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

[72bluNblu]

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.

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.

The problem is that when you start talking about things that are entirely subjective you open the conversation to opposing opinions. Saying the HDK "feels stiffer" is 100% subjective. And without some kind of analysis of the torsional resistance of the HDK, or the amount of flex in the chassis with an HDK mounted, it will remain 100% subjective.

Same goes for handling. Saying the car feels better is fine, but again that's entirely subjective. My personal opinion is that 90% of the "feels better" comments that come from installing a coil over conversion boil down to 3 things- the feel of the rack and pinion (which adds no performance), higher wheel rates than what was previously run on the torsion bar suspension, and better shocks. The latter two are easily addressed now with the torsion bar and shocks options available.

I've never heard of an RMS AlterK or a HDK with an actual structural failure. That said, the lack of a few simple gussets is surprising to me, and that goes for ALL of the coil over K's, not just the HDK. There was a tubular style K member available through DC for the circuit cars, and it had gussets. I'm still researching its actual construction, but it appears to have had a lot more reinforcement than any of the currently available coil over conversions. The application of course is something to consider.

What I would really like to see is a full plot of the toe change, camber change and roll center, like what Bill Reilly did in his "debated usage" article for the FMJ spindles. Now, that suspension was basically entirely stock except for the 1" lower ride height compared to factory. It was run with 26" tires and a rake of 1.5", which of course changes some things. We've now seen some of the camber gain numbers, but that's only part of the puzzle and @racerjoe showed that in the stock HDK configuration with 1" extended ball joints and his cars setting the camber gain on the HDK was substantially worse than the basically factory stuff here. Which he fixed with a 2" extended ball joint to get slightly better numbers than a basically stock torsion bar suspension.

Obviously the ride height makes a big difference because it changes the control arm angles. In the case of the HDK, the LCA length also has the potential to make some significant changes toward the roll center and the toe change, because changing the length of that control arm changes both the angle of the control arm AND the arc it will travel in.

Ultimately my goal is to make a plot like this for my car, because it's flatter and lower stance and adjustable UCA's will change some of the values compared to the article numbers. Probably not as much as changing the length of the LCA by a 1/2" like you can do with the HDK, but I don't have the numbers yet so that's easy to say. It's going to be a bit though because I'll need my shop finished before I can attempt it.

 

[davescuda]

If you have not seen a HDK set up in person. I think you will be surprised.

 

[72bluNblu]

If you have not seen a HDK set up in person. I think you will be surprised.

By what?

It's welded rectangular tubing, that's not all that exotic and I've seen lots of that. And gusseting is easily seen in pictures. I would expect the wall thickness to be substantially higher than what the factory K's have, to make up for the loss in cross sectional area vs the factory K.

I'm sure they're well made, I've never said they aren't. That goes along with all the happy customers and lack of documented failures. But that doesn't mean the strength questions are invalid either. Unfortunately I don't think anyone is doing an FEA of the factory components or any of the coil over conversions, so objective comparisons aren't going to happen.

 

[racerjoe]

Saying the HDK "feels stiffer" is 100% subjective.

Of course it is because there is no measurable value for human perception. However, as previously mentioned, my passenger who has been in the car for many miles commented that it "felt better". He was simply a passenger with only his *** being the connecting point to the car, no steering feedback in his hands. I wish I could explain it, but I can't. The only thing I can offer is a passenger seat for you to feel on your own.

higher wheel rates than what was previously run on the torsion bar suspension, and better shocks.

I originally had springs of similar wheel rate to my 1.08 bars. Are the QA1 shocks better than the Fox Hotckis? Sure the double adjustable makes it more versitile, but is there damping actually better? Likely another subjective comment unless someone has compared the two on a shock dyno.

I've never heard of an RMS AlterK

Likely my mistake. I've seen photos of fractured shock towers. Perhaps it was another brand.

What I would really like to see is a full plot of the toe change, camber change and roll center,

I'll see what I can do about the toe change and camber change through suspension travel. That will take some time to measure. I also need to educate myself on the proper way to measure toe change with simple tools. I think the best way to see the roll center change would be to use the online tool.

 

[davescuda]

I dont know enough to say anything that you guys are getting in deep here. I am not comparing it to any buddies else’s or to factory. I just think it’s well-made and it’s not wimpy. Plus it serves a big purpose when you’re doing customization work. Plus I am sure if all of you come up with some improvement on his design, I am sure he’d be more than willing to upgrade and to make it better, that he has already been doing over the years. Denny can correct me here but I believe this all started to put Gen 2 Hemi’s in A bodies.

 

[J-c-c]

By what?

It's welded rectangular tubing, that's not all that exotic and I've seen lots of that. And gusseting is easily seen in pictures. I would expect the wall thickness to be substantially higher than what the factory K's have, to make up for the loss in cross sectional area vs the factory K.

I'm sure they're well made, I've never said they aren't. That goes along with all the happy customers and lack of documented failures. But that doesn't mean the strength questions are invalid either. Unfortunately I don't think anyone is doing an FEA of the factory components or any of the coil over conversions, so objective comparisons aren't going to happen.

As mentioned earlier, wall thickness is not a real efficient path to gain stiffness, and I personally doubt it is much thicker, since weight savings is such a sales pitch that persuades the most customers.

 

[J-c-c]

Calm down buddy. Maybe you should have just asked the simple question in this context like "how is this "whatever" relevant?" before you start you start making declarations This thread isn't meant to be a pissing contest on which is better, worse, stronger, weaker, prettier, heavier, or whatever. You are the self-appointed decider what this thread is about now? You can find other threads to go flex on with that nonsense. We both can, I refuse to engage Like when? and turn this into another thread 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. Perhaps.

Thanks for your valiant effort in helping everyone learn. No problem 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. You obviously missed the point, again, Stay on the side limes, please. The inward pull in my test is primarily resisted by the K member that the shock/coil over towers connect to. It was mentioned that the towers have seen failures, and that is still news to me

 

[abodyjoe]

and this thread ends up just like the other thousand on this subject. lol

 

[72bluNblu]

Of course it is because there is no measurable value for human perception. However, as previously mentioned, my passenger who has been in the car for many miles commented that it "felt better". He was simply a passenger with only his *** being the connecting point to the car, no steering feedback in his hands. I wish I could explain it, but I can't. The only thing I can offer is a passenger seat for you to feel on your own.

I get what you're saying, and I understand. But when you say stuff like that, you open the door for directly opposing opinions. Which is also fine, but you have to understand you haven't "proven" anything by saying that, so we just end up going back and forth. I've had a life long "mopar guy" ride shotgun in my Duster and say it was the best handling Mopar he'd ever ridden in. I was super stoked to hear it and it meant a lot to me, but I'm not gonna say I have the "best handling mopar" because I know that's not true either.

I originally had springs of similar wheel rate to my 1.08 bars. Are the QA1 shocks better than the Fox Hotckis? Sure the double adjustable makes it more versitile, but is there damping actually better? Likely another subjective comment unless someone has compared the two on a shock dyno.

It was a general comment. Your 1.08" bars have an almost identical wheel rate as your 400# bars, assuming the motion ratio you supplied is decent (which I'm sure it is). I don't have a direct comparison on the shocks, the double adjustability I think would go a long way to improving feel because you can tailor it to what you like personally. That doesn't necessarily mean they'd make the car faster, but it adds to the "feels better" aspect of it.

Likely my mistake. I've seen photos of fractured shock towers. Perhaps it was another brand.

Gerst. There are multiple pictures of fractured uprights on the original Gerst K frames, before the design was bought out and improved by QA1. I'm not personally aware of any AlterK failures, although that doesn't necessarily mean there aren't any.

I'll see what I can do about the toe change and camber change through suspension travel. That will take some time to measure. I also need to educate myself on the proper way to measure toe change with simple tools. I think the best way to see the roll center change would be to use the online tool.

Oh believe me I know it takes some time and set up, it's why I haven't done it yet. There are a few different articles and books on how to do it with pretty simple tools, one of the "green brick" articles detailed how to do a lot of it with pretty simple stuff. I'll take a look at that article and see if it's as relevant as I recall.

I dont know enough to say anything that you guys are getting in deep here. I am not comparing it to any buddies else’s or to factory. I just think it’s well-made and it’s not wimpy. Plus it serves a big purpose when you’re doing customization work. Plus I am sure if all of you come up with some improvement on his design, I am sure he’d be more than willing to upgrade and to make it better, that he has already been doing over the years. Denny can correct me here but I believe this all started to put Gen 2 Hemi’s in A bodies.

Absolutely getting into the weeds on some of this. But really that's the only place you can make some of these comparisons objectively.

Because realistically, we're almost always going to be comparing different cars with different drivers, even when we can use the same track. Tim's comparison is one of the few that actually compares a pretty well tuned torsion bar suspension against a pretty well tuned coil over conversion, but even then we're still comparing a lot of subjective elements. Even just Tim progressing as a driver (which is awesome) will mean that his times will get faster as he goes along, so just saying he ran a certain track faster now than before isn't 100% on the suspension change.

@J-c-c

Maybe you should have just asked the simple question in this context like "how is this "whatever" relevant?" before you start you start making declarations.

You are the self-appointed decider what this thread is about now?

You obviously missed the point, again, Stay on the side limes, please. The inward pull in my test is primarily resisted by the K member that the shock/coil over towers connect to. It was mentioned that the towers have seen failures, and that is still news to me

This is uncalled for. This is Tim's thread, and while I would like to see additional geometry measurements comments like these just serve to derail the thread from any objective findings. Tim knows more than enough to not "stay on the side lines", he's already done more to measure and post geometry comparisons for the HDK or any coil over conversion that I've seen.

 

[racerjoe]

but I'm not gonna say I have the "best handling mopar" because I know that's not true either.

I'm definitely not trying to portray this image! I'm just a dude trying to be slightly better than average and have a good time doing it. I also like to learn new things and help other people learn from my experiences.

This is uncalled for. This is Tim's thread, and while I would like to see additional geometry measurements comments like these just serve to derail the thread from any objective findings. Tim knows more than enough to not "stay on the side lines", he's already done more to measure and post geometry comparisons for the HDK or any coil over conversion that I've seen.

It's best to ignore these guys...

 

[goldduster318]

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.

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.

View attachment 1716197230

I point it out because without knowing literally ALL details, modeling it, doing an FEA, or some flex test we're basically talking standard textbook engineering stuff.

If you take two parallel members, connect them with one crossmemeber welded at a 90 degree angle with no gussets, when you put a load on this (remember it has a big moment arm from the wheels and also the lower control arms are not between the mounting points on the vehicle) as shown below and it parallelagrams on a level that you probably can't see with your eye, and this also happens to a lesser extent to the entire chassis (which is why also triangulation as simple as the 73+ struts from the firewall to the fender supports helps enough that I could also feel it in the wheel on my torsion bar car). The tie bar you show will help somewhat IF and only if its not a rod end and it has no bushings. In a quick search, I couldn't find a good enough picture to determine which type it is. If it's anything but fully rigid it likely does a'most nothing. It's going to be minor against parallelagraming because again there's no triangulation.

In addition, looking from the front of the car, you have an induced torisional moment into the tube which is made worse by the lever arm below the k-frame. So only the wall thickness reduces it because you generally have one bolt and mounting point with this lever arm and it's not spread out across the entire support frame in the way it would ideally be. This is my point with the narrow pivots.

For an example, I own a 2004 Chevrolet Colorado ZQ8 truck (was replacing the wheel bearing here but this is the best shot) which is further lowered using adjustable coilovers, this has a front steer rack, SLA suspension, front mount sway bar and a coil over shock with a tower from the factory that does not turn, so generally the suspension design in the HDK / Alter-K / QA1 kits, but in a factory design setting. You can see the front and rear pivot points for the LCA which takes all the load are as far apart as possible. This spreads the load out, reduces dynamic flex, and provides better tracking overall. Each side is mounted with a double shear. The strut rod in the stock system is the second pivot point and it's controlling for-aft movement due to the triangulation as well as side to side and the moment. This design is basically if the metal is flexing under the moment it is what it is.

My own feeling having driven that vehicle over 100k miles vs my Duster with 1.06 T-bars, hotchkis non-adjustable shocks, etc is the on-center feel is better mostly due to the front steer rack and pinion, despite having more body roll than my Duster. I think the limits are lower, but it objectively feels slightly better at anything that isn't right at the limit. This truck also has the ball joint type sway bar end links which are more responsive feeling because there is zero flex.

Regardint the sway bar, there is never a perfect side load, it's always a tension load up/down on those points so it's unlikely it slides at all. But there is a load with an angle and that design will be under bending and torsion as a result of it being unsupported. It just seems like they would be flexing all over the place. The design in the Alter-K is different and IMO better in this area. So you end up with a torison moment around the cross car axis and bending with an angle relative to vertical with fairly minor support. Also in nearly equal and opposite directions when mirrored across the car centerline

Just for a comparison sake of what's out there, this is a Maximum Motorsports K-frame for a Fox Mustang. You'll notice it has one crossmember on the front, the cars are front steer rack, though they are strut, but it does have an A-arm. You can see they have triangulation tubes and gusseting in several directions and a tie bar that is solid that mounts between the rear body attachment points. It also has a much wider and double shear pattern for the lower control arm mounting and as far as I'm aware this has quite heavy wall thickness. The rack is mounted directly to the cross tube and the triangulation is nearly right at the mount. This is about as good as you can do given somewhat similar constraints.

I would say also if you want to talk about things being flimsy and not falling apart, the fox mustang, especially the convertibles is a fantastic example of something that has the chassis stiffness of wet spaghetti stock but doesn't fall apart. Not breaking is a minimum requirement. On a small enough scale, the entire car is flexing.

Also please don't take this as criticizing the quality of any fabrication regarding the HDK / Alter-k-tion / QA1 because I don't view it as dangerous, but the engineering side of it leaves quite a bit on the table for a handling application, and I'd say it's quite good on a drag car. I mean you could literally make some of these improvments after the fact if you like (gussets, support bars, different sway bar mounting tab design). Anything is possible.

The stock K-shape is just better in torsion at bending because the K is making its own triangulation in one direction and it's a large cross section box tube in the other direction.

 

[J-c-c]

JCC:
Maybe you should have just asked the simple question in this context like "how is this "whatever" relevant?" before you start you start making declarations.

You are the self-appointed decider what this thread is about now?

You obviously missed the point, again, Stay on the side limes, please. The inward pull in my test is primarily resisted by the K member that the shock/coil over towers connect to. It was mentioned that the towers have seen failures, and that is still news to me

72Blu: "This is uncalled for. This is Tim's thread, and while I would like to see additional geometry measurements comments like these just serve to derail the thread from any objective findings. Tim knows more than enough to not "stay on the side lines", he's already done more to measure and post geometry comparisons for the HDK or any coil over conversion that I've seen."

So according to you, it promotes a discussion when an OP states categorically another's comment is "irrelevant" and offers no foundation whatsoever, and can't be bothered to even ask why it might be considered "irrelevant" because their understanding of the matter at hand might be limited, and that doesn't serve to derail a thread, have I got this right?

I'm just trying to wrap my head around how PC these threads need to be so as to protect any feathers from being ruffled, and taking figuratively baby steps in that regard.

 

[J-c-c]

I'm definitely not trying to portray this image! I'm just a dude trying to be slightly better than average and have a good time doing it. I also like to learn new things and help other people learn from my experiences.

It's best to ignore these guys...

A new concept for greater understanding, ignore what apparently confuses you?

 

[J-c-c]

This is the best Mopar aftermarket IFS rendition I have seen with my own eyes. It has a few details I would like to see addressed, and most are minor, and correctable given the will.
It checks a lot of boxes.
Morrison Chassis in Tacoma Washington

 

[HemiDenny]

Here is a fun fact regarding those OEM K frames. Know who Mopar sub-contracted the K frame build production to? Those wacky water heater guys in Kankakee, Illinois. The A.O. Smith Co. They aslo built silos.

While the stamped steel of the OEM K is likely where it's strength comes from, those stamped steel K's for the most part are only spot welded together....and have you examined some of those spot welds?? Must of had a few guys named Stevie and Ray heading the line. In all sincerity, I cannot remember anyone doing anything remotely competitive with an OEM K unless it received at minimum a full re-weld and likely additional reinforcement.

Hot Rodding 101....be a fan of adding needed strength, but never a fan of adding unnecessary weight.

 

[HemiDenny]

View attachment 1716197527
This is the best Mopar aftermarket IFS rendition I have seen with my own eyes. It has a few details I would like to see addressed, and most are minor, and correctable given the will.
It checks a lot of boxes.
Morrison Chassis in Tacoma Washington

I'm all ears...what in your opinion makes it so great???? I do luv the tall spindles. Kinda looks like their Chebbie set up, widened, with Alter K upper shock mounts.

 

[J-c-c]

I'm all ears...what in your opinion makes it so great???? I do luv the tall spindles. Kinda looks like their Chebbie set up, widened, with Alter K upper shock mounts.

Hold on, I never said it was great, I said "the best Mopar aftermarket IFS rendition I have seen with my own eyes".

Let me see what those not afraid to ignore me weigh in think first, so as not to taint the consensus.

And yes, those are effectively C6 uprights and a near copy of the RMS shock/cover tower.

 

[HemiDenny]

Hold on, I never said it was great, I said "the best Mopar aftermarket IFS rendition I have seen with my own eyes".

Let me see what those not afraid to ignore me weigh in think first, so as not to taint the consensus.

And yes, those are effectively C6 uprights and a near copy of the RMS shock/cover tower.

yeah....OK

 

[HemiDenny]

I point it out because without knowing literally ALL details, modeling it, doing an FEA, or some flex test we're basically talking standard textbook engineering stuff.

If you take two parallel members, connect them with one crossmemeber welded at a 90 degree angle with no gussets, when you put a load on this (remember it has a big moment arm from the wheels and also the lower control arms are not between the mounting points on the vehicle) as shown below and it parallelagrams on a level that you probably can't see with your eye, and this also happens to a lesser extent to the entire chassis (which is why also triangulation as simple as the 73+ struts from the firewall to the fender supports helps enough that I could also feel it in the wheel on my torsion bar car). The tie bar you show will help somewhat IF and only if its not a rod end and it has no bushings. In a quick search, I couldn't find a good enough picture to determine which type it is. If it's anything but fully rigid it likely does a'most nothing. It's going to be minor against parallelagraming because again there's no triangulation.

View attachment 1716197453

In addition, looking from the front of the car, you have an induced torisional moment into the tube which is made worse by the lever arm below the k-frame. So only the wall thickness reduces it because you generally have one bolt and mounting point with this lever arm and it's not spread out across the entire support frame in the way it would ideally be. This is my point with the narrow pivots.
View attachment 1716197456

View attachment 1716197457
For an example, I own a 2004 Chevrolet Colorado ZQ8 truck (was replacing the wheel bearing here but this is the best shot) which is further lowered using adjustable coilovers, this has a front steer rack, SLA suspension, front mount sway bar and a coil over shock with a tower from the factory that does not turn, so generally the suspension design in the HDK / Alter-K / QA1 kits, but in a factory design setting. You can see the front and rear pivot points for the LCA which takes all the load are as far apart as possible. This spreads the load out, reduces dynamic flex, and provides better tracking overall. Each side is mounted with a double shear. The strut rod in the stock system is the second pivot point and it's controlling for-aft movement due to the triangulation as well as side to side and the moment. This design is basically if the metal is flexing under the moment it is what it is.

My own feeling having driven that vehicle over 100k miles vs my Duster with 1.06 T-bars, hotchkis non-adjustable shocks, etc is the on-center feel is better mostly due to the front steer rack and pinion, despite having more body roll than my Duster. I think the limits are lower, but it objectively feels slightly better at anything that isn't right at the limit. This truck also has the ball joint type sway bar end links which are more responsive feeling because there is zero flex.

Regardint the sway bar, there is never a perfect side load, it's always a tension load up/down on those points so it's unlikely it slides at all. But there is a load with an angle and that design will be under bending and torsion as a result of it being unsupported. It just seems like they would be flexing all over the place. The design in the Alter-K is different and IMO better in this area. So you end up with a torison moment around the cross car axis and bending with an angle relative to vertical with fairly minor support. Also in nearly equal and opposite directions when mirrored across the car centerline
View attachment 1716197462

Just for a comparison sake of what's out there, this is a Maximum Motorsports K-frame for a Fox Mustang. You'll notice it has one crossmember on the front, the cars are front steer rack, though they are strut, but it does have an A-arm. You can see they have triangulation tubes and gusseting in several directions and a tie bar that is solid that mounts between the rear body attachment points. It also has a much wider and double shear pattern for the lower control arm mounting and as far as I'm aware this has quite heavy wall thickness. The rack is mounted directly to the cross tube and the triangulation is nearly right at the mount. This is about as good as you can do given somewhat similar constraints.
View attachment 1716197463

I would say also if you want to talk about things being flimsy and not falling apart, the fox mustang, especially the convertibles is a fantastic example of something that has the chassis stiffness of wet spaghetti stock but doesn't fall apart. Not breaking is a minimum requirement. On a small enough scale, the entire car is flexing.

Also please don't take this as criticizing the quality of any fabrication regarding the HDK / Alter-k-tion / QA1 because I don't view it as dangerous, but the engineering side of it leaves quite a bit on the table for a handling application, and I'd say it's quite good on a drag car. I mean you could literally make some of these improvments after the fact if you like (gussets, support bars, different sway bar mounting tab design). Anything is possible.

The stock K-shape is just better in torsion at bending because the K is making its own triangulation in one direction and it's a large cross section box tube in the other direction.

You gotta be kidding me...you could feel those firewall to fender braces in the 74 and up cars in the steering wheel? does NASA know about you?

BTW....Do you know why those (hint: mandated) braces were in there?

 

[Dale Davies]

Of course it is because there is no measurable value for human perception. However, as previously mentioned, my passenger who has been in the car for many miles commented that it "felt better". He was simply a passenger with only his *** being the connecting point to the car, no steering feedback in his hands. I wish I could explain it, but I can't. The only thing I can offer is a passenger seat for you to feel on your own.

I originally had springs of similar wheel rate to my 1.08 bars. Are the QA1 shocks better than the Fox Hotckis? Sure the double adjustable makes it more versitile, but is there damping actually better? Likely another subjective comment unless someone has compared the two on a shock dyno.

Likely my mistake. I've seen photos of fractured shock towers. Perhaps it was another brand.

I'll see what I can do about the toe change and camber change through suspension travel. That will take some time to measure. I also need to educate myself on the proper way to measure toe change with simple tools. I think the best way to see the roll center change would be to use the online tool.

Toe change is fairly simple. Remove the front springs. Put the wheels back on the front. Two pieces of plywood 2'×2' nailed to two pieces of 2×4 placed 1" from the tire with the LCA level to the floor. You can then raise and lower the wheel 1" at a time and plot the toe change. Check both sides to verify both are the same. You can then plot the height and toe on graph paper with left and right sides next to eachother but the + and - opposite. You get a good idea real quick of what is happening regarding toe change or as racers call "bump steer".
On a '48 Mercury truck I assisted on, the rack mounting was not done yet so we could C clamp the rack in a height we thought was appropriate. Then we tested the toe change. Then we moved the rack until we got the minimum toe change.
The inner rack tierod end pivot center should be along a line between the pivot center of the LCA and UCA. We found we needed a 1" spacer on each side, which was ordered. Once installed we retested toe change to verify. Once we were happy with that the rack mount could be welded to the cross member.

 

[racerjoe]

I'm all ears...what in your opinion makes it so great???? I do luv the tall spindles. Kinda looks like their Chebbie set up, widened, with Alter K upper shock mounts.

I actually looked for some cheap used vette spindles locally to take measurements. My biggest hurdle would be the upper ball joint since it’s mounted in the spindle. My thought was to have a ball joint “plug” made with a taper. That way the standard UCA could be used. Unfortunately, I don’t know any machinists and they would likely charge stupid money for a one off deal. I do think it would be a neat solution.

 

[goldduster318]

Here is a fun fact regarding those OEM K frames. Know who Mopar sub-contracted the K frame build production to? Those wacky water heater guys in Kankakee, Illinois. The A.O. Smith Co. They aslo built silos.

While the stamped steel of the OEM K is likely where it's strength comes from, those stamped steel K's for the most part are only spot welded together....and have you examined some of those spot welds?? Must of had a few guys named Stevie and Ray heading the line. In all sincerity, I cannot remember anyone doing anything remotely competitive with an OEM K unless it received at minimum a full re-weld and likely additional reinforcement.

Hot Rodding 101....be a fan of adding needed strength, but never a fan of adding unnecessary weight.

It doesn't matter what they built, I mean it's a metal stamping with some welding, they could literally have sent it to anyone who can meet quality standards. Honestly even those weren't very high, I agree on that. The general design of it is quite good though, especially considering using a slide rule and what else was out there that had existed before. It's clear they actually understood engineering principles.

The entire car is made with spot welds of varying quality. I can't remember ever seeing a picture of an OEM K-frame with popped spot welds. The welds at the pivot pin tubes, sure. The 3D shape in the vertical direction and the k shape in the horizontal direction is where the strength comes from but the stamping is basically free of ribs or darts otherwise. The brackets are somewhere between Billy Bob with a stick welder and Ray Charles welding it with his feet yet plenty of them are out there, I don't think the failure percentage is that high.

You gotta be kidding me...you could feel those firewall to fender braces in the 74 and up cars in the steering wheel? does NASA know about you?

BTW....Do you know why those (hint: mandated) braces were in there?

I've had this discussion with you before. I know you're going to say for crash impacts, yes it would help stiffen the part near the firewall that helps with crash which also means the front structure between the driver and the front suspension is stiffer. Which is postive for handling. You even see tying the firewall to the inner fenders / shock towers on things as early 1960 Falcons to the strut towers before there was even FMVSS or they cared at all about crashworthiness.

I adapted the braces to my own car and yes you can feel the difference, it's minor but there. Maybe you can't tell with stock 85 lb/in wheel rates but at 252 lb/in yes.

We have seen the spot welds actually pop between the firewall and the inner fenders with high spring rates. That area of the car flexes a lot because of no surprise to anyone who knows engineering having things at generally right angles isn't very stiff on its own and this triangulates the firewall to the inner fenders. This is preventing parallelagramming to some extent. They're strong enough you can shake the car back and forth and flex the suspension with them. You see a variation of this type of brace on basically everything once there was any care at all about chassis stiffness. The car companies are borderline fanatical about stiffening this exact area of the car in the same way now for better performance and NVH. And usually they're also called k-braces. I'm seeing a pattern here. Almost all newer BMWs, 2024 Mustang, and even the 2020+ explorer have similar braces. Our cars are made out of fairly light gauge sheet metal, they need all the help they can get for stiffness. The frame rails themselves are even quite light weight. It's not comparable to a modern fully boxed truck frame which may have similar cross section.

 

[racerjoe]

Hold on, I never said it was great, I said "the best Mopar aftermarket IFS rendition I have seen with my own eyes".

Let me see what those not afraid to ignore me weigh in think first, so as not to taint the consensus.

And yes, those are effectively C6 uprights and a near copy of the RMS shock/cover tower.

It’s funny how defensive you are getting.
My next comment will be from the street racing days - Where’s your car? Let’s line them up. I’ll be at Moparty in September. I don’t care if you’re on a Speed tech chassis with 335/ square with a redeye engine. Let’s see who’s faster around the cones. Lol.

FYI, openly insulting peoples’ intelligence is a reflection of yourself.

 

[J-c-c]

It’s funny how defensive you are getting.
My next comment will be from the street racing days - Where’s your car? Let’s line them up. I’ll be at Moparty in September. I don’t care if you’re on a Speed tech chassis with 335/ square with a redeye engine. Let’s see who’s faster around the cones. Lol.

FYI, openly insulting peoples’ intelligence is a reflection of yourself.

Oh Contraire, I'm mainly referring to the use of one's own words, and on that we agree, they are not often flattering, but they don't come from me.
I have no need to insult anybody, ever.
Sorry, I do reserve the right to defend myself at any time, I put a lot of effort in in trying not to escalate an insult, but that seems to be a rarity in these here parts.
Best antidote, don't say silly, stupid unsupported nonsense directed at others, and when you do, try not to double down when called out. It works for me I believe.
Now we have moved to "whose is bigger?"
Can we get back on topic now that I have tried to clear the air?

 

[go-fish]

RMS coilover towers WILL bend if you go in the ditch. That’s what it took for me to bend mine on my E-body. Bill Reilly told me to send it back and he’ll take care of it.

Sway bar mounts on the lca’s is solid on the RMS, HD looks to have the exact same mounting idea. There is no problem with the sway bar.

Strut rods on double a-arm suspension? Don't be silly.