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

[DionR]

Character building.

You should see what he said before he edited it.

 

[racerjoe]

I didn't say it didn't have anything to do with handling, I just said it had A LOT to do with horsepower. Because if you can't get up to 70 in that space you're going to lose a ton of time. And if you can't get going fast enough then turning the corner isn't as big of an issue.

Yes, you need to have decent handling to make the corner, but if you don't have the horsepower or the brakes it won't be a win. The 3S does challenge the whole car, but, it's a very horsepower dependent event.



Yeah I don't know that I'll be making Moparty any time soon. I'd need more than a week to make that a viable trip. I love driving my car but I'd hate to show up and feel like I was out of it because I wasn't in the HP ballpark.



I'll have to refresh my memory, I thought you ended up with more than that into it! That wouldn't be bad.



Thanks for sharing your thoughts!

You're still running the factory LCA's correct? With 1.08's that would definitely limit your ability to lower the car.

The QA1 tubular LCA's give almost a full inch of additional travel clearance, so on my car with 1.12's running lower isn't a big issue. I occasionally bottom the suspension, but it's fairly infrequent. My issue now is that at full compression my wheel kisses the top of the inner fender, so I'm body limited not suspension limited. My Doug's D453's are only 3.5" off the ground at the flange, so I can't go much lower anyway before the exhaust bottoms out before the suspension does. I probably only have about 1" or maybe less of clearance there at full compression.

The '73/74 B-body LCA conversion that Firm Feel used to sell gives even more compression travel than the QA1 tubular LCA's, but because of the exhaust and inner fender those would have to be dialed back with a taller bumpstop.

The new Falken's are very impressive, with my old 615k's I wasn't getting any rubbing in the back with my 1/2" spring offset and 295/40/18's. Now with a new set of RT660's I'm getting a bit of rubbing on the inner wheel well again. I moved a step stiffer on my Hellwig rear sway bar, but I'm still getting a touch of rubbing when I'm pushing through the mountain roads on the way home with the trunk full from my Costco trip.

"Yes, you need to have decent handling to make the corner, but if you don't have the horsepower or the brakes it won't be a win. The 3S does challenge the whole car, but, it's a very horsepower dependent event."


Well I came in 4th in the 3S and was .45 seconds from first. I was faster than the 3 dudes in front of me in the 1/4. It's not all HP in the 3S. I do think I could have overcome that time difference with more runs but I was really not wanting to make my front tires square. Therefore, I was doing alot of brake pedal modulation and stopping very early since I was giving myself extra space to account for the modulation.

 

[DionR]

Well I came in 4th in the 3S and was .45 seconds from first. I was faster than the 3 dudes in front of me in the 1/4. It's not all HP in the 3S. I do think I could have overcome that time difference with more runs but I was really not wanting to make my front tires square. Therefore, I was doing alot of brake pedal modulation and stopping very early since I was giving myself extra space to account for the modulation.

What cars finished ahead of you? Curious if they were late model cars with ABS.

 

[racerjoe]

What cars finished ahead of you?

Mitch- Challenger, Steve- Charger, David - Superbee

 

[TT5.9mag]

You should see what he said before he edited it.

I did and that’s what I responded to. I tried like hell to get it to quote but it wouldn’t. He redacted too quick.

 

[DionR]

I did and that’s what I responded to. I tried like hell to get it to quote but it wouldn’t. He redacted too quick.

I intentionally left it alone. I figured he would edit it and waited to see what he said after he came down a little.

 

[HemiDenny]

yeah...I'm the talker.

here is a partial current list..........

currently finishing up a Hellcat swap in a 69 RoadRunner for a local guy which involved major rust repair before the swap could even begin

also swapping out the fuel injected small block / Passon 5-speed in my buddy's Dart for a big arm fuel injected Hemi / automatic

working on the new Butch Leal 6.4 Hemi / 6 speed build that is on the fab table

rebuilding and 50/50 partner (I'm doing all the work) on a recently purchased 68 GTX / 4-speed / Dana

still doing several K packages a week along with a half dozen coil over conversion a month....I talk to each customer, pre-assemble....and ship by myself.

pretty much on my own, doing all the electrical, HVAC, and interior insulation on my almost complete 5400 sq ft shop.

Oh.....I almost forgot, in the last 6 months I buried my 2 older brothers (and my mother in law) and guess who is the executor of my brothers estates?, And who got to clean out their houses, and get their affairs in order........you guessed it, me. I really wanted to be at MoParty but I am fortunate to make a daily trip to take care of my 95 year old dad


And you are correct, I do not need the money, I just like staying creative. The view I see from 10,000 ft is I got a pretty full plate for my age (70).....but YOU clowns think I should build an AutoX car to please you?.....you got to be shitting me!.

 

[HemiDenny]

Ill add it back in for you (and anyone else)....you are a complete f*uckin idiot.

 

[JBrian]

Yeah I really should have ridden with one of y’all. Maybe next year I’ll have shrunk a little with age to where I can fit in your passenger seat.

Caleb, Next year, I'll take the sound system out and lower the passenger seat. Just watch my perfect headliner dude, you're like a foot taller than me!!!

 

[NC Engine Builder]

Ill add it back in for you (and anyone else)....you are a complete f*uckin idiot.

"Classy"

 

[TT5.9mag]

he came down a little.

Apparently that didn’t happen.

 

[HemiDenny]

there comes a time you got to call it as you see it.....if anyones candy-*** can't handle a little rough language....maybe you better stay on the porch.

 

[NC Engine Builder]

there comes a time you got to call it as you see it.....if anyones candy-*** can't handle a little rough language....maybe you better stay on the porch.

Isn't it ironic, YOU cant seem to deal with it when pressed or questioned on anything, so you get frustrated and respond with emotion and anger.

 

[HemiDenny]

"Classy"

after your rants.....give me a break

 

[toolmanmike]

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 get the feeling this will get messy.

Second post and the predictions were right. Looks like we need to back up and take a breath.

 

[NC Engine Builder]

after your rants.....give me a break

Rants? That funny. You know, as a fellow professional who works for the public, let me give you some free advice. If you are selling something or doing work for the public, you should EXPECT people to question your products/services, and it sometimes requires quite a thick skin. You seem to be taking people with questions as some sort of personal insult, but relax, that's not the case.

 

[DionR]

yeah...I'm the talker.

here is a partial current list..........

currently finishing up a Hellcat swap in a 69 RoadRunner for a local guy which involved major rust repair before the swap could even begin

also swapping out the fuel injected small block / Passon 5-speed in my buddy's Dart for a big arm fuel injected Hemi / automatic

working on the new Butch Leal 6.4 Hemi / 6 speed build that is on the fab table

rebuilding and 50/50 partner (I'm doing all the work) on a recently purchased 68 GTX / 4-speed / Dana

still doing several K packages a week along with a half dozen coil over conversion a month....I talk to each customer, pre-assemble....and ship by myself.

pretty much on my own, doing all the electrical, HVAC, and interior insulation on my almost complete 5400 sq ft shop.

Oh.....I almost forgot, in the last 6 months I buried my 2 older brothers (and my mother in law) and guess who is the executor of my brothers estates?, And who got to clean out their houses, and get their affairs in order........you guessed it, me. I really wanted to be at MoParty but I am fortunate to make a daily trip to take care of my 95 year old dad


And you are correct, I do not need the money, I just like staying creative. The view I see from 10,000 ft is I got a pretty full plate for my age (70).....but YOU clowns think I should build an AutoX car to please you?.....you got to be shitting me!.

You're the one accusing anyone that disagrees with you of being talkers since we aren't out racing. We are all busy doing stuff, losing people and taking care of things other than cars. Priorities and life make us all make choices. But you seem to want to project on anyone on the other side of the fence that if they aren't on an autox course they are just talkers while that can't be applied to you. If it applies, it applies to all.

I could care less if you build an autox car. Just suggesting that if I am a railbird, so are you and suggested a path for you to travel to change that. And since we are talking about handling, that seems the logical path.

 

[TT5.9mag]

we need to back up and take a breath.

We?

 

[junkyardhero]

We?

the royal we, michael. the... editorial we, as it were.

 

[HemiDenny]

Rants? That funny. You know, as a fellow professional who works for the public, let me give you some free advice. If you are selling something or doing work for the public, you should EXPECT people to question your products/services, and it sometimes requires quite a thick skin. You seem to be taking people with questions as some sort of personal insult, but relax, that's not the case.

questions?....bullshit.

that asshole said I know nothing about suspension geometry basically saying the reason why I teamed with Tim was to have him work it out for me.
posted my product isn't durable.....but nothing to back it up.
posted not proven while I been at it for more than 2 decades....no breakage, no issues.

guys luv to dish it out but when I call BS and give it back....then I'm the bad guy? I stand by my record, they can pound sand..

 

[toolmanmike]

We?

"You" points fingers unless I name names, and people that aren't involved get all bent out of shape. I am not going to read through 27 pages to see where all this started and who started it.

 

[NC Engine Builder]

questions?....bullshit.

that asshole said I know nothing about suspension geometry basically saying the reason why I teamed with Tim was to have him work it out for me.
posted my product isn't durable.....but nothing to back it up.
posted not proven while I been at it for more than 2 decades....no breakage, no issues.

guys luv to dish it out but when I call BS and give it back....then I'm the bad guy? I stand by my record, they can pound sand..

Just keep doing what your doing, you DO have a nice product. Dont take it all so personally. Maybe take a little break or something.

 

[RustyRatRod]

With all of this, I can completely see where someone might get frustrated and just give up product production and say to hell with it. Why can't yall just agree to disagree and leave it there? I'm just glad someone offers something aftermarket that actually works and is available for MOPARS. Why not just look at it like that, regardless of whether you're going to use it or not?

 

[DionR]

that asshole said I know nothing about suspension geometry basically saying the reason why I teamed with Tim was to have him work it out for me.

Ah, that's the crux of it this time.

Let me explain why I have the opinion that suspension geometry isn't "your thing".

1. Deflections when discussing your suspension geometry and if it was "improved' over the stock A-Body suspension. You state (and correctly so) that you never made claims that the geometry was better. Leaves the impression you really don't know what the geometry looked like at all.

2. Comments about roll center and such are never responded to. Only attacks or ignored. Zero discussion on geometry from you.

3. Suggests to build a handling car are (generally) responded with "I just like hanging with my buddies" suggesting that how a car handles isn't on your radar.

I could go back and quote you but too much time wasted to do that. And there might even be other reasons beyond the above that I might remember if I went back, but that's pointless.

Based on those things, I came to the conclusion that I did. If I am wrong, I am open to be schooled.

The comment that you co-opted Tim was maybe overly pointed. But you have to admit that it's not completely untrue. You already admitted you have enough on your plate so developing the kit for handling wasn't going to work for you to do it yourself. So you went looking for someone that would work it over and improve the design, which Tim did. You even said you hand picked him for that reason. Effectively, what Tim has under his car now isn't any of your design beyond the general layout, only the rack is in the same location as far as I know. It was a savvy move, you get a better handling kit to offer and exposure in a market you didn't really have much in before.

posted my product isn't durable.....but nothing to back it up.
posted not proven while I been at it for more than 2 decades....no breakage, no issues.

I don't ever remember saying I thought it wasn't durable. Plenty have, but all I have pointed out is the loading on the frame rails and some concerns for the rigidity of the system. I don't remember once saying durability was an issue.

But now that you mention it, I wonder if your k-frame would fold in and not allow a body to be dropped over the motor like a guy on here recently had with a Hellcat and an RMS kit. He had to jack the k-frame apart to get it past the frame rails. I haven't posted a comment about that here just to leave things alone, but feels pertinent to this comment now.

But saying I think the thing is going to fall out of the car and kill someone...that was someone else.

But I get it, I pissed you off. You reacted.

And if I didn't have anything to back it up with, why does what I say matter anyways?

 

[HemiDenny]

Hell, I ain't going anywhere, I do this for fun and to get out of the house. Not surprisingly, I been around the woulda / coulda railbirds all my life. Hasn't bothered me yet, I sure ain't gonna loose sleep over the "also rans"