What do you want in a tubular K-frame?

Hi guys,

I'm building a new K-member for a customers car and having Ron Sutton design all the suspension geometry to bring the car into the 21st century. My question is what would you guys like to see? I'm debating building these for more than just one customer. Would you rather have an OEM cartridge hub that is easily found and replaced or a more expensive tapered bearing hub? Remember a cartridge hub/spindle setup would be much cheaper, use current technology (think Speedtech AFX spindle) but your going to have to move to a 5-on-4-3/4 lug pattern. Is that a deal breaker? While this spindle and geometry would be light years ahead of anything currently available, it's not tailored specifically to the vehicle platform as a fabricated spindle and tapered bearing hub would be. This hub would allow the Mopar bolt pattern, a much higher bearing load capability, and the ability to have the geometry designed specifically for the cars specs (i.e. E-body, B-body), but at a significant cost increase. Not sure the cost is indicative of the performance gain, but you tell me.
Are you guys dead set on not cutting your aprons or modifying the upper control arm mounts?
Just trying to get a feel for everyones expectations.

What about an LX hub?

If doing a cartridge hub, need a spindle that is already available, and the Speedtech/ATS is about the best now and reasonable on cost. It accepts the ZR1 Corvette hub, which is larger and has a higher load rating than C5/C6 hubs.

What is the lesser of the evils? I guess if a guy is serious about it he could just redrill the hubs. Except for the square tire setup guys, running a 5x4.75 front wheel isnt that big of a stretch. What geometry changes are necessary to get a REAL advantage over the factory setup other than the spindle change?

Holy carp batman, at $480 a hub I am not sure you and I use the same definition of "reasonable on cost". Summit, Timken units.

Which leads me to think the whole kit and kaboodle will be too expensive to sell much of.

None of this stuff is cheap. ATS/Speedtech spindles with ZR1 hubs are going to be roughly $1300, while fabbed spindles and hubs are in the $2100 range. Considering this is one of the key components to modernize the suspension and elevate it to a true performance level, I don't feel like this is unaffordable. What I need to know is, do you? Lots of people have paid lots of money for the other two setups out there that are really nothing more than late 70's, early 80's tech. If this suits most peoples needs and driving styles, enough said. If however, your looking to be able to run your Mopar against the Speedtech, DSE, and all the other offerings for 1st and 2nd Gen Camaro's and everything else, then I think a need exist, however small! I am from the camp that thinks putting the lawn chair behind the car and parking it for several hours is not the best use or fun factor of these cars. I want to see them auto crossing or blasting through the twisty's! At the very least, not scare the bejesus out of you when you blast it down the highway and have to brake suddenly or change lanes!

I think what you are attempting to do is a good thing. What is currently out on the market seems to be, for me anyway and others WILL disagree, based on spindly Mustang II drag race applications that are sometimes used for road driving. I'm not sure how that stuff will last with thousands of load cycles on a car being driven on everyday highway/surface streets that in places live up to 3rd world standards. The stock stuff had no issues generally until it got driven like Dukes Of Hazard. How well does the current offerings put up with this kind of usage? Time will tell. As time goes on, the inventory of oe replacements is going to become non existent and we will be faced with having to go a/m. I would much rather go with something that has better geometry and replacement parts that can be easily sourced. Is your project going to be made out of dom mild steel or moly on the framing/arms etc? I know I would like to upgrade mine and will watch for more info from you.

At some point I would be interested in this type of system for one of my cars, will it be a full chassis or some kind of front clip?

Not sure what you are driving, but I haven't ever run into that as a problem on a highway that wasn't covered in snow or so much rain I was hydroplaning. And I've been known to blast past triple digits, Used to make the run From the Naval Station in San Diego to my folks house in 4.5 hours, that's a 400 mile drive. So it's not like I was driving Mrs Daisy here.

Not real sure what you mean by modernize the suspension, could you clarify what you mean by that?

Control arms will be DOM. Not a fan of CM for street use, as it does fatigue.

Niether, going to keep it as a bolt in K-frame.

Sounds like your good with the stock suspension, nothing wrong with that!

Modernized means KPI angles, camber curve, caster degree, scrub radius, and bump steer being optimized for control, handling, and braking....something the stock E and B bodies are seriously lacking, despite how fast you can drive to grandma's house.

I would guess that you will be looking at the E/B body front ends first or are you planning this for A body cars as well?

Well, I'm not an E or B body guy, so I may be missing something there. I owned a73 Challenger years ago, but it was well thumped when I got it.

Never had a B. Mostly A bodies and an occasional C. But I used to make my banzai runs in a G body, fwiw.

So that means an early decision in the design stage of usable wheel diameters, ie, no 15"'s, which really should not be much of a let down as they will soon become almost obsolete for street use in wide HP configurations?

Wheel diameter would be dictated by the brake package you chose, so 15" wheels would be possible, I think. Would have to check the spindle height, etc. I would not change anything to accommodate a 15" wheel, though. It either fits or doesn't! The more important aspect is the offset in relation to the width to have the correct scrub radius.

I have a customers stock E-body that all dimensions were measure from. I have access to B's and A bodies, just have to find the time to measure them up and see what changes would be necessary and more importantly, a paying customer for those!!

I would think with a front? steer rack and pinion, wide rims, and a decent scrub radius/KPI, anything smaller then 17" will not be doable. In my case, on this type of project, I would prefer better geometry over a 15" wheel look, which I am really fond of.

I'm pretty sure they won't fit. The spindle and steering is designed around an 18" wheel.

Well keep the post going on the system as you build it for the E body, are you planning on keeping the factory upper control arm mounts or will it have them on the new suspension?

That is one of the questions I was asking in the original post. Would having to move the original location be a deal breaker? Are you open to possibly even installing a new shock tower piece? I need to know what you guys would want and what your willing to do to have the best handling or are you willing to compromise handling to keep the original upper mount?

I'm thinking that if one was to spring for your setup that going all out would be the expectation. I can't see spending serious money for a new suspension that may be compromised by keeping the factory UCA mounts, assuming that would be a compromise.

I'm speaking only for myself here, if I was buying this kind of system which I ASSume will be in the $6000 range I would be looking for the best possible handling and not if I have to cut the car up or not. The market has enough products for stock suspension and enough bolt in Mustang II kits...so if you are going to do it make sure you don't compromise or there will be no point in choosing what you offer over what is already available.

The B/E bodies suffer from the wrong upper A-arm mounting, so that would have to go IMO. A bodies are good there.

Along with the arm mountings being wrong, how about the 60's/70's factory tolerances? This may be a way to get that corrected too.

Just an observation from an Engineer with an MBA that likes to go fast as much as the next guy...


You are essentially doing what XV did to some extent, from what I can see. The history that I know was they went belly-up and were bought-out from a previous employer. They aren't necessarily today's hottest suspension manufacturer with product flying off of the shelves....again, from what I can see at this vantage. Maybe they are and I am just not aware.

With that in mind:

The number of people racing Mopars is very low.
The number of people racing Mopars at a highly-competitive level to necessitate drastic suspension changes is far lower.
The number of people getting into racing Muscle Cars is not necessarily booming either.

The target market here is minuscule, unfortunately. Basic business practices will tell you with that low of volumes, the cost will be high, margins will be low and it may not be as successful as you suspect. XV offers, to some extent, what you are talking about doing...and honestly...I can't remember the last time I have seen someone comment about owning an XV suspension system.

You may be trying to solve a problem that there is no sustainable market for.

The key here is bang-for-buck, walking the supply/demand curve to increase volumes. There has to be a target cost and level of variation you can withstand, you can easily hit a pricing threshold that will scare away the majority of those even looking at major suspension changes for these cars.

An XV front system with front brakes is around $7,750 and I haven't even gotten it to my front door yet. Sure, it's probably as good as it gets today, but that is a significant amount for the small market that exists. I can buy what Hotchkis has today for the front for about $1,600, rebuild the steering box for $400 and put $1000 in front brakes [~$3,000]. I can take that box of parts, install it over a weekend and go be pretty-darn competitive. Somewhere along the line someone has to be convinced to spend 158% more to go to XV.

What can you do to convince that small market your product is worth "X" amount more?
What will you have to convince that small market you are better than Option A or B, your direct competition?




I know my post wasn't warranted, but I wanted to throw it out there...

If you're looking for some inspiration, the 73+ B bodies had the upper control arm and shock mounts as part of the k-frame. With that system, relocation would be easier IMO.

You have many great points Goody I agree as well.

I have done this and my `Cuda only handles as good as my beater Corolla. I drive my muscle car not because its faster around a corner but rather its more fun and satisfying driving a slow car fast. For precision handling I drive my S2000.

Another reason I stuck to stock type suspension besides cost is because of the durability. I would like to see a Mopar with an aftermarket tubular K frame setup survive all the jumps the black 68 Charger does in the movie Bullit and only then will I be impressed.

You are 100% correct. I am building a setup for just one customer, so unfortunately, he absorbs the design and fab cost. He is fine with that. I am just trying to determine if I want to build a production jig or a simple one off jig to build his parts. If I do the production jig and had a few people that wanted one, I'd cut my customer a little slack on price and spread it out evenly. This is Mopar stuff. I know there will never be a large market, and more importantly, not much profit. I'm fine with that. Doing this kind of stuff and working on the older cars really has no bearing on my main business, so call it. "just for the fun of it". I have NO intentions of going into the suspension business, just as I have NO intentions of ever doing another LX conversion. I did it, it was cool, and I'm done. If I make just the one, I'm happy.

The MBA is correct on a few points, except the problem I saw was with XV was over marketing, mainly they promoted their system as being super fine tuned with more post testing then I can count, but when it came down to it, a lot of the system were generic, you can't have "finely tuned suspension" that fits every car, and costs a small fortune, and then get defensive with your market when they want some technical answers.

I believe there is a market for high end niche clientele. The MBA will kick in when the development costs are absorbed in the initial prototype, and the solution then can be offered to an increasingly wider market as production slowly ramps up and costs decrease. Keeping it pricey does make it more desirable in many cases. It costs more, it must be better, can't wait till my tax refund check shows up mentality.

The best feature hopefully, is better performance. The downside, it can't be a universal solution to fit everyone's combination, and if does, it will be a big compromise, and just join all the other garage produced RMS iterations over the past decade.

What I am feeling here, this will be the real deal, by someone that is willing to follow thru. And the more its attempted to be copied by others, all the more proof it is the real deal.

I would like to see the ability to use the z06 calipers and rotors, so custom spindles that would accept the Brembo Calipers and carbon fiber rotors...saves a lot of weight and mega stopping ability. Tim

I know the XV uses some "corvette" type parts, but I'm not sure of the extent. How about designing something that could utilize the C5/C6 UCA & LCA along with the spindle and brakes. This opens the door to unlimited aftermarket brakes and rotors. It also allows standard auto parts store replacement parts if needed.