torsion bar cross member

Another area that subframe connectors help. I have a hand made upper cross member to facilitate the T56. I am confident that I can go hog wild on torsion bar size if I want.

I've had 1.120" torsion bars in for a few years now with no issues.

I cut the entire top "hump" section off of my crossmember to fit my trans and rebuilt it with some 1/8" plate. 1.06 t-bars with a 440. been ok so far. I might want to go up to 1.12. The thing I wonder about is how much t-bar you can run without a cage/where the spring rate exceeds the chassis stiffness.

"exceed" is subjective, its all a system, like having 6 or more springs in series, they all interact, no single one controls the result.

Edit: unless one has the perfectly stiff chassis but whatever means, the chassis is one of the the 6 "springs", and there are likely other "springs" in parallel, like a 5oo?lb motor on rubber motor mounts, to further complicate the matter

Metal fatigue would be more correct to mention here me thinks.
Enough and smart reinforcing will counter/pospone metal fatigue in a chassis.

Just read all the comments. My 1.24 TBs are the largest that fit within the factory 1.25 hex opening (E bodies, and I believe all a and B bodies, as well. I believe the huge C-bodies have larger hex openings... ~1.4 or larger?

The factory race-prepped T/A/AAR TransAm cars run ~1.46 TBs... those are similar to old time NASCAR TBs... running the C-body hex openings.

Too bad MaMopar was wimpy with the soft and small ~0.94 TBs for their T/A and AAR street cars... they should've stepped up to at least ~1.12 for those cars to compliment the handling. I progressively tried different size TBs, setting up the car for national level competition SCCA E/SP class solo/autocross racing during the 80s and found the softer TBs (below the utlimate 1.24 diameter) allowed far too much lift and dive under hard driving. Those multiple choice size TBs were then available from a company called California Moparts/Suspension.. ahead of their times back then. At the same times, I would make other respective changes to the leafs and shocks. My sway bars were custom-made of solid steel 1.25 front, 1.0 rear. My overall combination works great for me... and the results have proved it in competition winning or placing high in many events and championship season series (only the nut-behind-the-wheel determines the final day's results and can always use improvement).

Anyone who is "afraid" that, for an E or B body, the 1.24 TBs are too stiff for the street, or for racing, you should experience it first before you comment. I offer you advice from my experience... and its still based upon an "overall" package.

Remember, too, that my car was setup to be running primarily on smooth surfaces, without much road bumps, etc. How is it on the street/highway?... Streets.. naturally, avoid pot-holes and slow down for railroad tracks; Highway?... typical smooth roads.. fantastic!

The hex openings on my Challenger have never failed with all the different TBs I'v tried... the 1.24s have been in the car since ~1987. Further, as per my class rules that I have the car setup for (SCCA E/SP solo/autocross and a couple other related club/class rules), I couldn't legally run any hex setup larger than the factory 1.25 openings.

If you'd want to add welding re-inforcement around the hexes, that would give you some added peace of mind... I believe the factory-prepped T/A and AAR TransAm cars had welded reinforcements at those hexes, as well as everywhere else on the car (same for any NASCAR vehicle, etc). Fortunately my car is 99.9% rust free and no cracks anywhere, etc.

As a final note, my good racing friends -- the Sandberg family -- have also run the 1.24 TBs on their various E-bodies... A-OK street/hwy/or racing.... highly recommended! I know Firm Feel will make these TBs and they may already have some sitting aside from a recent production (or 1.22 diameter which is also a very good TB size).

Project Black n blue-the 70 charger R/T received frame ties and boxing in for the torsion bar x member and other places underneath. I hid most of the mods under a layer of spray-on bedliner. The car rides like the family sedan yet cuts a great corner

The definitive proof that the t bar area requires reinforcement was the numerous comments from the driving school instructors whom were quite amazed at the flat handling of the big fat car.

This is with .98 t bars and hemi leaf springs...

A properly reinforced car does not need a ton of rate in the t bars or rear springs to handle properly.

I picked up some of the reinforcing t-bar caps from ART. I plan on punching out a bunch of extra holes in them so that I can plug weld them to the existing stucture plus the usual lap welds. Seeing the tears on the floorpan from above makes me think about some extra attatchments there too. Maybe some more plug welds. My Rotabroach units will get a good workout.

http://www.autorust.com/

Maybe it is because my car has a full cage that it feels that way? I'm pretty sure that most street driven Mopars don't and have way more chassis flex than mine. I can jack up the front passenger side and the rear lifts higher than before having the cage installed. I am going to keep the 1.12's for now, nothing wrong with them. Planning to lose more front end weight to see if that makes an overall improvement.