The "Mustang II" IFS Real Info & Debate Thread

Discussion in 'Classic Mustang Specific Tech' started by reenmachine, Sep 17, 2007.

  1. I run hoodless all the time. Next time I am rolling around town, I will see what I can do about mimicking the masking tape setup for what most of us have (export brace/ MC bar). But it may be difficult with the high rise manifold :)
  2. This is a bit misleading. The crossmember, upper A-arms, R&P steering, spindle geometry, basic design, etc all come from the Mustang II. I'm quite sure Heidt's didn't design this; it was the engineers at Ford in the 70's. They don't just carry the name because of the heritage. If all they wanted was a double A-arm suspension they could have stold that from the Camaro.

    As for the eliminated strut rod, I'll contend that is the single biggest design flaw in the *aftermarket* Mustang II suspension. Every time I hear of a FatMan, Heidt's, etc MII suspension failure it has to do with the lower A-arm collapsing in the back. Ford didn't design nor implement it this way - they used strut rods that tied the lower control arms to the frame rail directly in front of the tranny crossmember. I've never heard of an actual production Mustang II having a suspension failure and I'm sure there are some out there with a lot more miles on them then many of the aftermarket MII suspension systems.

    If you haven't guessed by now, I own a Mustang II as well as several 68 Mustangs. They ride totally different. It is hard to compare them really. I personally wouldn't install an aftermarket Mustang II suspension in any vehicle I own. It is hard to trust the engineering behind aftermarket parts labeled with the customary "Off road use only" warning much less an entire suspension system. But that's just me and my opinion; to each his own. Maybe I'm just getting too old and cranky for this new fangled age of restoration??

  3. I don't think it's misleading at all. The crossmember doesn't come from the MII. The presence of a crossmember does, but the crossmember itself is totally different. Same story for the upper A-arms and R&P. You missed the whole point of what I was saying, which was that the general configuration and geometry are the same but the actual components are completely different. Heidt's even repeatedly acknowledges the Ford engineering in their catalog.

    How many of these failures have you heard of with the modern kits? I'm not doubting your experience, it's just that I can't find any photos, direct evidence, or first-hand accounts (just hearsay) of these failures. The only stuff I could dig up had to do with the lower A-arm bolts failing on Fatman MII suspensions, not because of a design flaw but because he supposedly supplied undersized Grade 5 bolts with the kit.:notnice:

    This is one of the reasons I like the RRS parts. You can't get away with the "Off Road Use Only" thing in Australia -- everything they make has to go through rigorous testing and government approval just like the OEM stuff does.
  4. I curious about the recency of the failures too. Catastrophic suspension failure is not an option on a street driven car and if the modern kits are failing I want to know about it.

    The early hot rod MII kits used the strut arm but had conversion kits to mount a true lower A arm. The crossmember was apparently not modified to take the extra load. Every failure I've read about was due to early designs where the crossmember wasn't fully boxed. This caused a stress riser which allowed the crossmember to fail under load from the lower control arm. Every modern kit I've seen has a fully boxed crossmember and some have extra gussets at the rear mount for the lower arm. I have not read about one failure with one of these kits.
  5. To clarify, this is what is misleading in your original post. As you stated just now they still carry the name because they piggybacked on Ford's engineering. IMO, the only thing that is significantly different is the lower A-arm. It's not that Heidt's aftermarket suspension is so much better because they beefed up the crossmember - they had to when they eliminated the strut rod.

    Well I think this illustrates my point. How much testing did Fatman put into their design? I bet Ford put a lot more testing than he did - and they determined you had to have a strut arm. I'm not an expert but when I'm running my car around the track I don't want to end up sucking food out of a tube because somebody used me as a crash dummy for their aftermarket suspension system.

  6. And your point is well taken. I guess as an experienced engineer and suspension geek I trust my ability to spot deficiencies before I put my own or a customer's safety on the line, and run some calculations if I have doubts. Obviously few are in the same boat.

    So, see my comment above RE: RRS.
  7. RRS can't get away with the "for off road use only" warnings because of the motor vehicle laws in Australia but neither can the average guy working out of his garage at home they are very strict on what can and can't be done to a car there, you can't use heim hoints at all on suspension parts there.

    Austraila also doen't have near the problem with lawsuits as we have here in the US, it seems that the US is lawsuit happy and that is THE reason why many parts here in the US are labeled "for off road use only" in fact most aftermaket suspension companies are LLC's or Limited Liability Corporations because the insurance required for producing aftermarket components are VERY HIGH.

    For instance most of Opentrackers parts are labeled that way and i would have absolutely no problems running any of them on the street, i already have the roller perches and love them.
  8. Absolutely. Just because something says "For Off Road Use Only" doesn't mean it's no good, it just means that the manufacturer didn't spend millions for D.O.T. approval and/or can't afford huge liability insurance premiums.

    The flip side is that anyone can make suspension parts, label them this way, and then simply dissolve their LLC or corporation to avoid the liability when you end up on the aforementioned feeding tube.

    I've certainly seen some absolute junk out there from large companies with full-page ads in the mags that I wouldn't put under an enemy's car.
  9. If you have an aversion to aftermarket suspensions, take a look at the aftermarket Fox stuff from Griggs and Steeda. They go head to head in NASA American Iron and AIX. They sell a lot of parts to people who will never race because their stuff is proven to be designed well and reliable.

    There are very few early cars out there on the NASA circuit. The rules won't allow the shock towers to be removed so you won't see a Heidt's or R&C kit on the track, but you also won't see any MIIs. It would be interesting to find out what is being run on the early cars.

    A subjective ride through the countryside is all you need if you don't intend to ever seriously thrash your car. If it feels good to you it is good. If you want to debate the merits of one suspension vs. another then you have to have some objective means of measurement.

    So I ask again: will anyone with a MII suspension go to a track and gather some data for comparison? I might try to go to the Shelby Mid America meet in Oklahoma next year if that would put me in range of someone with a MII suspension to run with. My designs are not for sale (yet) and I won't sell them until I've thoroughly track tested them... unless of course I can get a volunteer crash test dummy! I'll provide a lifetime supply of Gerber's if anything goes wrong:rlaugh:
  10. Doing so wouldn't yield any scientifically valid information unless the cars were identical in every other way and the same highly-skilled driver did all of the driving. There are just too many variables in play for it to mean anything otherwise.

    You know, this kind of scares me unless you can put my mind at ease. What qualifications do you have to be designing and building suspension systems? There's a hell of a lot more to ensuring something's safe and reliable than going out and running some laps. Do you understand how to calculate and design for all of the static and dynamic loads? Fatigue? Oscillating bearing loads? Material compatibilities? Thermal considerations? The list goes on and on.

    I'm not saying you don't, I'm just asking. If you reply saying you're a Mechanical Engineer with x years' experience in machinery design and have done such-and-such in the past I'll be the first to show interest in what you've got up your sleeve.
  11. Yeah, but it seems the general concensus is that they carry no load. Seems a pretty easy experiment to me.
  12. As far as pedigree goes I have a bachelors degree in Physics, not machinery design. I also have 18 years experience as a design engineer in multiple fields. I am now a manager, the head of the Engineering department, including fatigue, stress, structures, dynamics, hydraulics, wiring/electrical, Electromagnetic Environmental Effects (E3), Avionics and Vehicle Managment Systems. As far as suspension design goes, yes, I am self taught. However, I don't feel compelled to "put your mind at ease"... you do what you do and I'll do what I do: design stuff.

    My fabrication skills are limited, and generally I pay for the expertise to have my parts fabricated by reputable qualified shops that specialize in whatever widget I'm working on (e.g. the control arms were made by a company that makes control arms for race cars, etc.).

    A few years ago when Global West and TCP were just about the only choices around, I took a look at their stuff and decided for the price, I would rather design it myself. The only other R&P available was Randall's. He's a really nice guy, but again, I didn't like the way he designed parts of it, so I continued with my own. The TCP stuff also weighs a ton, providing absolutely no benefit. I've derived immense satisfaction by designing everything myself, and my goal has always been to eventually enter the market with a much more reasonable price than the competition by utilizing off the shelf parts and simpler designs. For the moment though I will be content to run with the big dogs on the track (in a similarly prepared street car). I'm not planning to quit my day job anytime soon.
  13. I agree that you certainly don't need to prove anything to me, but that does it anyway. I apologize for my tone, but your post made it seem like you planned "A subjective ride through the countryside" for your test program. It now sounds like you know what you're doing, and, most importantly, you know what you don't know and subcontract accordingly.

  14. This was beginning to sound like the typical "my degree is bigger than your degree" engineer pissing contest I see at work all the time........:rlaugh:
  15. No harm no foul.

    I didn't intend a drive through the country to be a comparison test. On the contrary, for those who simply want an improvement in the stock suspension, there are many ways to skin a cat, and I suspect most of the options out there will provide a substantial improvement. If the owner is happy with it, there is no need to compare it with anything else.

    Agreed that a track test will be somewhat subjective as we can't possibly control for all of the variables, but I'm not trying to declare a "winner", I just want to get a reasonable comparison of a similar car. I'll make note of the differences and take that into consideration in determining what if anything I might change in my designs. One of my ground rules was that there would be absolutely no modifications to the unibody structure. None. Not even drilling holes for the Shelby drop. I don't want to cut on my 40 year old original Mach 1, and I know many others who won't cut on their Boss 302s, but would still like to make upgrades for the track.

    I see the MII as a good basic design that is readily available at a reasonable cost, but it requires (IMO) major surgery. What I don't know is how well it can be made to perform on the track. I think it's unfortunate there isn't some racing class where it could compete with other designs.
  16. Question about shock tower opening



    When I cut out my shock towers I followed their curve as closely as I could. While I don't think the lowest part interferes with the upper control arm; do you think I should increase the opening (at the bottom at the frame)so that it is as wide as the control arm? Pete (Reenmachine) seems to have his more open, judging from his pictures on his website.
  17. If you're just talking about that little bit of lip on the frame rail, it doesn't really make a difference. As you surely saw when you cut the shock tower out, when you cut this lip away the frame rail opens up along that edge. As long as you weld it back closed you're fine.
  18. I cut mine so that when the repair panel is in place the upper arm can still be easily removed. This also goes for the repair panel. Don't bring it so low the you can't remove/replace the upper arm.
  19. interesting, In order to remove the arm once the panel is in place, I'd have to remove the part that holds the top of the shock. I hadn't thought of that. I'll be able to adjust it without problem. Why would I need to remove the arm?

    Thanks for the feedback.
  20. Murphy's law. As soon as you make it impossible to remove, you'll have to. My father taught me to build things as though I may have to take them apart at some point. It may become necessary to replace the arm in the future. In my case I took the arms off to paint the car and had to cut the patch panels to do it.