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

[mopowers]

Speaking of RMS, here are my upgrade's that IMO addressed areas I felt needed some simple and little weight gain improvements, that gained some measurable stiffness improvements, and with the weight penalty of less than 10lbs, and all had below the COG. There is more here that this Pic doesn't show, for instance the shock/spring towers are fully boxed now.

What were the measurable stiffness improvements from your modifications?

 

[DionR]

FWIW, Ron Sutton says any measurements that are >1/8" off in measurements, pretty much makes all calculations meaningless. less than 1/16" should be the goal he suggests for the DIY tuner. This was shared at one of his in-depth seminars that covered this topic years back.

Ron Sutton Race Technology :: Hardcore Parts & Tech Support

I did use a set of digital calipers for my measurements, best I could do.

 

[J-c-c]

What were the measurable stiffness improvements from your modifications?

I'll have to look it up. This pic is one test I ran. I calculated an amount of inward force the k member might see on the upper shock/springs mounts, ignoring any contribution the body might provide when bolted together, as before and after was my goal. In this pic I believe you are seeing 425? lbs pulling both mounts straight inward as a portion of the force they will see with the angled springs, and measured movement before and after modification vs relaxed. The difference was not startling, but enough for me to justify the effort, and I suspect way more then say any LCA reinforcement will ever measure.

Sorry, I couldn't resist.

 

[J-c-c]

BTW I am not endorsing Ron Sutton in any way, he seems to lately have gained a slightly tainted reputation according to others.
I consider my source credible.

 

[AndyF]

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.

When I was helping Tim with his red Valiant we looked at all of the coil over kits on the market. That was a few years ago so things have changed a bit. But back then we came to the conclusion that the only benefit was the better steering. The FMJ knuckle was a good height, was very sturdy and we had good brake options. The coil overs were more adjustable, but that wasn't really a big concern. The M2 knuckle was short and not very robust. We ended up staying with the torsion bar design although everything was modified. We eventually ended up building a lot of parts ourselves just to get the packaging correct.
If I was doing it again today I might come to a different conclusion. It really comes down to budget and what the desired results are. For a competitive car I'd build a twin a arm suspension. For a street car I'd stay with stock stuff. For a serious drag race car I would go with struts.

 

[DionR]

When I was helping Tim with his red Valiant we looked at all of the coil over kits on the market. That was a few years ago so things have changed a bit. But back then we came to the conclusion that the only benefit was the better steering. The FMJ knuckle was a good height, was very sturdy and we had good brake options. The coil overs were more adjustable, but that wasn't really a big concern. The M2 knuckle was short and not very robust. We ended up staying with the torsion bar design although everything was modified. We eventually ended up building a lot of parts ourselves just to get the packaging correct.
If I was doing it again today I might come to a different conclusion. It really comes down to budget and what the desired results are. For a competitive car I'd build a twin a arm suspension. For a street car I'd stay with stock stuff. For a serious drag race car I would go with struts.

View attachment 1716196861

View attachment 1716196862

View attachment 1716196863

You didn’t happen to calculate the roll center of that car, did you?

 

[AndyF]

You didn’t happen to calculate the roll center of that car, did you?

No, we didn't care about the theory. We just lowered the car until we ran out of room and that was that. Suspension travel was the biggest issue on the car. What we needed was a dropped front spindle but nobody made a good one. There was a piece of junk on the market back then, but after we looked at it we decided to just stay with the FMJ knuckle. I thought about building my own knuckle but eventually decided not to.
A really high quality forged version of the FMJ knuckle with an inch of drop built in would help these cars a bunch. Should be a money maker since the volume would be decent. Doctor Diff and I exchanged some drawings at one point but we didn't take it any further.

 

[DionR]

No, we didn't care about the theory. We just lowered the car until we ran out of room and that was that. Suspension travel was the biggest issue on the car. What we needed was a dropped front spindle but nobody made a good one. There was a piece of junk on the market back then, but after we looked at it we decided to just stay with the FMJ knuckle. I thought about building my own knuckle but eventually decided not to.
A really high quality forged version of the FMJ knuckle with an inch of drop built in would help these cars a bunch. Should be a money maker since the volume would be decent. Doctor Diff and I exchanged some drawings at one point but we didn't take it any further.

I’ve been toying with a fabricated spindle idea and one of the things that cropped up was the idea of a 1” drop. But when I looked at the outer tie rod clearance issues with a deep 17” wheel and a standard height spindle I figured it wasn’t going to work even with an 18” wheel. The barrel of the wheel needs to come pretty far in to get a big tire on the front and a 1” drop in the spindle seemed like it would limit the tire size pushing things backwards.

 

[goldduster318]

Geometry and having a rack aside...all the coilover kit k-frames on the market seemingly have some similar comprimises which are on the surface pretty bad for a cornering car. I know that generally front steer rack driving vehicles feel better. These things have their place but clearly not anywhere near optimized for handling.

1st: Generally made out of cut plate and square tubing at right angles with no gussets or triangulation whatsoever. This might be just fine for a drag only car and possibly a street car but there's nothing stopping any of these from parallelagraming other than the wall thickness which has a minor effect. The entire car does this to some extent also but not having the OEM k-frame in my opinion makes this more likely. The OEM K-shape is much better for this and it also has vertical height in the middle which would resist bending and torsion. The sway bar mounts like this have to just be flexing left and right since they are basically on horns sticking out. It's a real area that can be improved. Another tie bar in front back to the rails of the k-frame, gussets, smaller square tubing with triangulation would make a serious difference.

2nd is the LCA with the narrow pitch of the two pivot points. Generally, you want is further apart for stability as you find in nearly all modern cars but how to totally solve this using a front steer rack and such a low pivot point, I am not sure. You'd almost need to go with a strut rod that would ride above the tie rods but this might not be possible. In an original Mustang II / Pinto the strut rod goes to the rear direction but on an A-body it wouldn't have much support even if there was a pickup point due to the location of the k-frame bolts without welding something to the stock frame rails. The pivot points being low is also inviting more flex to the k-frame and movement under load.

Really, the first part you could beef it up yourself.

These make sense on drag cars for sure, or for something like a Gen 3 hemi or whatever street car.

Did you figure out the tire size limitation on the front from the K-frame? It was quite easy to put the 275-35-18s in the car in my case with the stock stuff, so was suprised to see such narrow tires.

 

[J-c-c]

Geometry and having a rack aside...all the coilover kit k-frames on the market seemingly have some similar comprimises which are on the surface pretty bad for a cornering car. I know that generally front steer rack driving vehicles feel better. These things have their place but clearly not anywhere near optimized for handling. In all fairness for those who remember when the much now copied RMS IFS first appeared nearly 2 decades back, it was not promoted as a "handling improvement" solution, more a weight, header, and oil pan clearance improver, That IMO has never changed nor has the overall design.

1st: Generally made out of cut plate and square tubing at right angles with no gussets or triangulation whatsoever. This might be just fine for a drag only car and possibly a street car but there's nothing stopping any of these from parallelagraming other than the wall thickness which has a minor effect. The entire car does this to some extent also but not having the OEM k-frame in my opinion makes this more likely. I agree and a point often overlooked The OEM K-shape is much better for this and it also has vertical height in the middle which would resist bending and torsion. The sway bar mounts like this have to just be flexing left and right since they are basically on horns sticking out. I agree they are rather unsupported and a good candidate for flexing, but not left and right literally, more vertically It's a real area that can be improved. RMS has that issue under control IMO Its also interesting that so many are concerned with flexing of OEM LCA control arms by the moments induced by a swaybar they feel it requires a bottom welded gusset, here in this example all those concerns seem to be just forgotten Another tie bar in front back to the rails of the k-frame, gussets, smaller square tubing with triangulation would make a serious difference.

View attachment 1716197089

2nd is the LCA with the narrow pitch of the two pivot points. Not shown in pic #121 is I upgraded the cross shaft to 4130.Generally, you want is further apart for stability as you find in nearly all modern cars but how to totally solve this using a front steer rack and such a low pivot point, I am not sure. You'd almost need to go with a strut rod that would ride above the tie rods but this might not be possible. In an original Mustang II / Pinto the strut rod goes to the rear direction but on an A-body it wouldn't have much support even if there was a pickup point due to the location of the k-frame bolts without welding something to the stock frame rails. The pivot points being low is also inviting more flex to the k-frame and movement under load I also get a kick out those who promote 11/16" vs 9/16" TR but accept freely stacked single shear TR ends with a measly 1/2"? steering rod.

Really, the first part you could beef it up yourself. Reply #121 above addresses many of these concerns, but not solve.

These make sense on drag cars for sure, or for something like a Gen 3 hemi or whatever street car.

Did you figure out the tire size limitation on the front from the K-frame? It was quite easy to put the 275-35-18s in the car in my case with the stock stuff, so was suprised to see such narrow tires.

 

[Dale Davies]

Geometry and having a rack aside...all the coilover kit k-frames on the market seemingly have some similar comprimises which are on the surface pretty bad for a cornering car. I know that generally front steer rack driving vehicles feel better. These things have their place but clearly not anywhere near optimized for handling.

1st: Generally made out of cut plate and square tubing at right angles with no gussets or triangulation whatsoever. This might be just fine for a drag only car and possibly a street car but there's nothing stopping any of these from parallelagraming other than the wall thickness which has a minor effect. The entire car does this to some extent also but not having the OEM k-frame in my opinion makes this more likely. The OEM K-shape is much better for this and it also has vertical height in the middle which would resist bending and torsion. The sway bar mounts like this have to just be flexing left and right since they are basically on horns sticking out. It's a real area that can be improved. Another tie bar in front back to the rails of the k-frame, gussets, smaller square tubing with triangulation would make a serious difference.

View attachment 1716197089

2nd is the LCA with the narrow pitch of the two pivot points. Generally, you want is further apart for stability as you find in nearly all modern cars but how to totally solve this using a front steer rack and such a low pivot point, I am not sure. You'd almost need to go with a strut rod that would ride above the tie rods but this might not be possible. In an original Mustang II / Pinto the strut rod goes to the rear direction but on an A-body it wouldn't have much support even if there was a pickup point due to the location of the k-frame bolts without welding something to the stock frame rails. The pivot points being low is also inviting more flex to the k-frame and movement under load.

Really, the first part you could beef it up yourself.

These make sense on drag cars for sure, or for something like a Gen 3 hemi or whatever street car.

Did you figure out the tire size limitation on the front from the K-frame? It was quite easy to put the 275-35-18s in the car in my case with the stock stuff, so was suprised to see such narrow tires.

On the illustrated crossmember; I do not like that the left and right side LCA pivot points do not appear connected. They hang down and can flex sideways in corners. If that is the case it will be like the 30's/40's Ford beam front suspension with transverse spring.

 

[J-c-c]

On the illustrated crossmember; I do not like that the left and right side LCA pivot points do not appear connected. They hang down and can flex sideways in corners. If that is the case it will be like the 30's/40's Ford beam front suspension with transverse spring.

That is I agree an obvious area that would benefit from a tie bar, just need to resolve the oil pan issue or upgrade to dry sump?

 

[Kern Dog]

That setup in the yellow car look light duty, like something someone in Cuba built just to have something when the car was bought stripped out and missing a bunch of parts.

 

[junkyardhero]

That setup in the yellow car look light duty, like something someone in Cuba built just to have something when the car was bought stripped out and missing a bunch of parts.

true, that does look a little wanting for girth.

at least it's not also supporting the weight of the engine as well. perhaps because it's got that motor plate, that's an indication of it being a drag only car?

 

[racerjoe]

1st: Generally made out of cut plate and square tubing at right angles with no gussets or triangulation whatsoever. This might be just fine for a drag only car and possibly a street car but there's nothing stopping any of these from parallelagraming other than the wall thickness which has a minor effect. The entire car does this to some extent also but not having the OEM k-frame in my opinion makes this more likely. The OEM K-shape is much better for this and it also has vertical height in the middle which would resist bending and torsion. The sway bar mounts like this have to just be flexing left and right since they are basically on horns sticking out. It's a real area that can be improved. Another tie bar in front back to the rails of the k-frame, gussets, smaller square tubing with triangulation would make a serious difference.

So far on this thread I have not commented on how much stiffer the car feels with the HDK. I'm sure most will call BS or say it's psychological, but the car feels stiffer with the HDK. Based on the commentary, perhaps I'm the only that has gone from a well built t-bar setup to the HDK for a real world comparison, so I'll understand the skepticism. After the HDK install, a friend that goes to Moparty with me every year even commented on how much stiffer and more responsive the car felt and he was a passenger. This was before any the geometry adjustments. Agreed there is no triangulation on the K and there may be some concerns of paralleling, but I don't feel it.
Sway bar mounts- the picture you shared must be the old HDK design since mine are different. The brackets are made with vertical triangulation for stiffness. You mentioned left to right stiffness on the sway bar bracket. I'm sorry, but if your sway bar is moving left to right any significant amount, you have a problem. The bar itself is meant to float in the bushings, which is likely fractions of an inch. I've never seen witness marks on the bar where it moved outside the width of the bushing.

2nd is the LCA with the narrow pitch of the two pivot points. Generally, you want is further apart for stability as you find in nearly all modern cars but how to totally solve this using a front steer rack and such a low pivot point, I am not sure. You'd almost need to go with a strut rod that would ride above the tie rods but this might not be possible. In an original Mustang II / Pinto the strut rod goes to the rear direction but on an A-body it wouldn't have much support even if there was a pickup point due to the location of the k-frame bolts without welding something to the stock frame rails. The pivot points being low is also inviting more flex to the k-frame and movement under load.

I'm not sure I understand what you mean "narrow pinch of two pivot points".

I realize some people do not like the idea of single shear design. I can't change anyone's opinion on that. The shaft for the LCAs is machined .75" steel (don't know what type) with a nice radius at the corners of steps where the threads are. This shaft has a very neat fit into the tube on the K. The shaft doesn't rotate, the delrin bushings rotate on the shaft. I believe all the steel tubing used is chromoly, Denny can chime in on this. These LCAs aren't bending! I don't see the need in a strut rod when there are already two mounting points for the LCA. I've never seen any other high end aftermarket front suspensions or even factory designs using strut rods on wishbone LCAs.

 

[racerjoe]

Did you figure out the tire size limitation on the front from the K-frame? It was quite easy to put the 275-35-18s in the car in my case with the stock stuff, so was suprised to see such narrow tires.

Forgot to address this one in my previous post.

I've been running an 8" wide wheel with a 235 since I put the car back on the road with T-bar setup. I'm sure you know how hard it is to find an off the shelf wheel with the proper backspacing (for the front and back). I was wanting a 9" wheel for the front, but the ones I have weren't available with the proper backspace. There are no limitations to running a 9" wheel on the front. In fact, I'm planning on having these wheels widened to 9" so I can run a 275 tire. The tire will contact the frame rail before the tie rod contacts the wheel.
In reality, the adjustable LCAs would make it easier to source wheels since you would be able to pull the hub in, negating the need for a 6.5" backspace wheel.

 

[racerjoe]

I'll have to look it up. This pic is one test I ran. I calculated an amount of inward force the k member might see on the upper shock/springs mounts, ignoring any contribution the body might provide when bolted together, as before and after was my goal. In this pic I believe you are seeing 425? lbs pulling both mounts straight inward as a portion of the force they will see with the angled springs, and measured movement before and after modification vs relaxed. The difference was not startling, but enough for me to justify the effort, and I suspect way more then say any LCA reinforcement will ever measure.

Sorry, I couldn't resist.

View attachment 1716196651

This is irrelevant data since it isn't bolted to a car. You're also pulling on shock towers that have been known to have some failure problems. HDK doesn't use this design.

 

[J-c-c]

This is irrelevant data since it isn't bolted to a car. You're also pulling on shock towers that have been known to have some failure problems. HDK doesn't use this design.

Excuse me?
The pictured test goal was comparing an unmodified unpictured RMS K frame to my modified RMS K frame pictured in #121. It's data, ignore it at your own risk.
You neglected to mention the shock towers you refer to are also the coil over towers.
Frankly, your comment here is at least, irrelevant.
I have yet to hear any verified reports of RMS shock/coil over tower failures. And sorry, the HDK does indeed use the RMS basic design, with minor changes, not all IMO exactly positive.
If you don't understand the previous meaning of "pinch" here used previously, you might want to remain on the sidelines a bit longer.

 

[racerjoe]

Excuse me?
The pictured test goal was comparing an unmodified unpictured RMS K frame to my modified RMS K frame pictured in #121. It's data, ignore it at your own risk.
You neglected to mention the shock towers you refer to are also the coil over towers.
Frankly, your comment here is at least, irrelevant.
I have yet to hear any verified reports of RMS shock/coil over tower failures. And sorry, the HDK does indeed use the RMS basic design, with minor changes, not all IMO exactly positive.
If you don't understand the previous meaning of "pinch" here used previously, you might want to remain on the sidelines a bit longer.

Calm down buddy. This thread isn't meant to be a pissing contest on which is better, worse, stronger, weaker, prettier, heavier, or whatever. You can find other threads to go flex on with that nonsense. I refuse to engage and turn this into anotherthread with the same repeated comments. This thread is intended to discuss real world handling characteristics and geometry improvements. Perhaps you can provide geometry measurements so we can all learn what various brands offer.

If you don't understand the previous meaning of "pinch" here used previously, you might want to remain on the sidelines a bit longer.

Thanks for your valiant effort in helping everyone learn. I'll be over here on the sidelines driving the **** out of my car and now worrying about how strong the coil over towers are.

 

[Kern Dog]

Just by appearance alone, this looks really flimsy.

The cantilevered sway bar connections look ripe for flex. The narrow space between LCA mounting points. The lack of shear resistance/parallelogramming due to the one single 2x2 connection between the two sides...
I've been wrong before but not yet today.

 

[racerjoe]

Just by appearance alone, this looks really flimsy.

View attachment 1716197334

The cantilevered sway bar connections look ripe for flex. The narrow space between LCA mounting points. The lack of shear resistance/parallelogramming due to the one single 2x2 connection between the two sides...
I've been wrong before but not yet today.

Please refer to comment 144.

 

[Kern Dog]

I read that. If you're happy, that is great.
It just doesn't look robust to me.

 

[Dale Davies]

That setup in the yellow car look light duty, like something someone in Cuba built just to have something when the car was bought stripped out and missing a bunch of parts.

Looks drag race light weight oriented to me. Cornering not a consideration.

 

[Kern Dog]

I can see that. For that, it seems right.
Again, I may be expecting too much after dealing with the strength and durability of the stock stuff.
I'm a retired Carpenter that worked most of my life building houses and schools up to Bay Area earthquake standards. What I was trained to build would be grossly OVERbuilt for Colorado, Texas or Michigan. I'm talking thicker lumber, more reinforcements, blocking, metal straps, everything possible. THEN I retired and helped a few times on remodel work for friends and was shocked at how poorly built some 50-100 year old houses are...yet they are still standing today despite lacking the very reinforcements I thought were necessary.
This has led to some "questioning" of methods and procedures I've followed with other things.
Don't use drugs, you'll get hooked.
Don't have unprotected sex, you'll get her pregnant the first time.

My point?
Maybe I've been led to believe that we needed all that extra mass just to hold it all together but maybe it could have been revised to cut weight without being detrimental to durability.

 

[Dale Davies]

I can see that. For that, it seems right.
Again, I may be expecting too much after dealing with the strength and durability of the stock stuff.
I'm a retired Carpenter that worked most of my life building houses and schools up to Bay Area earthquake standards. What I was trained to build would be grossly OVERbuilt for Colorado, Texas or Michigan. I'm talking thicker lumber, more reinforcements, blocking, metal straps, everything possible. THEN I retired and helped a few times on remodel work for friends and was shocked at how poorly built some 50-100 year old houses are...yet they are still standing today despite lacking the very reinforcements I thought were necessary.
This has led to some "questioning" of methods and procedures I've followed with other things.
Don't use drugs, you'll get hooked.
Don't have unprotected sex, you'll get her pregnant the first time.

View attachment 1716197353


My point?
Maybe I've been led to believe that we needed all that extra mass just to hold it all together but maybe it could have been revised to cut weight without being detrimental to durability.

Intended use. To haul a big trailer, you could use a small block built to big block power, but it will not last as long. There is a good reason that large industrial engines have cylinder block castings 1" or more thick. It is to withstand vibrations and flex that is imposed while running at 100% power for 24/7 for months at a time.
Clownyfornicatia has a tendency to go overboard when a disaster occurs, such as earth quakes. Now the old homes may not have been subjected to the extreme ground displacements for one reason or another. Codes were changed so that during new construction and remodels, homes would be strengthened to prevent total collapse.
In a race car where weight is generally a penalty, they are built light. Colin Chapman, founder of Lotus Cars removed weight wherever he could until a failure occured wherein he added a bit of strengthening. The original Lotus Seven was only 950 pounds. These early chassis had a propensity to crack just behind the seats. Later cars added about 75 pounds. Chaterham worked for Lotus Cars and bought the rights when Chapman ceased production of the Seven. He beefed up the chassis more and installed larger and torquier engines under Chaterham Cars. These generally are between 1150# and 1250# and have had up to 310HP 2.0l Duratec engines installed.