(see "Suggested Reading for Handling") But it appears to be the same as the one emperically derived from short track cars (see: DC tech bulletin 141 "Basic Chassis Setup for Short Ovals). It is my conclusion that the concept is useful but the exact position of the line is not (except for the specific racing it was made for).
My conclusion is based on (a) the weights, spring rates and anti-roll numbers published for production Barracudas (A & E), and (b) my own and other mopax set ups for competition (mostly autocross). In summary, the slope is appears to be universal, but must be shifted left or right depending on the application. Details on my
Neutral Line page. I can not help as to where to get t-bars larger than 1.24, but obviously they were available for circle track at one time. (The sources listed in Martin's book were dead ends 15 years ago.) However, it is true that Firm Feel is making their torsion bars in-house.
I've never seen the tech specs on the Chrysler France race cars. The photos show a lot of body motion compared to the US trans-am prepared cars. This may be due to rules or other limitations, or the need to compete in hill climbs and other open road events where a reasonable degree of off-pavement performance and ground clearance was needed.
As far as 230# leaf springs go, that should not be too hard to find. Either of the big two circle track spring companies shpuld be able to make up a set. This may be the cheapest for testing rates and arch etc. Eaton will of course be willing to make up a more sophisticated stock type spring pack (6-7 leaf) with a primary and secondary leaf of the thicknesses, shape, for your needs and a final ratio and rate you want.
Posted By: Mopar Mitch
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/19/13 04:10 PM
I'm not certain of the exact specs, but I believe the factory-race T/A and AARs were running ~1.30 or a little larger TBs for the TransAm series (then and now with the vintage race events), as well as with the C-body anchors front and rear.
Their front sway bars are massive and tubular of the nascar-track types. Their rear sway bars are fairly small (maybe 1/2-5/8", and adjustable) and anchored low on the frame rails instead of high as we have factory-stock locations.
Their rear leafs are very stiff.. and with many leafs... I'll try to post some pics later as I have them from both cars (T/A and AAR) as seen at road race vintage events over the recent years. Their leafs are near flat at rest, and it wouldn't surprise me if their leafs are about 300-325-350 per inch. I know of SCCA C/P autocross cars that have run leafs that stiff.
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/19/13 09:13 PM
Quote:
... However, if you really have everything speced around that, talk to Dick at Firm Feel and see if they could whip up a one off set at 1.24, which, coincidently, is the biggest you can put in the factory E body sockets. To go bigger, you need to convert to C body sockets.
Also, are those rates you have calculated including sway bars at all? ...
yes, I did factor in the sway bars and converted it all to wheel rates.
Thanks for your advice. I'll get in touch with Dick Ross at FirmFeel and see if he can make me a pair of 1.24" torsion bars.
Posted By: dangina
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/20/13 02:21 PM
Quote:
yes, I did factor in the sway bars and converted it all to wheel rates.
Thanks for your advice. I'll get in touch with Dick Ross at FirmFeel and see if he can make me a pair of 1.24" torsion bars.
let us know what he says - I'm curious about this as well
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/22/13 07:40 PM
OK, I'll let you know. Right now it looks like 1.24" torsion bars without hex offset, because otherwise the car sits too high with such stiff springs.
On the rear, it should be 6 or 7 leafs to get the desired spring rate. Spring arch needs also to be factored in, as well as standars eye or reverse eye option.
Does any of you have experiences about mounting reverse eye srpings and getting rid of the necessary 2" lowering block ?
Posted By: AndyF
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/22/13 08:13 PM
Are you still using spring hangers? If so, then Firm Feel can set you up with spring hangers that have the eye bolt moved up. Then you can get rid of the axle spacers. (or reduce them)
Posted By: PHJ426
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/22/13 08:31 PM
Here are set of Mopar XHD leaf springs (both sides left springs) And a set of those rear leaf spring front mount hangars that Andy is talking about with the leaf mounted in the upper mounting hole to lower the rear of the car. There are no lowering blocks installed in the rear suspension of this car. Tires on all 4 corners here are 255/50R16.
Posted By: Mattax
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/23/13 02:48 AM
Quote:
OK, I'll let you know. Right now it looks like 1.24" torsion bars without hex offset, because otherwise the car sits too high with such stiff springs.
depends on the nose wieght, but generally I agree. 1" and even a little bigger generally can use some offset, but 1.14 up generally not needed. Again, depends on weight and assuming no other mods.
Quote:
On the rear, it should be 6 or 7 leafs to get the desired spring rate. Spring arch needs also to be factored in, as well as standars eye or reverse eye option.
Number of leafs is not the only way to skin the cat. You can pick up off the shelf circle track leaf 'mopar style' springs with 4 leafs with 200 and more lbs/in. Landrum and Afco are two well known manufactures.
Posted By: TC@HP2
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/23/13 03:51 AM
Hotchkis uses a drop eye arrangement with the front eye in their leaf spring kits.
Drop hangers can eliminate blocks too, but blocks can also be used to fine tune roll center height. Moving that front mounting point and the intersection of the eyes can have slight impacts on geometry if your trying to optimize things.
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 09/07/13 11:52 AM
Quote:
Quote:
I have to wonder if those rates are predicated on have a lot of down force at speed. I have vague recollections that on the winged cars running back then down force was a substantial factor and the spring rates took that into account.
In 1971 stock cars, wasn't track banking a much larger factor then aero on spring rates? I never thought they achieved HIGH downforce, just a huge improvement over the huge lift demons from previous years, speaking in 1971 terms.
That is correct. I do have some downforce and drag numbers from the Chrysler wind tunnel of 1970. It loks like the engineers where much more focused on optimizing drag than tuning in more downforce back then.
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 09/07/13 11:59 AM
Quote:
Hotchkis uses a drop eye arrangement with the front eye in their leaf spring kits.
Drop hangers can eliminate blocks too, but blocks can also be used to fine tune roll center height. Moving that front mounting point and the intersection of the eyes can have slight impacts on geometry if your trying to optimize things.
Good point ! We do have two monting positions on our front leaf spring hanger and four on the rear.
I'm not really a fan of reverse eye springs on a racecar, as the leaf is the "pulling" on the eyes and not "resting" on the weight of the car.
However, here is an interesting picture of the leaf springs on Richard Petty's 1968 Roadrunner.
Posted By: Mopar Mitch
Re: 230 - 260 leaf springs and 1.26" torsion bars - 09/07/13 04:39 PM
One additional concern should be, if the front spring eye location is changed up/down then to use angle shims at the leaf/differential to re-adjust the drive shaft / pinion angle.
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 09/08/13 11:03 AM
Quote:
One additional concern should be, if the front spring eye location is changed up/down then to use angle shims at the leaf/differential to re-adjust the drive shaft / pinion angle.
Good point! What pinion angle would you dial in on a roadracing HEMI car ?
We used -4° in drag racing, but that might be a lot for the road circuit
Posted By: Mopar Mitch
Re: 230 - 260 leaf springs and 1.26" torsion bars - 09/09/13 02:56 PM
Docford -- I'm uncertain what to advise for the pinion angle for the car you describe. I believe the Mopar Performance Chassis book, etc, advise how to do this.... you'll probably need an angle gage. (I had a racer-pro (Jim McKamey) do mine as I was also having the entire suspension balanced... back in the mid-80s.)
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 11/24/13 11:03 PM
Torsion bars and leaf spring came in this week. They were custom made by FirmFeel
Posted By: jcc
Re: 230 - 260 leaf springs and 1.26" torsion bars - 11/25/13 12:58 AM
Posted By: brads70
Re: 230 - 260 leaf springs and 1.26" torsion bars - 11/25/13 07:36 PM
Quote:
Torsion bars and leaf spring came in this week. They were custom made by FirmFeel
Post up some pictures please! 
Posted By: Mopar Mitch
Re: 230 - 260 leaf springs and 1.26" torsion bars - 11/25/13 10:59 PM
What were the final specs on the TBs and leafs? This is for a hemi-Cuda? Which body.. E or A? Which gen-Hemi?
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 12/22/13 11:52 AM
Quote:
What were the final specs on the TBs and leafs? This is for a hemi-Cuda? Which body.. E or A? Which gen-Hemi?
1.24" torsion bars
1.25" frt sway bar
230# leaf springs
0.75 rear sway bar
1970 Cuda with 426 HEMI
3780# w driver and half tank of gas
weight bias 54% frt 46% rear
complet car can be seen here http://www.hemicuda-france.com
Posted By: autoxcuda
Re: 230 - 260 leaf springs and 1.26" torsion bars - 12/22/13 12:17 PM
Quote:
Quote:
What were the final specs on the TBs and leafs? This is for a hemi-Cuda? Which body.. E or A? Which gen-Hemi?
1.24" torsion bars
1.25" frt sway bar
230# leaf springs
0.75 rear sway bar
1970 Cuda with 426 HEMI
3780# w driver and half tank of gas
weight bias 54% frt 46% rear
complet car can be seen here http://www.hemicuda-france.com
I assume those T-bars were made on the factory A/B/E-body 1.25" front and rear hex?
Are those T-bars factory E/B body length?
I think comparing to a late 60's to mid 70's Nascar cup car chassis it out the window. Those T-bars are a different length AND the lower control arms are a different length too. So the calcs to get the wheel rates are a different animal than your stock E/B body LCA and T-bar length. I also would not assume the '70 Trans Am cars uses stock length T-bars and LCA's. Not saying they didn't, but I would want a measurement confirmation.
IMHO, a 230 lbs rear spring on a road course seem like a lot for 1.24" dia E/B-body length torsion bars. But, what was Dick Ross's recomendation/advice?
It looks like you have been racing this same car for the past 3 years? What springs were in it then?
Was there a problem with that spring package?
Posted By: Mopar Mitch
Re: 230 - 260 leaf springs and 1.26" torsion bars - 12/23/13 07:42 AM
On my T/A, I run the 1.24 TBs and 225 pound/inch with 5" free arch rear leafs (fiberglass mono-leafs from FlexaForm)... compressed to about 1.5" remaining arch,... and have 1.25" solid fron sway bar, 1.0" solid rear sway bar, Red re-valved Konis front/rear... car handles great, very neutral; weight is ~3150 w/o driver and with ~1/8 tank of gas (52% front, 48% rear)... this data is when the car is setup for national SCCA E/SP competition. even on the hi-speed road courses it handles great.. still relatively neutral.
I think the weight% with the 426 Hemi up front is going to be greater than what is indicated...??? I'd use a 1.0" rear sway bar to help offset the front weight.
Posted By: TC@HP2
Re: 230 - 260 leaf springs and 1.26" torsion bars - 12/23/13 04:43 PM
The more you move weight rearward, the higher your rear rates need to go to balance things out. With a 54% front bias WITH an elephant up front, more leaf rate is probably required. I would have guess a Hemi equipped car to be more like 58-60% front weight, so the change to 54% is a significant change.
Posted By: Mopar Mitch
Re: 230 - 260 leaf springs and 1.26" torsion bars - 12/23/13 09:52 PM
Best bet would be removing weight from the car.. that 426 hemi is very heavy. It'd be interesting to see the actual weigh scale results, each respective corner.
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 02/02/14 11:11 PM
Quote:
Best bet would be removing weight from the car.. that 426 hemi is very heavy. It'd be interesting to see the actual weigh scale results, each respective corner.
Weight with half a tank of gas and driver is 3,780 lbs
Front/Rear bias is 54/46
Left/Right bias is 52/48
We are now moving the fuel and dry sump tank to get 50/50 left to right weight bias. We are also removing about 40 lbs by doing that, thanks to shorter routing of the -16 oil hoses and thus, carrying less oil in the dry sump circuit
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/17/14 10:05 AM
The new springs worked wonders on the Nurburgring, as we were able tonshave a full 26 seconds of our best lap time from 2012. Lapping the 14 mile roadcourse in 8.52 made us a Porsche Terror !!
Here is the onboard video
http://www.hemicuda-france.com/2014/08/onboard-the-hemicuda-around-the-nordschleife.html 
Posted By: feets
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/17/14 02:35 PM
Very nice!
It begs the question of what time could it turn on a dry track with more cooperative traffic?
Posted By: RylisPro
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/17/14 06:00 PM
That car is awesome! Man you got big balls running hard in the rain! Nice save too! Last time I was in the wet my car spun and had a fender bender.
Your car moves pretty good despite the weight. The leafs and t-bars must be heavy but really make a difference!
Posted By: 72Swinger
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/17/14 07:02 PM
I've really been kicking around the splined front swaybar idea. Basing it from my existing Hotchkis mounts, it really would'nt be to much of a stretch.
Posted By: jcc
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/17/14 11:22 PM
I assume what I am asking about is just a video or mounting visual distortion artifact, but does it look like the trans tunnel area/rear TB mounting crossmember flops around a lot based on bumps and/or cornering? Nothing else inside the car seems to move much, relative to camera, but this area. If so wow, if not nevermind.
Posted By: ntstlgl1970
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/18/14 06:47 AM
that was a really cool video
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/18/14 08:57 AM
Quote:
That car is awesome! Man you got big balls running hard in the rain! Nice save too! Last time I was in the wet my car spun and had a fender bender.
Your car moves pretty good despite the weight. The leafs and t-bars must be heavy but really make a difference!
Thanks 
yes , the Cuda now is really fun to drive and one could even let his mom cruise it on the street
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/18/14 08:59 AM
Interesting observation! I'll take a second look at the video
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/18/14 09:13 AM
Quote:
I assume what I am asking about is just a video or mounting visual distortion artifact, but does it look like the trans tunnel area/rear TB mounting crossmember flops around a lot based on bumps and/or cornering? Nothing else inside the car seems to move much, relative to camera, but this area. If so wow, if not nevermind.
yes, it is an optical distortion due to the camera moving under braking and acceleration. If you look closely, you'll see the top bar of the rollcage move the same. You got sharp eyes, though 
Posted By: Mattax
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/19/14 04:44 AM
Nice Job. Video looks great. Most important is it turned out the way you wanted and that it is a joy to drive.
Posted By: AlexP
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/19/14 06:57 PM
Amazing..
What is the wheel and tire set up?
Posted By: HUSTLESTUFF
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/22/14 02:23 PM
Why are you selling it? Dang just when its fast!!!Building another?
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/30/14 09:24 AM
Quote:
Amazing..
What is the wheel and tire set up?
We're running NASCAR 10x15 inch wheels with AVON CR6ZZ vintage racing tyres
http://www.longstonetyres.co.uk/page/avon-cr6zz
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/30/14 09:27 AM
Quote:
Why are you selling it? Dang just when its fast!!!Building another?
Well, all good things come to an end. I had to make a choice between the Charger and the Cuda, due to $$$ reason
Posted By: docford
Re: 230 - 260 leaf springs and 1.26" torsion bars - 08/31/14 01:59 PM
Thanks to a fellow enthousiast, I got the original broadcast sheet of the car. It rolled off the Hamtrack assembly line as a 383-4 barrel 4 speed Barracuda. Is there a way to tell the torsion bar size and spring rate that is came with originally ?
Here is a link to a pdf of that broadcast sheet:
http://www.hemicuda-france.com/2010/08/our-barracudas-broadcast-sheet.html
Posted By: Mattax
Re: 230 - 260 leaf springs and 1.26" torsion bars - 09/01/14 04:23 AM
Quote:
Thanks to a fellow enthousiast, I got the original broadcast sheet of the car. It rolled off the Hamtrack assembly line as a 383-4 barrel 4 speed Barracuda. Is there a way to tell the torsion bar size and spring rate that is came with originally ?
Probably Yes. The first entries on line five are the codes for the t-bar, followed by the rear springs.
Somewhere, someone like Barry Washington knows how these numbers relate to part numbers. Try cross posting under "restoration".
- Matt
Posted By: RichV
Re: 230 - 260 leaf springs and 1.26" torsion bars - 09/16/14 02:52 AM
C body torsion bar sockets transplanted into the crossmember and lower control arms will allow you to further increase your front spring rate. The Trans AM cars did this, but they did have to reinforce their torsion bar crossmember.