Torsion bars for better handling; your experience?

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Hemi Denny! as a Kart racer for about thirty years( I do not know about a "cart")yes they do have suspension. It is in the chassis design. Manufacturers go to great lenghts designing different chassis designs to achieve different caracteristics with euro teams turning up with over a dozen different chassis to test at a race meeting. Rear axles hubs wheel designs, front stub axles and front hub designs all play apart in the level of handling as a Kart needs to release off a corner which gives a speed advantage down the straight. Now if you think a Kart has no suspension so it is easy to tune think again.

when I grew up (60s), we called them go-carts, not Karts....my bad on that one.

What I mean by suspension is torsion bars / coil overs / shocks. I realize (more modern) Karts have camber / caster adjustment just like our cars do. Most have track width and wheelbase adjustments too. But rarely, if ever (???) have I came across a Kart with torsion bars or coil-overs....NEVER in my day (60s). A move up to a Quarter Midget is when I see any kind of suspension. IMO, the SIMPLE fact that they (the Kart) run on a fairly smooth (no big bumps) track , are inches from the ground, have wide low profile tires, virtually NO body roll (predictable) is why they haul *** when cornering.

My question was...and only a question to those that AutoX ...is why not try to replicate? I asked because I do not Autocross, but never afraid to ask...what if?... or why not? ....to those that do.
 
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Thanks for the reply.......looks like shocks (if they came with them as our Mopars did) are required....so much for the go-cart suspension.

soooo.....you run the shocks as soft as you can get away with, but utilize anti-roll bar to control the body roll?....sounds like my favorite street set up


In general, the goal is to run the softest suspension that will work well. The math for the physics and engineering is in Carrol Smith's Tune to Win but I think that sums it up. The better traction of tires in general has upped the roll rates and therefore the resistance needed.


sorry...I should have said ...suspension, not shocks. and was only guessing with a soft suspension, it is necessary to control the body roll with a big anti-roll bar.

for Autocross....what are the basics for tuning the shocks? I appreciate your input.
 
on my duster which is bb and t56, I have 1" bars, hellwig tube sway bar, moog offset upper bushings, reinforced upper shock mounts, stiffner plates on the lower control arms, expo 6 leaf with delrin front eye bushings, hotchkis Fox shocks. Cordoba front brakes and explorer disc 8.8 rear. 17s. I used to have the kyb shocks, I noticed a difference, but not a big enough difference to justify those shocks as an upgrade, for the cost. I also have problem with the upper shock bushing on the hotchkis shocks, the bushings shear off i wind up finding what looks like a calamari ring somewhere in the engine compartment and what's left of the bushing will fit inside the hole. I've been told that is common with that style upper shock mount. I also wonder if brand of tb has any effect, this car handles great but rides stiff. It honestly gets old sometimes. If coarse we don't have the nicest roads here in nj.

Ride quality is subjective, but if you have a big block, only 1" bars and Hotchkis shocks you shouldn't have a stiff ride. I'm guessing your car is lowered too far for the 1" torsion bars and you're bottoming the suspension out. Hotchkis shocks vs KYB's are a night and day kind of difference, I've done it. Unless you're bottoming the suspension, in which case it will still be a harsh ride because you're slamming parts together.

When I had 1" bars in my small block Duster I couldn't lower it that much to keep it from bottoming out and the ride was still pretty soft. Which is why I went up to 1.12" bars.

when I grew up (60s), we called them go-carts, not Karts....my bad on that one.

What I mean by suspension is torsion bars / coil overs / shocks. I realize (more modern) Karts have camber / caster adjustment just like our cars do. Most have track width and wheelbase adjustments too. But rarely, if ever (???) have I came across a Kart with torsion bars or coil-overs....NEVER in my day (60s). A move up to a Quarter Midget is when I see any kind of suspension. IMO, the SIMPLE fact that they (the Kart) run on a fairly smooth (no big bumps) track , are inches from the ground, have wide low profile tires, virtually NO body roll (predictable) is why they haul *** when cornering.

My question was...and only a question to those that AutoX ...is why not try to replicate? I asked because I do not Autocross, but never afraid to ask...what if?... or why not? ....to those that do.

sorry...I should have said ...suspension, not shocks. and was only guessing with a soft suspension, it is necessary to control the body roll with a big anti-roll bar.

for Autocross....what are the basics for tuning the shocks? I appreciate your input.

Denny I'm honestly surprised by your questions given your background in designing suspension.

Tuning a car for AutoX isn't really that different from tuning suspension for anything else. The goal is to maintain the contact patch on the ground with the amount of suspension travel you have with your vehicle or the amount of travel you need to create for the terrain. Shocks should be critically damped for ideal performance regardless of what you're doing, road racing or trophy cup offroad. They need to be well matched to the spring rates no matter what type of racing you do.

AutoX courses are usually set up in parking lots, not on race tracks. So the surfaces vary quite a bit, they can actually be pretty rough. And regardless, because they're usually fairly short tracks with slow corners you're usually hard on the gas or hard on the brakes to get the best time, so there's a lot of acceleration and dive. That alone requires suspension travel to maintain traction. I'm no expert AutoX'er, but the tracks I've driven have all been rough enough that a car without suspension travel wouldn't have been ideal to keep your tires planted or the handling consistent. I've been on tracks with my Austin Healey that it was quite a bit too stiff for, it was set up for vintage racing and very soft tires and with street tires on AutoX tracks it was usually well into oversteer mode.

Lowering the cars definitely helps with the CG, and then if you can't modify the suspension points you up the wheel rate to keep the suspension from bottoming out. Based on the class you run the softest tires you can, and that in itself requires a higher wheel rate because you put more force through the suspension.

Then as Mattax said it's just a matter of maximizing your tire contact, which generally means the softest suspension you can get away with. That's relative because with these cars you're talking about 4 or 5" of suspension travel. Even stock that's pretty true. On my car, lowered as it is, I still have a pretty similar travel range to stock because of the way I've shortened and adjusted the bump stops to add travel back into the system.
 
Nicely stated.

I'll just add that any time weight is transfered in corner its going to decrease the available traction.
Anyone interested in more should check out any one of the well regarded books on the subject such as Carrol Smith mentioned before, Fred Puhn's Handling, or Herb Adam's Chassis Engineering.
I used this picture of the MG because its an extreme example of taking the wieght off the inside front.
midget-lift-ripken_062605_1147-sized-jpg.jpg

It always hurts, even when its necessary.
The was a great article in Circle Track (Feb, 2009) where Herb Adams did just this sort of modification (including adding a sway bar and reducing compliance) with lap times on an asphalt track.

Then as Mattax said it's just a matter of maximizing your tire contact, which generally means the softest suspension you can get away with. That's relative
You can say that again! Definately not soft by typical standards especially more so when running R comps, slicks or A compounds.
 
Yeah I guess everything can be subjective.
It’s possible the suspension has bottomed out a couple times but it is definitely not too low. I have full length headers on the car they would be scraping everywhere.
Ride is nice on the highway. Handles great around turns. Potholes and rr tracks things like that, get old when I drive the car a lot. I’m just giving my experience with this car. It transformed from a stock slant. I think I liked the ride the most with the 920 bars sway bar and kyb. I’ve had it set up like this about 10 years and have daily driven it, cruised it all over the place, Up and down the east coast.
 
I was asking about shock tuning..... simply what the car is doing to to make you want to soften or stiffen the compression / rebound of the shock. I was hoping the guys with the experience could give some simple guidelines.

Maybe it is just common sense like...
if the front is diving too much on breaking....add some compression (front)
if I want more rear traction (transferring the weight) .........remove some of the rebound (front)...keep the rear compression soft

It is a given regarding the need to maintain maximum tire contact, the question was HOW thru shock tuning.

BTW...I still like my go-cart / strut set-up....years ago when we ran dirt flat track with 3 and later 4-wheelers, the guys with any suspension were slow......but maybe that was more like drifting cause we slid thru the corners while the guys with suspensions were busy trying to keep their tires on the ground and not bicycling.


sorry....didn't mean to hi-jack the thread.....back to your discussion on torsion bars and handling.
 
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Was going for handling/comfort on my 75 Duster 318. .890 t-bars, heavy sway bar, kyb gas-adjust shocks, new rubber bushings. This thing is a peach to drive and handles great for normal driving. Get decent tires and align it to modern specs (basically opposite of bias-ply 1970s specs).
Update: I later switched to 1.03" torsion bars and I like them better. It feels more nimble and handles bumps like a champ. I now find myself looking for sharp turns and bumps to go over for fun. Go heavy sway bar and heavy torsion bars, and then quality shocks to soften the ride imho. I have yet to finish this project, because I haven't had time and enjoy driving it as-is, but I think I'm going to be very happy when I install my fully adjustable UCA's and some Bilstein shocks.
 
Glad this got bumped, because I need it. The guy that built my Duster was a pretty good wrench...but a Chevy guy and totally unfamiliar with Mopars. As such, he made some...interesting...part selections. I'm 99% sure I have a JS front swaybar, with probably-original .85" bars on the otherwise-totally-rebuilt (PST) front end. (Car is a factory 318.) He coupled this with Super Stock rear springs, too-short underride traction bars, and HD shocks...with the result the front is way soft, and the rear is like a hardtail Harley. :BangHead: Obviously, most of this has to be dealt with.

Though a big-bumper car, my Duster is relatively light (~3300), with a 4-speed and no power options. I was thinking .99" bars (184lb), but this thread has me thinking I might want the 1.04" or even 1.09" MP bars.

Also, I dug up the old tech article about wheel rates from Mopar Action. For 35.8" A-body bars, the rates are...

.81 (MP drag)-82
.83 (slant)-92
.85 (315)-101 (No wonder mine handles like a marshmallow.)
.87 (340)-109
.89 (B/RB)-120
.92 (MP HD)-137
.94 (76 police)-149
.99 (MP)-184
1.04 (MP "HD solo")-224
1.09 (MP circle track)-270
1.14 (MP circle track)-323(!)
 
Nicely stated.

I'll just add that any time weight is transfered in corner its going to decrease the available traction.
Anyone interested in more should check out any one of the well regarded books on the subject such as Carrol Smith mentioned before, Fred Puhn's Handling, or Herb Adam's Chassis Engineering.
I used this picture of the MG because its an extreme example of taking the wieght off the inside front.
View attachment 1715244766
It always hurts, even when its necessary.
The was a great article in Circle Track (Feb, 2009) where Herb Adams did just this sort of modification (including adding a sway bar and reducing compliance) with lap times on an asphalt track.


You can say that again! Definately not soft by typical standards especially more so when running R comps, slicks or A compounds.

Clean little Midget there!
 
Glad this got bumped, because I need it. The guy that built my Duster was a pretty good wrench...but a Chevy guy and totally unfamiliar with Mopars. As such, he made some...interesting...part selections. I'm 99% sure I have a JS front swaybar, with probably-original .85" bars on the otherwise-totally-rebuilt (PST) front end. (Car is a factory 318.) He coupled this with Super Stock rear springs, too-short underride traction bars, and HD shocks...with the result the front is way soft, and the rear is like a hardtail Harley. :BangHead: Obviously, most of this has to be dealt with.

Though a big-bumper car, my Duster is relatively light (~3300), with a 4-speed and no power options. I was thinking .99" bars (184lb), but this thread has me thinking I might want the 1.04" or even 1.09" MP bars.

Also, I dug up the old tech article about wheel rates from Mopar Action. For 35.8" A-body bars, the rates are...

.81 (MP drag)-82
.83 (slant)-92
.85 (315)-101 (No wonder mine handles like a marshmallow.)
.87 (340)-109
.89 (B/RB)-120
.92 (MP HD)-137
.94 (76 police)-149
.99 (MP)-184
1.04 (MP "HD solo")-224
1.09 (MP circle track)-270
1.14 (MP circle track)-323(!)

And since I don't know how to do multi-quotes in one post, here you go.


1670199518867.png
 
1" bars and a good set of sway bars does wonders for these cars. Its a night and day difference.
 
1" bars and a good set of sway bars does wonders for these cars. Its a night and day difference.

Night and day difference vs stock, but still leaves a lot of room for improvement in the handling department. Still isn’t enough with wide, modern performance tires.
 
And since I don't know how to do multi-quotes in one post, here you go.

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View attachment 1716018394
First: click the "+QUOTE" button at the bottom right. When you have selected all the quotes, click the "Insert Quotes" button under the text box. The quotes will pop up, click the "Insert" button on the bottom right and they go in the text box.

I saw PST 1.03" (230lb) bars...anything wrong with those? Looks like they're on sale.

Night and day difference vs stock, but still leaves a lot of room for improvement in the handling department. Still isn’t enough with wide, modern performance tires.

Which I also plan on.
 
First: click the "+QUOTE" button at the bottom right. When you have selected all the quotes, click the "Insert Quotes" button under the text box. The quotes will pop up, click the "Insert" button on the bottom right and they go in the text box.

I saw PST 1.03" (230lb) bars...anything wrong with those? Looks like they're on sale.



Which I also plan on.

Nothing wrong with the PST 1.03” bars. Quite a few people here run them, they’re a great update for more modern handling without going full canyon carver or autoX.
 
I have PST 1.03 bars, Bilstein RCD shocks all around and Mancini heavy duty leaf springs with 1" lowering blocks, the front is lowered too. 1970 340 Dart. I don't do much high speed cornering but the Dart handles great. Next on the list will be a Borgeson or Firm Feel steering box and bigger sway bar. It's night and day compared to stock.
 
Glad this got bumped, because I need it. The guy that built my Duster was a pretty good wrench...but a Chevy guy and totally unfamiliar with Mopars. As such, he made some...interesting...part selections. I'm 99% sure I have a JS front swaybar, with probably-original .85" bars on the otherwise-totally-rebuilt (PST) front end. (Car is a factory 318.) He coupled this with Super Stock rear springs, too-short underride traction bars, and HD shocks...with the result the front is way soft, and the rear is like a hardtail Harley. :BangHead: Obviously, most of this has to be dealt with.

Though a big-bumper car, my Duster is relatively light (~3300), with a 4-speed and no power options. I was thinking .99" bars (184lb), but this thread has me thinking I might want the 1.04" or even 1.09" MP bars.

Also, I dug up the old tech article about wheel rates from Mopar Action. For 35.8" A-body bars, the rates are...

.81 (MP drag)-82
.83 (slant)-92
.85 (315)-101 (No wonder mine handles like a marshmallow.)
.87 (340)-109
.89 (B/RB)-120
.92 (MP HD)-137
.94 (76 police)-149
.99 (MP)-184
1.04 (MP "HD solo")-224
1.09 (MP circle track)-270
1.14 (MP circle track)-323(!)
Feeling like a marshmallow can have as much or more to do with the shocks than the springs.
The SS springs - and the raised raised rear can make the back end feel stiff and jumpy.
The combination of softer front and SS springs when done right can provide excellent weight transfer to the rear when using race tires.
On the other hand as you observe, its a poor combination for turns and lane changes on the street and track.

The front to rear roll rates effect on handling relate most directly to front rear weight balance.
How high the spring rate ought to be will depend on the useage. Generally speaking, the worse the traction and rougher the surfaces, the softer rates will be more effective in maintaining the obtainable contact and traction. Tire choice, surface conditions, and use should drive the other decisions. The stickier the tire, the more rate will be wanted - not only for geometry and physics reasons, but some (many?) drivers are not so comfortable with high body roll.

Basically what I'm saying is what you do with the car's suspension should depend on use and purpose of the car. If you're running the drag strip and taking family trips, that's going to be different goals and compromises than just street use, etc etc.
Step by step, I'd look at the shocks to see what they are and condition. Likely change them out or adjust if they are adjustable.
Ditch the traction bars and check the shackle angles, the pinion angle, and drive shaft angles. For the rear springs to work, there need angles need to be in the correct range and helping the anti-squat. A pinion snubber against the floor will be a big help with drag race slicks, but otherwise shouldn't be needed.
For other than drag strip, bring the t-bars up to the 1" range for all season street tires. .99 to 1.04 is all similar enough I wouldn't sweat it.
For stickier tires and better roads, larger diameter is fine. I've moved up to larger diameters because I got stickier tires for autocrossing and still use it on the street with street tires, even pretty poor roads, without handling issues. The notchbacks tend to be a little nose heavier than fastbacks like a duster, so YMMV.

Note: T-bars in the 1" diameter range ought to have clocked hexes. Firm feel has that figured out when they started making them in house. I beleive PST does now as well (based on posts on this forum).
 
PST's site says the bars have "20 degree" clocking and a 230lb rate. They're also powdercoated.
 
If they don't slip into the hexes, then sand the coating down. Just the coating. Don't force them into the hex, or they are a bitvch to get out.
 
I had always thought my 70 Swinger 340 handled well with stock type front suspension. Ofd course the parts were ner and replaced .
Do you mean stock TYPE suspension (retaining torsion bars, but with beefier and/or improved parts), or actually stock suspension simply with new replacement parts.
I imagine that depends upon what you are comparing it to.
Versus a Tri 5 shoebox, probably handles well
Versus stock with worn out parts, probably handles well
Versus a BMW 3 or Miata, probably not so well- IF truly stock. But "beefier and/or improved parts" on a stock type system can give em a run and possibly a little whuppin

It all depends what you're looking to accomplish.
 
Glad this got bumped, because I need it. The guy that built my Duster was a pretty good wrench...but a Chevy guy and totally unfamiliar with Mopars. As such, he made some...interesting...part selections. I'm 99% sure I have a JS front swaybar, with probably-original .85" bars on the otherwise-totally-rebuilt (PST) front end. (Car is a factory 318.) He coupled this with Super Stock rear springs, too-short underride traction bars, and HD shocks...with the result the front is way soft, and the rear is like a hardtail Harley. :BangHead: Obviously, most of this has to be dealt with.

Though a big-bumper car, my Duster is relatively light (~3300), with a 4-speed and no power options. I was thinking .99" bars (184lb), but this thread has me thinking I might want the 1.04" or even 1.09" MP bars.

Also, I dug up the old tech article about wheel rates from Mopar Action. For 35.8" A-body bars, the rates are...

.81 (MP drag)-82
.83 (slant)-92
.85 (315)-101 (No wonder mine handles like a marshmallow.)
.87 (340)-109
.89 (B/RB)-120
.92 (MP HD)-137
.94 (76 police)-149
.99 (MP)-184
1.04 (MP "HD solo")-224
1.09 (MP circle track)-270
1.14 (MP circle track)-323(!)


1.14 (MP circle track)-323(!)

1.14 T-bars here !!

1670400789140.png
 
1.14 (MP circle track)-323(!)

1.14 T-bars here !!

View attachment 1716019335
Your Barracuda is as cool as it gets, IMO and your car has been an inspiration for my own build in a number of different ways. I too have 1.14" bars in my Sport. :D

While my opinion wavers a bit, I don't think these are the best choice for a street-only car. In order to work properly, I believe a car should have accompanying chassis bracing, performance alignment, and sufficiently grippy radials to put it all to use.
I don't regret my decision but the car rides pretty rough around town and doesn't quite pay off in subjective driving experience.

I suspect they will earn their keep once I have the confidence to get the car onto an autocross course.
 
Your Barracuda is as cool as it gets, IMO and your car has been an inspiration for my own build in a number of different ways. I too have 1.14" bars in my Sport. :D

While my opinion wavers a bit, I don't think these are the best choice for a street-only car. In order to work properly, I believe a car should have accompanying chassis bracing, performance alignment, and sufficiently grippy radials to put it all to use.
I don't regret my decision but the car rides pretty rough around town and doesn't quite pay off in subjective driving experience.

I suspect they will earn their keep once I have the confidence to get the car onto an autocross course.

I agree. I would not advise someone to start off with 1.14" on a 100% street only car. And a car and owner that's not had any previous suspension mods to car.

There's a lot of personal preference here. Maybe if someone already had 1", then wanted to explore more.. Then try 1.14".

I had .99" for 10+ years. And it was my only car then. When I went 1.14" is was a secondary car.
 
I agree. I would not advise someone to start off with 1.14" on a 100% street only car. And a car and owner that's not had any previous suspension mods to car.

There's a lot of personal preference here. Maybe if someone already had 1", then wanted to explore more.. Then try 1.14".

I had .99" for 10+ years. And it was my only car then. When I went 1.14" is was a secondary car.

What size tire/wheel do you run? You look to have much more sidewall than I do, and I have to assume that dampens the ride and affects handling with those 1.14' bars. I think @MRGTX has a larger diameter wheel and perhaps that's the reason it is a bit harsh on the street.
I already get understeer with my 1.08 bars, so I don't even think about putting a stiffer bar on mine. Now I do only have a 235 tire on the front due to my wheel choice and I'm sure that has something to do with it. Since my wheels aren't available with the correct offset/width, I'll likely eventually get them widened to accommodate a 275 on the front. I'm not doing anything to the suspension until I can get a wider wheel up front. Overall, I think my car handles great on the autocross.
 
What size tire/wheel do you run? You look to have much more sidewall than I do, and I have to assume that dampens the ride and affects handling with those 1.14' bars. I think @MRGTX has a larger diameter wheel and perhaps that's the reason it is a bit harsh on the street.
I already get understeer with my 1.08 bars, so I don't even think about putting a stiffer bar on mine. Now I do only have a 235 tire on the front due to my wheel choice and I'm sure that has something to do with it. Since my wheels aren't available with the correct offset/width, I'll likely eventually get them widened to accommodate a 275 on the front. I'm not doing anything to the suspension until I can get a wider wheel up front. Overall, I think my car handles great on the autocross.

I have lousy 245/50/15 tires you can’t get anymore on 15x9 rims

Yes, shorter sidewall will effect ride.

I’m planning on 275/35/18 on 18x9 bare minimum. But looking into 295 and 305 …or maybe more
 
I just did the PST 1.03 torsion bars on my Duster, as well as stock upper control arms with Moog problem solver bushings. The lowers I used the stiffening plates with the Delrin bushings and pivots. as well as QA adjustable strut rods from BAC and a 1" or so Hellwig sway bar. KYB gas shocks on all 4 corners which made a big difference, but the verdict is still out on them. I'm still riding on funky 15" wheels and tires like 275/60 on the back and 215/60 on the front which looks cool, but leaves room for improvement. I'm using going to 17" Mustang Bullet wheels all around which are not my first choice, but at $25 a piece I couldn't pass them and gives it the Torq Thrust look which is my favorite wheel anyway. I did think of spending big money on "tubular" stuff which looks cool and probably works great in the right application but after taking the invaluable advice of @72bluNblu who has some great ideas I decided to throw a little money at what I already have and save the money on stuff we probably don't need for something else like my 72 Demon project which will be getting pretty much the same treatment as well as a slant 6/904 to a nasty 340/727 that a buddy is swapping for a 500 inch motor in his Duster
 
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