for those who have modified their suspensions,have the stock torsion bar mounts held up to the big bars?

Here is a good thread for a rainy Saturday. I'm getting the popcorn ready cause we are getting back into the big bar vs small bar debate.

Mitch should hop in here and comment. He has been running big bars for many years and his Challenger looks way better than those cars I have seen pictures of with Magnum Force suspensions with their tires folded under the frame rail.

Mitch let me drive his car on the track and around rural roads and i have to say it rides nice. Like how you would want a handling car to ride. His car is a small block E body with some big bars and I forget how big they are at the moment.

You are I believe 1 of 1 who in over a decade has mentioned this concern, at least it is rarely brought up. It has always been odd to me the preoccupation with all the gussets, bits, welding etc added to the K member area, but all the torque/twist of whatever TB is used gets 99.9% transmitted back to the crossmember in question, and no one bats an eye to that area. A normal cage does little IMO to stiffen this crossmember where it counts. The best I can tell is 60's era nascar mopars stiffened this area with basically another crossmember upside down, and directly over the OEM crossmember, among other things. If you watch closely the Ring cuda with the 1.24-6" TB's video here, you will see my comment on if with these new larger TB's, were we seeing a lot of deflection in this area at race speed. That was ruled out by the OP.

First suggestion, unless a TB is securely pinned at one end, its spring rate is reduced, stating the obvious, and anything that increases the depth of the crossmember in this area, increases stiffness.

I can show what happens when you do the opposite (temporarily) on your car... Like 'weakening' the transmission crossmember where the T-bar anchors reside in.
(Removing the tophalf of the crossmember in the driveshaft tunnel to make room for an overdrive transmission.)

Given some time (just a few months in this case), the crossmember started to seperate itself and tear away from the floorboard sheetmetal. This happened on both sides of the transmission near the T-bar anchors.

Only after I fully welded both front and rear sides of the crossmembers to the floorboards this process was stopped.
Ofcourse the real cause, the 'missing' upper tunnelreinforcement, will be fixed to take away the strain on the floorboards.

The car, A-body Dart, has 1" torsionbars by the way.

This is true. One end of the torsion bar needs a solid foundation the other end should be the only rotational movement on the bar.

Remembering these are production cars that the factory probably didn't consider people modifying to this degree stiffening the crossmember and anchoring it solidly to the floor can't hurt a bit.

I'm sure they didn't expect the cars to last 40 plus years either. It has been discussed here about the bar sockets rusting out, breaking out, etc., but it's been awhile since there was a thread on that.

I have 1.12 bars installed and also a modified torsion crossmember from my 6 speed install. They are holding up fine but I haven't taken the car to a track yet.

I also feel that my car is undersprung compared to the race cars that were at the shop because when I grab my cage and shake the car it still wobbles a bit. When I did the same thing to an E36 M3 and a Honda CRX racecars they were both rock solid no wobbles at all. I may try my shocks on the stiffest setting to see if it makes any difference

Plan to lose weight off the front end so I will stay with the 1.12's for now

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.