DOES THE HDK SUSPENSION K-MEMBER HANDLE BETTER THAN A T-BAR SUSPENSION?

[HemiDenny]

I luv the different Mopar taller spindle possibilities, sounds like the same affect as utilizing longer stud upper ball joints, but just so I fully understand..... the OEM upper ball joint location / position while OK for your grocery getter / hot rod, may not be optimum for other applications, say like auto-X

I think I got it.

 

[HPP]

Correct. A taller spindle produces a similar effect as a longer stud ball joint. However, since a spindle also has inclination built into it, a spindle change can also impact camber gain, upper control arm length, dynamic caster change, roll center migration, etc. I believe the stock spindle SAI is around 5*. They stock car units I pictured above have 8*. The taller height also increases the dynamic camber gain of the system because it has shortened the effective length of the upper arm as it's static mounting angle is increased, but this same change applies to the longer ball stud change.

However, you need to be mindful of the impact on the whole package. Taller spindles tend to raise the front roll center, which seems counter-intuitive to handling, until you realize that raising the front roll center shortens the moment lever arm, thus reducing the leverage creating body roll. If you are not changing the rear roll center, this can be helpful. This is the approach that Peter and Joe have taken with the changes in spindle height/ball joint length that they utilize on their cars. I suppose you could raise this high enough to be even with or above the rear location. While a very, very short lever arm may be desirable, I have no idea what a reverse situation would be like. I doubt it would be an improvement and don't know what kind of detriment it may produce without doing some digging through some of my reference material.

The ideal would be to lower the roll centers on both ends as low as possible, then minimize the lever arm length to reduce the roll. However, changing the roll center location on a leaf spring car is very dficult as it's pretty much locked in with the spring eye to axle housing centerline relationship. Unless you turn both leaf spring eyes into flexible pivots, use the leaf as a locating device, then add a panhard bar or watts link to create roll center height location. This is what the race TA/AAR cars of 1970 did.

Another option I don't include in the picture, since I don't have any, is the '73 C body spindles. These use the same large bearings and ball joints as the large A body units. They lower ball joint spread is slightly norrower but can be milled to mount the stock lower ball joint. They are .625" taller than the A body disc spindle (.250 taller than the FJM spindle) and also include a .625" drop in ride height because of the location of the bearing pin.

One caution to using the C body spindle is that C body rotors are thicker than ABE rotors and would require you use the matching C body caliper or something that would fit it like Wilwood, Baer, or Viper. The extra mass of the rotors also would be a good thing for a road race or oval track application. Not sure if the extra unsprung weight is necessarily a good thing if you are optimizing for autocross.

 

[DionR]

There is a limit to how tall the spindle can get, too. It takes a fairly large positive offset to get a big wheel and tire under the fender. This means that things like the steering arm and the UBJ need to fit inside the wheel. Unless we do something crazy with it and move the UCA mount up and use something like the Challenger knuckle where it swoops around the tire and puts the UBJ above the tire.

With my custom knuckle layouts, it appears we are limited to effectively an F-Body spindle and 1" longer UBJ to keep it inside the wheel. Anything taller than that and the 18" wheel won't fit over it, or we would have to run a narrower wheel/tire. Or fender flairs.

 

[DionR]

I luv the different Mopar taller spindle possibilities, sounds like the same affect as utilizing longer stud upper ball joints, but just so I fully understand..... the OEM upper ball joint location / position while OK for your grocery getter / hot rod, may not be optimum for other applications, say like auto-X

I think I got it.

The stock A-Body spindle and UBJ returns a higher RC than Joe's per his last report on it, and thus a shorter roll couple. Assuming the car is lowered. So it can't be worse than a optimized HDK setup. And if bolt on parts like a taller F-Body spindle and longer UBJ make it even better, why not?

At the same time, you make it sound like the TB guys are cheating when they look to make it better while pretending it's ok for Joe to do it to your setup.

Either way, I don't see a problem with trying to make things even better regardless of which type of suspension it is.

All that said, there are still conflicting theories about "best". @HPP references the idea that a roll couple should be kept short. I've also heard a tall RC makes for jacking issues and that the RC should be closer to 3" above ground. I've wondered if a lower RC works well on a car with a low CG, but at the same time, I have referenced in the past the guy with a '67 or '68 Cuda that swears that the 2-3" range is best. All that to say, I'm still unsure what the "best" is.

 

[NC Engine Builder]

The "kit cars" back in the day, used the "c" body spindle, in conjunction with the "b/e/" body front k frame and front frame rails.

 

[HemiDenny]

At the same time, you make it sound like the TB guys are cheating when they look to make it better while pretending it's ok for Joe to do it to your setup.

not at all,

just highlighting my 10,000 foot view from some of the comments on this thread.

....when tuning and making changes on the OEM, those changes are considered simply optimizing, but when Joe tuned on his HDK......some inferred it was because of poor design. My contention is.....same as the OEM, optimizing IS for each particular application. The fact that I believe some changes are easier with a HDK COC.....I consider just another plus.

 

[NC Engine Builder]

not at all,

just highlighting my 10,000 foot view from some of the comments on this thread.

....when tuning and making changes on the OEM, those changes are considered simply optimizing, but when Joe tuned on his HDK......some inferred it was because of poor design. My contention is.....same as the OEM, optimizing IS for each particular application. The fact that I believe some changes are easier with a HDK COC.....I consider just another plus.

It's been 68 years since Chrysler designed the torsion bar suspension, so a little tweak here or there would seem reasonable. Your suspension was designed in what would be considered "modern" times, with many more years of data to examine, so why would your design need ANY tweaks?

 

[DionR]

....when tuning and making changes on the OEM, those changes are considered simply optimizing, but when Joe tuned on his HDK......some inferred it was because of poor design.

I disagree Denny. No one on here that is any kind of a hot rodder would say optimization shouldn't happen, whether it is a Ferrari or a Pinto. Point isn't where you start, but making whatever it is you start with better.

Certainly there has been discussion on the design, but you get that regardless of what it is. Look at the many arguments over the years over "wagon wheels" and people hating the idea of putting a 17" or 18" wheel and performance rubber on a car. Or EFI. Or G3 Hemi swaps. Heck, what about LS swaps? People are going to disagree with you, sometimes over the dumbest of stuff. So what.

But if you can't get over it and you let some internet troll get the better of you, you are losing. Who care's if they call you an asshole, or doubt your knowledge. Big deal, roll on with your life and I bet they will roll on with theirs.

 

[TT5.9mag]

The original torsion bar design was not engineered or designed to be a performance piece, in any sense of the word. Therefore when performance is the goal, optimization or modification is necessary.
The HDK front end was built, designed, (dare I say engineered) to be a performance piece from the start, was it not? Therefore modification and/or optimization shouldn’t be necessary. I believe that is the argument being made.

 

[RustyRatRod]

not at all,

just highlighting my 10,000 foot view from some of the comments on this thread.

....when tuning and making changes on the OEM, those changes are considered simply optimizing, but when Joe tuned on his HDK......some inferred it was because of poor design. My contention is.....same as the OEM, optimizing IS for each particular application. The fact that I believe some changes are easier with a HDK COC.....I consider just another plus.

Everything has to be tuned and optimized. To say something is a poor design just because you have to tune on it is kinda dumb. I wanna see anybody set a car up in the shop and then go out and run an absolutely optimal time with no tuning. Ain't gonna happen cappin. lol

 

[TT5.9mag]

Everything has to be tuned and optimized. To say something is a poor design just because you have to tune on it is kinda dumb. I wanna see anybody set a car up in the shop and then go out and run an absolutely optimal time with no tuning. Ain't gonna happen cappin. lol

I don’t think anyone disagrees with that. And if we all agree on that then definition becomes important. Tuning or optimizing is not the same as modifying. IMO. When you get in to changing roll center, spindle heights, mount locations, and things like that you are changing the design. That is not the same as a spring rate change or a sway bar adjustment.

 

[92b]

The original torsion bar design was not engineered or designed to be a performance piece, in any sense of the word. Therefore when performance is the goal, optimization or modification is necessary.
The HDK front end was built, designed, (dare I say engineered) to be a performance piece from the start, was it not? Therefore modification and/or optimization shouldn’t be necessary. I believe that is the argument being made.

I think the argument being made is a straight up comparison between apples and oranges being made by people who can't agree on what it is that makes an apple an apple and an orange an orange.. Which is also the very reason this argument is so compelling.

 

[HemiDenny]

The original torsion bar design was not engineered or designed to be a performance piece, in any sense of the word. Therefore when performance is the goal, optimization or modification is necessary.
The HDK front end was built, designed, (dare I say engineered) to be a performance piece from the start, was it not? Therefore modification and/or optimization shouldn’t be necessary. I believe that is the argument being made.

For the HDK, it was designed for the sole purpose of making (my) engine swap(s) easier.....the adjustability, dropping some nose weight, the modern feel the rack and pinion offers..... all turned out to be additional benefits.

HDK remains in the market because hot rodding Mopars and the challenges that come with it... are my life.
Can't speak for RMS, Control Freak, Magnum Force.....maybe they will chime in (cough / cough)
Gerst saw a market, got in, sold to Qa1 and is gone. Qa1 and (IMO) ALL of the rest, with the exception of RMS, sees us only as a number on the bottom line.

 

[DionR]

FYI, it was just announced that Control Freaks has been purchased by BMR.

 

[HPP]

All that said, there are still conflicting theories about "best". @HPP references the idea that a roll couple should be kept short. I've also heard a tall RC makes for jacking issues and that the RC should be closer to 3" above ground. I've wondered if a lower RC works well on a car with a low CG, but at the same time, I have referenced in the past the guy with a '67 or '68 Cuda that swears that the 2-3" range is best. All that to say, I'm still unsure what the "best" is

Agreed, I'm unsure what is best. I've seen the commentary from the experienced road racer around 2" being optimal, yet to get here he did major modification to the spindle. Much of my reference material refers to 4" as being optimal and says there can be drawbacks from going too low. I will admit most of my material is from the '90-00s and could be outdated to a degree, but there is still the combination that needs to be considered, and the rear roll center and COG height are two additional, large factors in a classic Mopar combination that are not easily changed.

The "kit cars" back in the day, used the "c" body spindle, in conjunction with the "b/e/" body front k frame and front frame rail.

Yep, they sure did. I also suspect they used the 70-72 and 74-78 version since they have larger C body ball joints that the 73 didn't use, and since oval track is a contact sport and all. While I have a stash of Kit Car literature, I do not have any of the blueprints on layouts to confirm geometry, although I would suspect they have roll centers in the 3-4" range.

I also have never heard of anyone that has had any access to the TA/AAR geometry plots either. As factory supported efforts, I'd be willing to bet these guys were given access to the factory parts bins, the Hustle Stuff catalog of the day, and I wouldn't be surprised at all if they had conversations with Petty, Arrington, or Owens as well. The origins of all these programs allowed Mopar to springboard their info into the Kit Car program for the layman racer. Petty was closely involved with development of the Kit Car and did a lot of testing on the original mule built with a Challenger body.

 

[Mopar_Taxi_Guy]

I know if I was building a B-body for handing and had to venture away from torsion bars this is the kit I'd be spending my money on.

If I was building an A-body for handing and had to venture away from torsion bars, I'm really not sure where I'd be ordering from since AME doesn't build an A-body kit.

I've I was building an A or B-body oriented more towards drag racing and needed to get away from torsion bars it's really a toss up on what kit to buy.

 

[DionR]

If I was going away from torsion bars, I think I would do a generic kit from Detroit Speed or something similar. Something that isn’t using the stock UCA mounts and is engineered for handling. Remove the compromise and start from scratch.

 

[HemiDenny]

If I was going away from torsion bars, I think I would do a generic kit from Detroit Speed or something similar. Something that isn’t using the stock UCA mounts and is engineered for handling. Remove the compromise and start from scratch.

Let me be the first to help, .....and you could call it the WCS (woulda / coulda / shoulda), or the RB (railbird / just fits for me)....or better yet, the IBFN (if / buts / fruits / nuts)

Can't wait to see how you handle the simple challenge of the wide Mopar frail rails with the "generic " kit.

 

[HemiDenny]

I know if I was building a B-body for handing and had to venture away from torsion bars this is the kit I'd be spending my money on.

View attachment 1716460680

If I was building an A-body for handing and had to venture away from torsion bars, I'm really not sure where I'd be ordering from since AME doesn't build an A-body kit.

I've I was building an A or B-body oriented more towards drag racing and needed to get away from torsion bars it's really a toss up on what kit to buy.

I bet I know why they haven't build an A body piece.... For starters , they likely know what cheap suckers we are and what you see is not for the weak in the wallet.

Sure is pretty though. They did a nice job of adding the RMS / AlterK upper shock mount to their Chebbie platform. BTW, nice work guys!!!!..... way to innovate!!!

 

[DionR]

Let me be the first to help, .....and you could call it the WCS (woulda / coulda / shoulda), or the RB (railbird / just fits for me)....or better yet, the IBFN (if / buts / fruits / nuts)

Can't wait to see how you handle the simple challenge of the wide Mopar frail rails with the "generic " kit.

Took that personally, did ya?

If I was going to go all in and spend a chunk of change, why would I not want something that was designed from the start to be a performance handling piece? You yourself said your kit was designed for making a motor swap easier, and handling never entered the chat beyond designing out bump steer.

For the HDK, it was designed for the sole purpose of making (my) engine swap(s) easier.....the adjustability, dropping some nose weight, the modern feel the rack and pinion offers..... all turned out to be additional benefits.

???????????? so where do I EVER claim better geometry or handling ? actually it is the opposite

On the other hand, the Chebby boys have had to deal with a truly subpar design in the Camaro and had to actually design a completely new suspension for the purpose of handing.

So why not go with a blank slate design that isn't tied to keeping the stock UCA mount? Even if the fab work is certainly much more intense.

On the other hand, if I am going to stay with something that wasn't designed for handling, why not stick with what I have? Saves me a ton of cash and avoids things like loading the frame rails in ways they weren't designed for. Plus I get an actual crossmember tying the frames together instead of a single tube. For my purposes, I think the torsion bars will do fine.

BTW, here's a fun read of a Valiant build and his success in a competitive CAM-T arena, despite being 200+ HP behind the competition

Here's one of his event results. Note that even his co-driver beat the Camaro, so it's not just the driver.

And would you look at that, he even beat all the modern muscle that day. But no 1LE's, GT350's or Mach1's since it was before their time so probably not a fair comparison.

Here's the Camaro they both beat that day:

"Under the hood beats a fiery Mast Motorsports LS3-based 427ci engine that delivers 496 hp to the rear tires, as dyno’d by Westech Performance. It’s backed by a TREMEC T-56 Magnum transmission and Currie Enterprises full-floating rear axle. Carbon-fiber inner fenders from Anvil Auto help tuck massive 18x11 Forgeline wheels and sticky Falken Azenis RT615K+ 315/30ZR18 tires.

The car’s tunnel-vision inducing grip comes courtesy of a Total Cost Involved (TCI) Pro Touring IFS in the front and Torque Arm suspension in the rear. The thoroughly modernized setup uses performance-oriented geometry and extremely stiff components to help the car grip into the corners and plant the power on the way out. JRi coilovers sit at all four corners and aid in the grip-making magic."

Chad Ryker’s ’68 Camaro is a Pro Touring Machine You Could Drive Every Day

If there was one gauge in the dash that could measure fun, what would it be? Would it measure adrenaline-inducing rpm? Seat-pinning boost? We’d argue that such

www.motortrend.com

Hmm...maybe the Chebby kit's aren't worth the squeeze.

Wonder how Tom would have done in his Valiant with a 600hp G3/T56 setup? Oh, and bigger torsion bars. Towards the end of the build thread he was toying with upgrading from the 1.06 bars he was running, but never did. Plus, he never got bigger than the 11.75" brakes with some small 4p Wilwood calipers using an AFEngineering kit. Seems like he left some on the table.

Car got sold because his sponsor wanted a different brand:

1967 Plymouth Valiant Sorted 2015 Autocross Winner, USCA, $18K obo

Up for sale is my fully sorted 1967 Pro Touring Valiant. I started with an original CA Black Plate car, built it up using Hotchkis components to be a budget friendly competitive CAM car. I had a great time racing it this year, and winning the local SCCA CAM class year end Championship. I...

www.pro-touring.com

 

[HemiDenny]

Took that personally, did ya?

If I was going to go all in and spend a chunk of change, why would I not want something that was designed from the start to be a performance handling piece? You yourself said your kit was designed for making a motor swap easier, and handling never entered the chat beyond designing out bump steer.





On the other hand, the Chebby boys have had to deal with a truly subpar design in the Camaro and had to actually design a completely new suspension for the purpose of handing.

So why not go with a blank slate design that isn't tied to keeping the stock UCA mount? Even if the fab work is certainly much more intense.

On the other hand, if I am going to stay with something that wasn't designed for handling, why not stick with what I have? Saves me a ton of cash and avoids things like loading the frame rails in ways they weren't designed for. Plus I get an actual crossmember tying the frames together instead of a single tube. For my purposes, I think the torsion bars will do fine.

BTW, here's a fun read of a Valiant build and his success in a competitive CAM-T arena, despite being 200+ HP behind the competition

View attachment 1716460831

View attachment 1716460835

Here's one of his event results. Note that even his co-driver beat the Camaro, so it's not just the driver.

View attachment 1716460836

And would you look at that, he even beat all the modern muscle that day. But no 1LE's, GT350's or Mach1's since it was before their time so probably not a fair comparison.

Here's the Camaro they both beat that day:

"Under the hood beats a fiery Mast Motorsports LS3-based 427ci engine that delivers 496 hp to the rear tires, as dyno’d by Westech Performance. It’s backed by a TREMEC T-56 Magnum transmission and Currie Enterprises full-floating rear axle. Carbon-fiber inner fenders from Anvil Auto help tuck massive 18x11 Forgeline wheels and sticky Falken Azenis RT615K+ 315/30ZR18 tires.

The car’s tunnel-vision inducing grip comes courtesy of a Total Cost Involved (TCI) Pro Touring IFS in the front and Torque Arm suspension in the rear. The thoroughly modernized setup uses performance-oriented geometry and extremely stiff components to help the car grip into the corners and plant the power on the way out. JRi coilovers sit at all four corners and aid in the grip-making magic."

http://[URL]https://www.motortrend....pro-touring-machine-you-could-drive-every-day

[/URL]

Hmm...maybe the Chebby kit's aren't worth the squeeze.

Wonder how Tom would have done in his Valiant with a 600hp G3/T56 setup? Oh, and bigger torsion bars. Towards the end of the build thread he was toying with upgrading from the 1.06 bars he was running, but never did. Plus, he never got bigger than the 11.75" brakes with some small 4p Wilwood calipers using an AFEngineering kit. Seems like he left some on the table.

Car got sold because his sponsor wanted a different brand:

http://[URL]https://www.pro-touring...ant-Sorted-2015-Autocross-Winner-USCA-18K-obo

[/URL]

Great post.....if anything, you talk a good game. Reality is, the ones that do all the squawking (regarding COCs) seem to be the ones that have never even laid a hand on one. It is (almost) funny.

I might of called you an asshole, but I think you deserved it. But I get it, my own brother (RIP Bro John) was just like you. He knew everything about everything, read every automotive article known to mankind.....but couldn't build ****. He was more than my older brother, he was my friend and mentor. One can only image what we called one another.

 

[Mopar_Taxi_Guy]

Does any one know where these two cars ended up?

 

[Mopar_Taxi_Guy]

If I was going away from torsion bars, I think I would do a generic kit from Detroit Speed or something similar. Something that isn’t using the stock UCA mounts and is engineered for handling. Remove the compromise and start from scratch.

If you're going to go to all that trouble you might as well just put a chassis under the entire car and call it a day.

 

[Kern Dog]

Does any one know where these two cars ended up?
View attachment 1716460888

The red car was owned by a guy in Northern CA Bay Area, he sold it to a guy closer to Sacramento, a FABO member. That guy sold it and from there I don't know. I was told that it is a pretty rough car to drive on the street due to the suspension and drivetrain being optimized for track use.

 

[DionR]

If you're going to go to all that trouble you might as well just put a chassis under the entire car and call it a day.

Valid.

Do they even make a chassis for an A-Body? Bet it is 3x more costly than a front clip.

Edit - Schwartz sells one. $26,7K with 14" brakes, double adjustable shocks, full floater 9" with an aluminum center, no powder coating and no assembly. The DSE X-Gen with double adjustable shocks and no powder coating is $9.3K.

Same Schwartz chassis with their IRS is $35,5K. Yikes!