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pcmenten 01-04-2003 02:06 PM

Front-end design: What does a strut rod do?

Hi, all. :-wink

There's been a spate of posts about Mustang II front-end failures. Some of the better informed posters pointed out that many M-II F/E swaps leave the strut-rod off and that is the root cause of some of the failures. It was pointed out that the strut-rod takes the rotational load when the brakes are applied (a shear load).

Prior to reading that, I had assumed that the strut-rod simply braced the A-arms to stiffen them fore and aft (a tension/compression load). The need to provide for anti-rotational/braking forces never even crossed my mind.

So the question is: What are all the things that a strut rod does?

I have a Gibbon's/Cordoba kit for my front-end and before I go ahead and install it I want to make sure that it will work as intended. It has mounts for the strut-rods, has a monsterous stout engine crossmember, and another crossmember for mounting the ends of the torsion bars behind the cab.

All replies are welcomed.

fatfenders 01-04-2003 03:14 PM

Front-end design: What does a strut rod do?
[updated:LAST EDITED ON 04-Jan-03 AT 04:20 PM (EST)]Paul

First the usual disclaimer. This is important safety stuff. Don't confuse my babble with engineering principles.

The issue you are very often dealing with in the simplest of terms is triangulation. If you add or subtract a component that affects this, (such as a torque rod), the strength of the whole assembly will change. It may change drastically, unless you make a very substantial change in the material used (sheetmetal thickness, rod diameter etc), or restore the triangulation with gussets. Some manufacturers of street rod gear have removed Fords engineering in the name of beauty without appropriate testing. It's a simple fact. They don't have the sales volume to finance proper testing.

Now back to your Gibbons IFS and referring to Joe's PICs from his gallery. The max stress on a RWD IFS is during braking. The issue appears to be a non-factor on your kit. In my opinion, the torque rod totally resolves the issue.

Now as you are fully aware, the Volare does not possess a torque rod. It does however have a huge torsion bar that mounts at the lower control arm on an angle. I think this alleviates the fore-aft issue. Whose system is stronger? Probably yours, but I believe we both will survive our IFS installs.

I don't think Niolon's IFS is unsafe either as long as he adds gussets and watches for cracks. I do think a non-beefed low end MII kit with a big block in an F100 is a potential hazard. Sorry John, I would rather offend you than help kill you You better gusset that puppy until you run out of places to put any more. We kind of like you here on the forum.

I don't think the stress of up and down movement is a problem. Unless of course you design your IFS in such a manner that bottoming of suspense occurs. All guarantees are null and void when you do this. A lot of ultra slammed rodders are asking for it on this issue.

Hope this was on some worth.

286merc 01-04-2003 04:09 PM

Front-end design: What does a strut rod do?
DeWayne, Im amazed.

You actually make sense when you make the effort:-fire

I'll add to it by stating that no truck or heavy car should use the economy kits. Use the HD ones that retain the strut rod or consider the Dodge Dakota setup.
Ive no opinion on the other Mopar swaps, havent seen any up close.

I'd rather take flak also instead of sending flowers.

BlueOvalRage 01-04-2003 05:09 PM

Front-end design: What does a strut rod do?

I can speak from experience that you should have no problems with installation or strength whatsoever. The Cordoba front end parts are similar in girth to some of the light trucks with IFS that I've crawled around under and the torsion bars are only a shade lighter than those on my '97 F-150. Incidently, the torsion bar IFS in my F-150 bears a remarkably striking resemblance to the Cordoba system albiet modified to accomodate the 4 wheel drive. That says a lot about the design since it first showed up under a Mopar in the early 60's. My buddies later model Chevy 1 ton 4x4 has got the same sytem. As long as you don't get cute and try to eliminate the strut rods, you will be fine. My installation has been very straightforward thus far. The only snag I had was with the strut rod mounts and I'm not so sure that I just didn't have a shorter set of rods than the kit was intended for. Everything else just fell together. After close examination and a little cyphering, I concluded that it was unnecessary to weld the crossmember to the frame and just added a couple of extra bolts to each side. IF 4 3/8" and 1 1/2" bolts on each side won't keep it under there, I don't know what will. My goal was to prove that it is possible to have hassle-free bolt on IFS and also be able to mock the entire chassis and powertrain up for fab work and fit and then be able to completely dissassemble the frame for an Earl-esque blasting and paint job with out having to weld/unweld/reweld the crossmember. I like Niolon's truck, but not that much!:-X05

jniolon 01-04-2003 05:54 PM

Front-end design: What does a strut rod do?
Fenders, Paul, Rage, et al...

I appreciate your concern for my longevity and I share your concern.. this is the very reason my MII install has slowed to a snails pace. We (Dave and I) are researching the failures and studying, asking questions, calculating what would be the proper avenue of attack to prevent this from happening to my truck..

The reason for failures shown on the HAMB and RoddersRoundtable boards (and others) has never been proven to be any one reason since analysis was never done... but contributing factors were mentioned as being, poor installation, poor maintenance, abuse of components (potholes, curbs, neglect) and the removal of strut rods which put extra stress on the components... normal intelligence should remove the poor installation/maintenance/abuse from the equation.. at least in my case...

The last part (removal of strut rods) is being addressed as follows:

Rick Johnson of sent the attached pics of a MII install on a 40 plymouth.. while it isn't a F-100 the crossmember and frame is similar enough for example.. Thanks Rick for the pics and the advice !! Look at the next picture...

the support tube for the lower control (behind the crossmember) should be full welded to the crossmember. An additional tube (installed where the blue box is shown in the crossmember) should also be installed and welded to the crossmember front and rear plates.

You can see Rick's correction for the strut rod as an additional brace added to the control arm mount and welded to the frame... This should help transfer the braking forces of the lower control arm to the frame. As well as the twisting force on the arms in turns ...this is addressed in other pics below

looking at the next picture ... the view is from behind and under the crossmember... you can see Rick's added brace much clearer in this picture... he has added a gusset plate from the support tube over to the rear plate of the crossmember... this will take the twisting force of the control arm in turns.. I plan to add an additional gusset from the support tube up to the crossmember (on top of tube) as shown by the yellow triangle... again transferring some stress from the arm to the crossmember...

When all the welding is complete... the ends of the crossmember will be completely boxed which will eliminate stress points that some consider contributing factors in the failures shown on the other boards..

this last picture gives you a top view of the added braces...and some trick engine mounts for the mopar mill...

We think that the additional supports, braces and boxing will significantly strengthen the MII unit and serve to support the BBF and my BB (bigbutt) safely and securely down the road... I'd certainly welcome any comments and suggestions.. I want to do this right and I'm too far into it to back out... 'course that's what I said with a completed Volare clip wasn't it Dewayne...

hope this is of some help to you guys... I have some larger copies of these pics I can email if you need them... this is my first attempt of posting on the board and the quality isn't the best...

be cool... :-X06 and with that said... get off my butt about my MII :-X10


john :-X06 :-X22 :-X04 :-X25

fatfenders 01-04-2003 06:29 PM

Front-end design: What does a strut rod do?

I intend to study your last post hard and I'll be back. For now, one small thing to clarify. Quite a few here are already convinced the whole MII idea is flawed and can't work no matter what. DO NOT count me in that role call please.

I am not yet convinced MII can't work in an F100 because...... the world is full of morons installing things wrong. Sorry but there is no nice way to say it. I have seen too many garbage IFS hackjobs (and other rodding tricks not related to IFS) performed by people with no regard for human life. Their own and sadly the lives of innocent bystanders. It angered me when I saw this working in a real shop (where everything wasn't painted camouflage green or desert sand)

Anyway, while I am not so sure MII is unsafe for F100, I am sure John is going to push it too it's absolute limit. Put it in an F100, install a 460 with heavy auto transmission, likely lower it past it's geometry designed and thoroughly tested by Henry. Let's not forget we are going to lose the torque rods too. What else should we do to complicate this. How about plating everything so we can add some hydrogen embrittlement issues (did I say that right engineer guys?) I think you can make your ride safe John but it won't be easy and we'll notreally be sure until you drive it a long time and monitor it. I know we are being hard on you John, I expect the same when Volares start breaking.

Last thing and then I am heading to the garage. The purpose of this thread is to make our trucks safer. PLEASE DON'T TURN THIS INTO ANOTHER "HA,HA YOUR GONNA KILL YOUR FAMILY WITH THAT MII" crap I read on other threads. John, and Paul and others have already laid down the money. They have to try to figure out how to make it work safely now. Cut the IFS out and put it in the dumpster isn't going to happen so don't go there please. Stockers with engineering talent ought to help out too if they can. Niolon and others have sure been there for you.


jniolon 01-04-2003 07:58 PM

Front-end design: What does a strut rod do?

I agree with most all you say... but... (there's always a but !) here's my take on the whole MII failure cloud.

I'm not totally conviced YET that the MII isn't a good application for a F-100 even with a big block... I've seen two in a heavy sedan, driven questionably by a STBXW (soon to be x-wife) That in itself adds several dimensions and a couple of time zones to the failure equation... I'm not trashing her driving...just saying that attitude could also be a contributing factor. The others include possibly... weather, salted roads, road conditions, installation expertise and periodic maintenance/inspection... too many factors and too many miles for me to make an educated guess on cause. I'd disappointed that Gary Heidt didn't do the analysis that would have set a lot of minds and customers wallets at ease.

The other failure was in a truck and there was very little detail and discussion on that one... so I'm reserving judgement there also.. Not that I don't believe the failures, but I can't put a finger on a cause and that troubles me... I like to know reasons why something works or why it doesn't.

But... (here's another but !) I don't know the total number of crossmembers that Heidt's, Fatmans, TCI, and Juniors Crossmember and Pet Store have sold and installed over the years... must be tens of thousands, right ??? If there were a large percentage of failures (like Pinto gas tank explosions) I think we in the rodding arena would have heard about them by now ??? don't you think ?? If you say that 20,000 were sold and 10% (i think that's very high..but anyway) were put in F-100s... that's 2000 units installed with whatever expertise available. Now consider that we only heard about two.. and say the failure factor was 10 times that... 20... that also seems high but anyway... that is still a 1% failure rate... I don't know if the big three do any better than that ( what was the percentage. of Pinto tanks that blew ??)

All this rambling is simply trying to say that I'm going with the MII... gonna do all I can to beef it up and enjoy it. Granted I will drive it... not as hard as Fenders thinks but it will be driven... but given what I know now... frequent suspension inspections will be done... but I think I'd do that, even without the reported failures...

I agree that our goal here is to have fun... and have it safely... 'least that's what I want to do.. But I've got enough faith in me and especially in my drag car building guru Dave that we can do this thing properly and safely and have a good time after...

As for the ya-ya and ribbing... hey I love it !!! besides all you guys are just trying to compensate for your small.... displacements
:-X04 .

If you're cool enough :-X06 ribbing and kidding are part of your lifestyle... and one of the best parts of this board... I take everything good naturedly and in a brotherly spirit... and for those who want to be nasty and unfriendly... well I don't even like them enough to get mad at them...:-X10

cool on buddies :-X22


Franklin2 01-04-2003 08:02 PM

Front-end design: What does a strut rod do?
Awhile back I read somewhere about the upper a-arm mounts not being correctly utilized in the MII kits on the market. I seem to remember a engineering guy commenting on how the original upper arm studs where mounted by the factory, in the same plane as the a-arm , not at 90 degrees like the aftermarket kits. In other words, the original design did not have the slotted holes with the a-arm studs sticking through the top. The factory mounted the studs pointing toward the engine, using shims behind them for alignment. He talked about how this put the studs in a shear load instead of a compression load, and they weren't sized correctly for that.
I haven't kept up with this subject lately, and don't know if it's true or not, but wondered in your research, have you guys come across this little debate?

jniolon 01-04-2003 08:30 PM

Front-end design: What does a strut rod do?
first time I've ever heard that ??????

think you can find where you read it for some more research ???



fatfenders 01-04-2003 08:35 PM

Front-end design: What does a strut rod do?
[updated:LAST EDITED ON 04-Jan-03 AT 09:37&nbsp;PM (EST)]<<<Fenders,
I agree with most all you say... but... (there's always a but !) here's my take on the whole MII failure cloud.>>>


What do you take issue with? I believe you asking a lot from an MII. I have no idea how you drive. I just know you are gearing up for a heavy install and a powerful drivetrain (I am giving you the benifit of the doubt that you know how to make a BB run. Just holler if that's not the case and we'll square you away. :-X10


PS You straight axle boys must be thinking, "We don't need no triangulation, just don't skimp on the iron in the first place. :-X10

286merc 01-04-2003 08:55 PM

Front-end design: What does a strut rod do?
I hope that ALL of you will remember that Ive not come out and denounced the entire M11 principle. In fact my first post here on the subject was about the STBX and was completely non commital. BTW, a 46 Ford coupe is not exactly a heavy sedan.

Ive personally decided to not use one in the 46 p/u because of concerns of mfg cover-ups and the fact that suspension engineering is something Ive no real expertise. My view may change by the time I get to that project.

Since this forum has limited membership Id suggest that those pictures and explanation be posted on HAMB and RRT where several people with credentials reside.
If it was my vehicle Id be looking everywhere for comments and just remember to toss out the obvious ones from the clueless.

Another friend here in town has a 460 in his 56. He has no computer to follow discussions with. Was a GM mechanic for over 40 years.
He builds Fords as a hobby and now as a retirement sideline.
He had several try and convince him to use the Heidts but refused. Told me that thing would break under braking a year before STBX. Here is a guy that lives in the same 10K population town. Coincidence or a more general feeling among those that understand this stuff and are not swayed by full page ads and travelling circuses??

BlueOvalRage 01-04-2003 10:16 PM

Front-end design: What does a strut rod do?
Franklin and John,

I read your comments on the upper control arm mounting arrangement with great interest. My Gibbon kit does just the opposite. The Cordoba had the slotted holes and the bolts fit in vertically from the factory. Gibbon rotated the cross bars 90 degrees in it's crossmember kit and mounted them so the bolts fit in horizontally and uses shims to set the camber. It had never occured to me that this might even be a stronger method of mounting it.

PlumCrazy55 01-04-2003 10:38 PM

Front-end design: What does a strut rod do?

>hope this is of some help to you guys... I have some larger
>copies of these pics I can email if you need them... this
>is my first attempt of posting on the board and the quality
>isn't the best...

I appreciate your research in this matter and your excellent pics.
I will be adding xtra bracing to the rearward facing tube for the lower control arm on my Superide II.I'm a little farther along on my project(the 460 is in place,the exhaust is made,the frame is painted)but I think it is a very important mod that needs to be made.
Thanks again!

fatfenders 01-04-2003 10:53 PM

Front-end design: What does a strut rod do?

Email me the PICs if you would. I am getting old and blind. Not too many at once please, I don't have DSL.


While I do think you have made up your mind on this subject, you have the right to as you have definitely read plenty of opinions on the subject in your internet travels. There is definitely some evidence to support the opinion. If you have, you aren't alone. Whether you have or not, its time to take a look at John's PICs and suggest improvements if you can. A number of the IFS threads have ended with guys getting mad. There's no value in that. There are forum members who are welders, engineers etc that can offer insight if they don't get chastied for it. There really isn't a huge problem with that here. I can't believe the way the "experts" on HAMB treat people. I won't be back there after I saw the way a fellow 48-60 poster was treated after asking an innocent question.

Or even back to the original post. The "Bat Clip" looks strong to me. Nonetheless, there aren't 10,000 of them on the road and they haven't had any serious R&D on a F100 either. If someone has an issue with it and raises it in a civil manner, Joe and Paul would be fools not to look at it with an open mind, and make appropriate adjustments.

Even my time tested Volare takes some hits on the No Limit Video. I had the MIG fired up before the VCR tape was done. I believe my truck weighs several hundred pounds more than a Volare wagon. I would be a fool not to take every precaution.

We aren't likely to prove or disprove a particular IFS is absolutely good or bad to the owners satisfaction. We can offer suggestions to make the best of all of them.

I am rambling so I better end this.


pcmenten 01-05-2003 12:08 AM

Front-end design: What does a strut rod do?
Dewayne, Carl, John, Joe, Franklin, et al;

Great discussions. I learn so much by reading and considering everybody's ideas. I really don't want to trash the MII IFS. I have no doubt that it can be made to work. But I do want to learn any lessons from the experiences of MII owners. One of the lessons is that I need to know how a front-end is supposed to work before I start installing one so that I can accomodate the engineering requirements.

Dewayne, dispite your protestations to the contrary, you often supply me with useful, even critical, engineering information. Many thanks.

John, I am sure that many, many MII IFS's are on the road. But I think a lot of the MII IFS's are installed on garage queens and show cars. What I liked about the information about the MII on the STBXW's car is that it was a daily driver. I suspect that there was a specific circumstance that helped produce the failure in that application. Not a maintenance or installation issue, but something like a steep driveway, or railroad tracks on the way to work, or heavy stop-and-go use, all of this exacerbated by big wheels and tires, and a big engine.

My hope is that we learn enough about what the requirements are so that we can design modification that target the specific needs of the application.

Several people brought up some excellent points. Franklin mentioned the mounting geometry - shear vs. tension/compression. I think this needs to be understood and addressed soon. Joe is in the process of installing his Gibbons/Cordoba IFS and I am concerned that he get it right. Lets talk.

Back to the original question; function of strut-rods. Some things that Dewayne, Carl and John said go me thinking. First some review to put this in context. The strut-rods on a Cordoba angle in toward the center of the car. It occurred to me that the front end of the strut rod must be very close to the axis that the A-arm rotates around. This would help keep the arc of its travel in the same arc as the arc of the travel of the A-arm.

Whoops. This is getting long. I'd better post this and continue in another post.

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