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

[Super-Cuda]

All my cars have a properly set up torsion bar suspension. My preference in this hobby is to enjoy the cars the way they came. I like old cars because I like old cars. I like the way they feel on the road, and all of their eccentricities. I can drive any of our daily driven rack and pinion vehicles, but I prefer to drive my Roadrunner. It is a 6bbl, 4 speed, Dana, manual steering, and manual drum brakes. That to me is heaven, just like it was in 1970, and it makes me happy to be able to enjoy it just the way it came.

I came to this thread to read about the HDK front end, and the coil over front systems that are available. I like engineering and figuring things out, not necessarily to apply to my cars, because in my world it takes the feel out of the car. But I don’t bash anybody that wants to enjoy their car in any way they see fit. It’s when someone bashed me for not jumping both feet into their vision for their car that I take offense to. I’m not a road and track racer, but I can certainly appreciate the setup that makes that possible in an old car. It’s just not for me, and I don’t appreciate being dogged about “not reading” the entire post. I don’t need to, I simply answered to the title of the thread.

And, as a matter of reference, when Denny wanted to build his front suspension for early A bodies, I gave him a shell of a car to do his mock up on, because I had it and he needed it. He offered me one of his HDK kits at a really good price, but I declined, because it’s not the way I drive my cars. I just wanted to help him bring his product to the early A guys that do want to drive that way.

Very cool move cosgig!

 

[racerjoe]

@racerjoe any idea how your wheel rates compare between your old set up and new?

I think I covered it in my build thread. I’d have to go back and look. Although, it’s likely changed a bit since I’ve increased track width slightly. Probably not enough to make a difference. For reference, I have 450lb springs now.

 

[J-c-c]

While I haven’t read or been part of all the threads, no one that I have seen has ever calculated the roll center. It’s actually part of what Blu has asked for, for literally years. Better geometry is claimed but no one has ever post any data until this thread.

Maybe someone with an RMS would be willing to take some measurements so we could calculate their roll center?

The other part I am curious about is scrub radius. It’s a separate and different aspect, not really related to a COC, just something that I tripped over while working on something else.

FWIW, it seems those numbers are seldom shared by the manufacturers, which is odd, since they can be measured, and makes one wonder what are they hiding?

 

[J-c-c]

A lot of back and forth here counting angels on the head of a pin it seems.
OP shared some useful info, it works for him, take it or leave it.
Only one maybe minor detail stood out to me nobody has yet mentioned, the not square tire set-up, which effects everything else.
Good handling set-ups usually get close to square.

That being said, the OEM K member is a very robust stout item. With TB's It ties the entire front end together and support and controls the heaviest item in the car, transits all torque reactions the gas pedal generates., and is very much inline in transmitting all front end sprung loads, cornering, steering and braking forces. Lighter weight tubing aftermarket k frames can never match that stiffness, are they acceptable, maybe, but stiffer no way no how, i don't care what material or welding process they use. Is a steering rack better design than a OEM PS box, always. Are better suspension kinematics favored, not matter what the suspension , Yes. The OP seems to have them, Can OEM numbers be improved, maybe, how and at what cost/effort is for the owner to decide. The OP has chosen his path.
I personally have upgraded OEM TB setups, a modified RMS MII set-up, I flew out to Morrison last May to check out their very impressive IFS rack/C6 set-up, but they would not share their numbers after purchase, even with a NDA, so that got put on hold. In the meantime, I'm toying with the C6 MII spindle upgrade option with 2" taller BJ's. since I find the MII spindle and Wilwood Alum hub woefully inadequate on a B Body RB track car with big brakes heat soaking the hubs.

 

[harrisonm]

I have wanted to put in an RMS Alterkation front and Streetlynx rear setup in my 69 Barracuda for years, but I just can't force myself to spend the money. The thing I like about their front setup in that there in no shock tower strengthening required. I seem to remember it needed significant shock tower work.

 

[BergmanAutoCraft]

I'm very late to this party. Tim is a great guy with a nice car too! He mentioned some good points, especially regarding the camber curves. I have some comparison photos on my phone I can add. You will never get an apples/apples comparison. Its like saying my new tires are better than my old ones.

I think the things to take home here are people like a clean bolt in solution with all new parts, regardless of what they do. Others are happy with getting dirty and doing modifications.

In terms of performance, the tires don't care where they get their angles or spring rate from. Excellent performance can be achieve many ways these days.

The things I like about my t bar setup is a good ride, turning radius and suspension travel. My setup uses delrin bushings which last almost forever. The room for tires is huge with 18s. I've run a 275 on the front pretty easily. My on center feel is excellent and the on center tracking is easily as good and my modern cars. The tires remain square throughout the turns maximizing the contact patch. I realize most won't go through the lengths I have to setup and refine like I have, but the results are impressive.

For anyone looking to compare lap times, that's another story entirely. Driving skill and tires are very big factors. Personally, I'm not the greatest driver, and I like to run tires I can use in any temp. Currently running Michelin Pilot Super Sports. 320 TW.

The biggest take away is be thankful there are options. I started navigating handling improvements in 1985, when it was just a joke..

 

[HemiDenny]

..... The thing I like about their front setup in that there in no shock tower strengthening required. I seem to remember it needed significant shock tower work.

top 2 reasons why HDK maintains the OEM upper shock mount, adds a re-enforced upper shock mount with chromoly support hoops

a) without the shock mount hardware in the wheelhouse the HDK upper shock mount / chromoly support hoops affords a considerably narrower track width preferred on most street rides.....with ZERO failures. For a decade, HDK has sold RMS / Alter K owners that removed their shock mounts, added the HDK upper shock mount package and removed / shortened their control arms approx 1".

b) ability to use shocks with greater travel. The greater the travel, the longer the spring. HDK contends that combination affords a better, less harsh ride.

BTW.... tried and proven method is also used on the HDK coil over only package handy when additional room in the engine compartment is needed....or required

 

[HemiDenny]

FWIW, it seems those numbers are seldom shared by the manufacturers, which is odd, since they can be measured, and makes one wonder what are they hiding?

I get asked for all kinds of info which I have learned the hard way to keep propriety. When a call or e-mail asks for specific measurements and technical data, 99% of the time it is simply an attempt to gain info to build their own.

I had one guy tell me because he could not afford to buy one ....I should e-mail him my CAD / DXF files so he could build his own. Best laugh I had that whole year.

 

[Super-Cuda]

A lot of back and forth here counting angels on the head of a pin it seems.
OP shared some useful info, it works for him, take it or leave it.
Only one maybe minor detail stood out to me nobody has yet mentioned, the not square tire set-up, which effects everything else.
Good handling set-ups usually get close to square.

That being said, the OEM K member is a very robust stout item. With TB's It ties the entire front end together and support and controls the heaviest item in the car, transits all torque reactions the gas pedal generates., and is very much inline in transmitting all front end sprung loads, cornering, steering and braking forces. Lighter weight tubing aftermarket k frames can never match that stiffness, are they acceptable, maybe, but stiffer no way no how, i don't care what material or welding process they use. Is a steering rack better design than a OEM PS box, always. Are better suspension kinematics favored, not matter what the suspension , Yes. The OP seems to have them, Can OEM numbers be improved, maybe, how and at what cost/effort is for the owner to decide. The OP has chosen his path.
I personally have upgraded OEM TB setups, a modified RMS MII set-up, I flew out to Morrison last May to check out their very impressive IFS rack/C6 set-up, but they would not share their numbers after purchase, even with a NDA, so that got put on hold. In the meantime, I'm toying with the C6 MII spindle upgrade option with 2" taller BJ's. since I find the MII spindle and Wilwood Alum hub woefully inadequate on a B Body RB track car with big brakes heat soaking the hubs.

My experience with the factory K member in my 68 Barracuda was not as great. Probably caused by lack of maintenance, poor factory weld procedures, etc..

K member cracked in several places, very poor welding, LCA pivot mounts cracked, and major flex in the power steering box mount.

I know all this is able to be repaired but, I'm not a professional welder so I decided to look at options after removing the complete front suspension in my car.



I called several suppliers of aftermarket suspensions and after doing the usual on-line research, RMS came to the top of my list. In all fairness, I did not know about HDK at the time as their product would definitely have been in the running.

The others?? Well, after seeing piss poor welding, shoddy assembly, bad engineering and , at the most expensive place of all, not even getting a call back, I decided on RMS.

The service from Bill at RMS was impeccable. He helped me all the way with spring rates, suggestions on brakes, even made a custom one-off rear sway bar for the streetlynx rear suspension .

Is it better than stock? I think so but, after being schooled by some of the more knowledgeable members on here, I did not know how much better you can make the stock suspension. It does, however, require considerable skill and knowledge of suspension systems and necessitates replacing shocks, control arms, upgrading LCA's and modifying the K-Member as well as the steering box.

It was jut easier with my skill level to replace everything with an aftermarket system and I'm very satisfied with the results.

Love this thread though. Never too late to learn from the pro's.

 

[Super-Cuda]

I'm very late to this party. Tim is a great guy with a nice car too! He mentioned some good points, especially regarding the camber curves. I have some comparison photos on my phone I can add. You will never get an apples/apples comparison. Its like saying my new tires are better than my old ones.

I think the things to take home here are people like a clean bolt in solution with all new parts, regardless of what they do. Others are happy with getting dirty and doing modifications.

In terms of performance, the tires don't care where they get their angles or spring rate from. Excellent performance can be achieve many ways these days.

The things I like about my t bar setup is a good ride, turning radius and suspension travel. My setup uses delrin bushings which last almost forever. The room for tires is huge with 18s. I've run a 275 on the front pretty easily. My on center feel is excellent and the on center tracking is easily as good and my modern cars. The tires remain square throughout the turns maximizing the contact patch. I realize most won't go through the lengths I have to setup and refine like I have, but the results are impressive.

For anyone looking to compare lap times, that's another story entirely. Driving skill and tires are very big factors. Personally, I'm not the greatest driver, and I like to run tires I can use in any temp. Currently running Michelin Pilot Super Sports. 320 TW.

The biggest take away is be thankful there are options. I started navigating handling improvements in 1985, when it was just a joke..

Curious as to what A-Body you are running 18" tires on the front. Did you have to modify the lower part of the fender for clearance?

 

[BergmanAutoCraft]

Curious as to what A-Body you are running 18" tires on the front. Did you have to modify the lower part of the fender for clearance?

The 18s go around the upper ball joint. Front rim is 18x9, 6.38" BS. I chose to remove the fender lips, but 255 40s would fit without doing that.

 

[Super-Cuda]

The 18s go around the upper ball joint. Front rim is 18x9, 6.38" BS. I chose to remove the fender lips, but 255 40s would fit without doing that.

View attachment 1716194909

Thanks very much for the reply.

On my 68 Cuda, it would require trimming the front lower section of the fender to clear 18" from the information I got on here as well as from other sources. Your Dart obviously does not require that mod.

BTW: Cool Car!!!

 

[Dale Davies]

Ahh, the age-old debate of which suspension is better for our beloved Mopars. There will always be opposition when this topic is discussed, but first, what exactly is “better”? Are the things that one person considers “better” actually relevant to everyone? Probably not. Chances are the die hard “coil over suspension is better” guys haven’t driven a properly setup torsion bar car. As the title suggests, I’m going to discuss the HDK Suspension K-Member as it pertains to handling. And by handling, I mean going fast, turning, and keeping up with, if not beating modern cars on an autocross. We all know aftermarket K-members offer lighter weight and extra room for big engines and headers so those topics won’t be discussed.

For reference, I have a 1970 Plymouth Duster that I use for cruising and autocross. I’ve only been autocrossing for a 3.5 years and have approximately 175 autocross runs on the car. I’ve never driven anything else on an autocross course, only this car. Until the summer of 2023, the car was setup with a stock style torsion bar suspension with parts designed specifically for improved handing. My t-bar setup consisted of the following parts.

• Sway a way 1.08 bars
• Hotchkis front and rear sway bar, non-adjustable shocks, and leaf springs
• SPC gen 1 upper control arms
• FMJ Spindles
• Aluminum tie rod sleeves
• QA1 adjustable strut rods
• Fully welded biscuit type K-member and LCAs
• Borgeson steering box
• 14” front discs and 12” rear discs
• Falken Azenis 200TW 235/40-18 front tires, 275/35-18 rear tires
• Alignment- 6.25 degrees caster, 1.5 degrees camber

This combination of parts resulted in a very good handling car. Unlike drag racing where the car with the most HP usually has the fastest car, the same doesn’t hold true on the autocross. Having a properly set up car is probably 75% of the equation. Driver skill is the last piece of the puzzle and is the hardest to make up. There is no replacement for seat time! I’ve never won a big event, nor am I the fastest at any given event. If I were to describe my skill, I’d say I am slightly better than mediocre. My car is always the oldest at my local events and I’m typically within the top 25% of the cars there. Most of which are modern compact cars.

In June 2023, my journey with stock style K-member and suspension ended with the installation of an HDK Suspension K-Member with coil overs and rack and pinion. I honestly didn’t know what to expect. Was I going backwards in my quest to have a 50+ year old car that can hang with modern cars around turns? Was it going to be a night and day difference? There was only one way to find out.

If you have been around the automotive market long enough, chances are you have heard someone say coil overs will be exponentially “better” for your car. But why exactly will this one part make your car better? After all, it’s just a shock with a spring around it. Sure, it can make ride height adjustments easy, but nothing is easier than adjusting the tension on a torsion bar. Fortunately, modern aftermarket suppliers are now manufacturing many options when it comes to larger diameter t-bars and there are plenty of non-adjustable, and adjustable shock options. Therefore, I’d say either option is good from an aftermarket support standpoint. From a assembly/disassembly standpoint, torsion bars can require slightly more work.



So, if we have determined the shock and the spring are the same as a shock and torsion bar, what exactly makes one configuration better or worse than the other? The uninformed won’t know where to go from here, but the big difference is the geometry of the moving components. Chrysler did a good job designing the front suspension. With a FMJ spindle, and a lower ride height, the geometry is pretty darn good. The camber gain with the FMJ spindle has been well documented and can be found online easily. With simply a set up adjustable control arms, you can dial in more caster and camber than you would ever want. Changing the upper ball joint height can further dail in the roll center and camber gain. However, the geometry adjustability pretty much ends with the upper control arm.

Nearly all aftermarket K-Members come with a rack and pinion. By design alone, you will get better steering response. While the Borgeson steering box is a huge improvement over the stock Mopar PS box, the rack is much faster. The Borgeson box is 3.5 turns lock to lock and the rack is 2.5 turns lock to lock. Besides the quicker response, the rack doesn’t have a dead spot in the center position like any steering box will have. There are products out there to quicken the steering box, but I’m not aware of a bolt in solution. This one could go either way based on driver preference because both are good.

Now let’s discuss the HDK suspension. Right away, the adjustability of the lower control arm alone gets a checkmark in the win column over stock components. Just having this one component being adjustable allows track width adjustments, easier caster adjustments, and wheel base adjustments when running aggressive caster. Upper and lower screw in ball joints allow options to use a longer balls joint for dialing roll center adjustments or even opportunity to use non-traditional spindles. More on that later.

Just like almost all coil over conversion for Mopars, the HDK uses a Mustang 2 style spindle. There are many options available when it comes to the M2 spindle. There are inexpensive versions, there’s a Wilwood version that is approximately ½” taller than standard, then there’s a relatively new CPP option that uses the corvette hub and brake assembly. The options for brakes on these spindles seem endless. I chose to use the corvette hub style, mostly to get the much larger sealed bearing and a Wilwood 6 piston caliper. Every car guy wants options, the M2 spindle offers that and it works great for drag racers and cruisers. The biggest problem with the M2 spindle is its very short. HDK remediates some of the height problem by supplying a 1” taller than stock upper ball joint. However, this isn’t enough if you are looking for maximum handling capability. With the shorter spindle, the upper control arm has a downward angle toward the tire. When the suspension compresses, the UCA will push the top of the spindle outward until it gets to the level point before pulling the spindle back in. This results in camber loss. Not a recipe for great handling. The second problem with the UCA having a greater angle than the LCA, is the roll center is in the ground. The short M2 spindle puts a check into the negative column for the coil over conversion, but the good news is, there’s a way to fix this.

The Wilwood spindle will help a little, but it still isn’t tall enough. The first option is to get an even taller upper ball joint. There are several aftermarket ball joint manufacturers that make up to 1” taller ball joints. When it comes time to go beyond that, I was only able to find 2 manufacturers. Howe Racing makes a 1.5” taller and Allstar Performance has a 1.5” and 2” longer option. The pivot point for the UCA and LCA on the inboard side is approximately 12.5” apart. This means the distance between the ball joint pivots needs to be greater than 12.5” to have any chance of getting the control arms into a position that will have a favorable roll center.

In trying to continue using the M2 CPP spindle, I opted for the 2” longer upper ball joint. I was initially concerned about sacrificing strength, but it’s a strong piece. The shank diameter and threads are larger than the 1” longer piece but still has the 7 degree taper. Using the combination of the CPP M2 replacement spindle along with the 2” longer upper ball joint, and the standard lower ball joint supplied by HDK, the ball joint pivots are approximately 13” apart. This gets my roll center to approximately 2.5” above ground.

As of this writing, HDK has been made aware of the 2” longer ball joint and will likely supply it with the kit if requested.

During my quest to refine the geometry, I found Ride Tech is now offering a taller spindle with the corvette hub designed to be used on their Chevelle platform. Based on scaling some pictures found on the internet, it appears the spindle is approximately 2” taller than the standard Mustang 2 spindle. Considering the HDK uses screw in ball joints, even if the Chevelle spindle has a different ball joint taper than the M2, ball joints of the correct taper could be sourced. Like with most GM spindles, the steering arm bolts on. There seems to be endless options on length for this part, so dialing in steering angle would be another adjustable feature. Having a 2” taller spindle will allow use of the ¼”,1/2”,3/4”, and longer ball joints to dial in suspension geometry more precisely. I’m limited now since I’m using the 2” just to get the UCA past parallel.

For the guys that are educated in suspension geometry that state coil over conversion systems don’t have proper camber gain, well, I fixed that. With just the taller ball joint change, the standard HDK camber gain went from .7 degrees at 2” of compression to 1.8 degrees at 2” of compression. The factory suspension with an FMJ spindle is around 1.4 degrees based on an old Mopar Muscle Magazine article. Of course, ride height affects all these measurements so use these values at your own risk.



Back to the question at hand, can the HDK handle better than a T-bar setup? As of this writing, I’m going to say my car is handling better than it ever has. I’ll admit, I never took the time to dial in camber gain and roll center on the factory suspension, so perhaps there are some improvements I left on the table. Let’s just say it’s just as good and move on. The aftermarket doesn’t support our Mopars like other brands, so let’s just embrace the fact that there are companies out there willing to contribute to our brand.

Coil over conversions will never be for everyone. If you’re a die-hard t-bar guy and think coil over conversions are bad, I’d like for you to come ride with me around the cones. I plan to be at every Moparty running Grand Champion as long as I’m vertical. Come introduce yourself and let’s go for a ride. I promise you will have a grin from ear to ear after the first corner.

I would take it your specification of 1.5° camber would be negative.
A friend decided to road race his Duster after a tiff with the drag racing bunch. Upgrsded the front brakes to factory discs and a few other things like an AC water pump. I suggested increasing the caster and starting with 1° negative camber. He could out accelerate a race prepared Sunbeam Tiger on the straight but got passed at the corner. Most corners were right hand so the left front tire pretty much melted the outside two ribs. I tried to get him to pull about 1/4" of shims out of the upper adjustment, but he said his alignment guy knew what he was doing. Obviously not. Pull the shims out and reset toein and good to go, but no dice. Cost him on tires through that summer as the left front had to be replaced after every race weekend.
At the end of the summer he refreshed the engine with rings, bearings and timing chain. Sold it to a kid whose father was a hotshot lawyer. Kid blew the engine within a week. He told the kid the engine had been refreshed but did not put on the bill of sale "no warranties expressed or implied". Had to give the kid back the full purchase price and then find another 340 engine. Kid had missed a shift big time and scattered parts all over the road.

 

[Dale Davies]

The reason for that is obvious. We've preached and preached and preached about how GOOD the original factory suspension systems on these old cars are and it's true. All one has to do is look back at motorsports history and you'll see the stock style Chrysler suspensions were far superior to anything else offered at the time. These cars have won every major type of motorsports event right from the start.

Remember the article about the Movie Bullitt? They went on and on about how much modification the Mustang had to have regarding both power and handling for all of the stunts while the Charger required very little for either. It was essentially stock with a few reinforcements compared to the Mustang. The Charger still left the Mustang in the dust.

While our suspension systems can be improved upon, it's harder to do than just bolting on a few parts.

Agreed. Look at the 70 Challenger and Cuda TransAm race cars. Pretty much one year development against Ford and the General and they performed fairly well. Some private teams had run Valiants and the early Barracudas against factory teams.

 

[Dale Davies]

Thanks very much for the reply.

On my 68 Cuda, it would require trimming the front lower section of the fender to clear 18" from the information I got on here as well as from other sources. Your Dart obviously does not require that mod.

BTW: Cool Car!!!

Bat them. In the tight spot, roll a bat between the tire and the fender. Good to use a heat gun to soften the paint a bit to prevent cracking.

 

[Super-Cuda]

Bat them. In the tight spot, roll a bat between the tire and the fender. Good to use a heat gun to soften the paint a bit to prevent cracking.

I' guessing you are referring to the top of the fender.

The problem comes into play at the lower front part of the fender when turning in or out.
Seems to be a problem for 67-69 Cudas only.

Here's what one of our members did to get required clearance for 18" tires on a Cuda.


1968 Barracuda Front Fender Modification for 26" Tires

 

[BergmanAutoCraft]

I run .5 neg camber. I've found two things. One, more negative camber directly affects tracking over poor surfaces. Second, in my setup the camber gain is good enough that I don't need all that negative static camber. I do run 7.5 degrees caster, taller upper ball joint and F spindles.

 

[DionR]

I get asked for all kinds of info which I have learned the hard way to keep propriety. When a call or e-mail asks for specific measurements and technical data, 99% of the time it is simply an attempt to gain info to build their own.

I had one guy tell me because he could not afford to buy one ....I should e-mail him my CAD / DXF files so he could build his own. Best laugh I had that whole year.

Makes sense why you shouldn’t share mounting points and such. No argument there.

But things like a potential roll center, camber gain, scrub radius, wheel rate, etc. are all easy to calculate and validate (or invalidate) a design and make it easier to compare to other designs. Like comparing CD on different makes of cars, doesn’t expose the design but it gives hard numbers to compare when one design says “better aerodynamics“.

Certainly things like ride height, alignment and wheel/tire sizes can have a huge impact on those numbers making an apples to apples comparison hard. But honestly, if I was marketing a kit as having better geometry, first thing I would do is drag in a stock car, standarize those values and take some measurements. Then I would set up my kit the same way and if they were improved I would publish them every place I could. But I don’t see anyone doing that which makes me wonder…

I understand that you aren’t making that claim, not pointing this at you. But there are other companies that do make that claim, without anything to back it up. And based on the OP’s initial set up, I would bet at the very least the roll center is not better on those other kits.

It’s not like the stock suspension has to be all that modified either. Toss on an adjustable UCA and leave the rest alone. Bolt up a 17” or 18” tire similar to what the COC would run and match the ride height. Then give it an alignment of something like -0.5 camber and +6 caster and take measurements of the pivot points. Then cycle the suspension and measure the camber gain. With that someone would have a baseline and could set up a COC with the same values and take the same measurement and actually see if their suspension had better geometry.

I understand why they don’t though. Most people in the community believe a COC is better, so why spend time and money to prove it when it might not be true and it’s already generally accepted.

 

[DionR]

I run .5 neg camber. I've found two things. One, more negative camber directly affects tracking over poor surfaces. Second, in my setup the camber gain is good enough that I don't need all that negative static camber. I do run 7.5 degrees caster, taller upper ball joint and F spindles.

Interesting that you run an extended UBJ. I thought about lengthening the top of my fabricated spindle as part of the project but figured the initial pass would use the stock geometry and I would look at that aspect afterwards. Sounds like a worthwhile direction if the project ever comes to fruition.

 

[Super-Cuda]

For those,(like me) who didn't know or understand what roll center is and how it affects your car, listen to this.

 

[BergmanAutoCraft]

Interesting that you run an extended UBJ. I thought about lengthening the top of my fabricated spindle as part of the project but figured the initial pass would use the stock geometry and I would look at that aspect afterwards. Sounds like a worthwhile direction if the project ever comes to fruition.

While the taller spindle package raises roll center, it shortens the moment arm. This reduces body roll. It’s a neat way to reduce roll couple while achieving good handling and maintaining ride quality. Look at how tall OE spindles are on front suspensions that use typical double A arms.

 

[DionR]

Here’s an interesting read on the shortcomings of an early Camaro front suspension design. Start at point 2, about halfway down, if you don’t want to read the whole thing.

Why are old Camaros always so slow? – J-Rho's '67 Camaro Z28 STX build

Highlights how the spring and shock location results in very height spring rates and difficult shock tuning. I can convinced that an early Camaro (and probably most GM products) really do need a COC.

 

[Super-Cuda]

While I haven’t read or been part of all the threads, no one that I have seen has ever calculated the roll center. It’s actually part of what Blu has asked for, for literally years. Better geometry is claimed but no one has ever post any data until this thread.

Maybe someone with an RMS would be willing to take some measurements so we could calculate their roll center?

The other part I am curious about is scrub radius. It’s a separate and different aspect, not really related to a COC, just something that I tripped over while working on something else.

If I can move some things around in the garage I will be willing to take the measurements and post them. I would love to have as much info as I can get about the Alterkation setup in my car.

PM me if you want with the measurements required and I'll get them.

 

[DionR]

I think I covered it in my build thread. I’d have to go back and look. Although, it’s likely changed a bit since I’ve increased track width slightly. Probably not enough to make a difference. For reference, I have 450lb springs now.

Sure enough, you did. Looks like your 450# springs are about the same rate as a 1.12 TB which is up from the 1.08 bars you were running before the change.

I was just curious if the spring rate had been maintained between the 2 setups. Just a data point.

 

[DionR]

If I can move some things around in the garage I will be willing to take the measurements and post them. I would love to have as much info as I can get about the Alterkation setup in my car.

PM me if you want with the measurements required and I'll get them.

Love to see them. No reason to keep them a secret though, right?

Soon as I can, I plan to measure my Duster and will post them as well. But it will be months for various reasons.