To much mathy for me :nerd: But I like mine they helped me dial in caster.I think the ride is better also. I've pounded them pretty good since putting them on with no ill effects.
You have a PM. BTW.

 

I think you're assuming the strut rod moves up and down and looking at the side view of the car, the ball joint end will move in an arc like <) The strut rod actually rotates around the axis made by the front strut rod mount and the lower control arm bushing. From the side view the balljoint end will move straight up and down perpendicular to the axis. As long as the front pivot point is on the axis, there will be no change in the position of the ball joint

The strut rod and lower control arm is no different than an "a" arm. Think of a door on a house. Compare it to the upper control arm. Door knob is the ball joint and the top and bottom hinge are the bushings. The lower arm will look similar to the center and upper hinge on the door with no bottom hinge. No matter where on the door you put the hinge, as long as it's on the jamb, the door knob will move in the same arc.

 

Moving the strut rod pickup point will change geometry slightly, but is it good or bad? Did Ford have it right from the factory? With the poor camber curve I don't assume anything was optimal.

 

Sorry Rooeng but I respectfully disagree. On a lower a-arm the pivot points are on the same axis so the end of the arm moves straight up and down. The mustang design strut rod is not on the same axis as the lower control arm pivot point causing the end of the control arm to move in an arc. This is why you need a rubber inner bushing or monobearing rather than a roller bearing. Your door hinge analogy would be more like a hinge on the jamb and one on the floor.

Rick

 

Can you explain what defines the pivot axis the strut rod and LCA follow?

To the OP, there is software that can calculate movement given dimensioned locations. A demonstration version I used already had 1967 points input and allowed a few alterations before no longer allowing changes. I assume if the software was purchased, the data points are included.

 

I'm not at home so I can't look at my car. My thoughts are this. If the LCA and strut are parallel to the ground, I think the shorter option would be better. Under braking as I imagine it, the tighter radius would pull a little more positive caster under braking for better stability. If the frame mount is higher, I think I would want a longer strut since there would be less change in caster. I think the caster would go negative in this case. With the shorter strut I see it would reduce caster.

To be brutally honest and not directed to you personally but as a general statement. Why do we build parts like this? To show off what we built. Does that mean our engineering and manufacturing up to snuff? What scares me is the threads. I know how to cut threads. You're going to end up with a sharp root in the thread. A good point for a crack to start. Personally I would want rolled threads here. Shaun spends a lot of money and I do mean a lot of money on a PE to inspect his designs. Then he has very, very high quality of manufacturing. He assumes the liability. To me it was a no brainer. I would feel devastated if a suspension part such as this failed that I built and some one ELSE got hurt. And no I am not rich. This was very hard earned money for me but a bargain from a safety point of view.

Bottom line I think there's more to be gained from getting rid of the rubber bushings more then any thing else. It's like trying to decide on what shade of blue you want when only black or white is available.

A testimate of how good adjustable strut are. When I finished my suspension, SoT upper & lower control arms and struts I still had front drum brakes. At 50 MPH I could take my hands of the steering wheel and jamb on the brakes. The car would stop dead straight. No pulling or anything else. It was very stable.

 

I'd go with a spherical bearing at the front placed in a saddle mount with a 1/4" urethane isolator.

Simple, yet effective. Accommodates the swing through the arc and the rotation of the strut rod as it arcs. Located properly a stock rod could be used.

 

I built spherical bushing ones for mine that retain the factory mounting location and factor strut rods. I've been testing them for a couple years now. Here is a pic: 1967-73 Mustang Spherical Strut Rod Bearings ? Vintage Race Works

 

As a retired major O&G engineer (ME) via international engineering/project manager roles I do hope those providing their view can/have run the numbers... This is not arm chair stuff.

 

Yea, I'm thinking I want to be in the 10s of thousands of load. I figure tires can likely deliver a G of force at best divided by two since most of the stopping is on the two front end that's 1500 lbs. Now a nice factor of pothole safety and I'm thinking 15-30 K lbs radial load Heim Joint. I ran Teflon lined heims in my watts link to keep it from clanking, seems to work nicely. Might run em up front, just gotta spend some time on the charts to pick the right ones gonna aim north on the size. Ball joints are a different design and steering doesn't take the loading that suspension does so I'm gonna lean large and radial load on this one. THanks for the ideas.

 

QA1 XM series rod ends are pretty tough.

 

No kidding! 5/8" shaft 30k lbs radial force $23 each not too bad. They are used in 4 links and ladder bars. I think I could be comfortable putting my kids in the car with these. THANKS!!!

Merry Christmas to me:

QA1 XML10-12 X Series Rod End, Chromoly Steel, 2-Piece, Each 721XML1012 $23.99 2 $47.98

Thin Steel Jam Nuts, 3/4-16 RH 1750247 $0.99 2 $1.98

Thin Steel Jam Nut, 3/4-16 LH 1750447 $0.99 2 $1.98

Speedway IMCA Approved 3/4 Thread Swedged Steel Tube, 12 Inches Long 91034234-12 $9.99 2 $19.98

Combo Exhaust Pipe Mandrel Bend/Header Tubing, Mild Steel, 2-1/2 Inch 91013896 $16.991 $16.99

GT Performance 21-1625 Euro Horn Button, Ford Mustang 910211625 22.99 1 $22.99

 

For load rating, I'd start from what we "know". What is the radial load rating of the rod end typically used in the strut rod kits? In the end, I really do believe it's "overthinking it". I don't think you will ever notice the pivot point being moved by an Inch or so. The "best" way is probably the CA method of removing the factory flange and welding in bolt sleeves, but most won't want to cut up their car to do that.

Edit: You may not need to cut out the factory flange, though I would like to see the sleeves welded in and gusseted:
http://forums.vintage-mustang.com/mod-custom-forum/606660-simple-home-made-strut-rods.html

 

I used these Mark if you didn't get the Pm I sent
JEGS Performance Products 64136: Three-Piece Rod End with Jam Nut 5/8" Hole | JEGS
Ball: Heat-treated, Chrome-plated 52100 Steel
Body: Black Oxide Coated 4130 Alloy Chromoly Steel, Cold rolled threads
Race: Self-lubricating PTFE liner
Static Pull: 3/4" size = 21,400 lbs
Includes zinc-plated steel jam nut
Like I said I've pounded mine pretty hard ,,you drive some of the same roads I do.You know how bad they can be.Not to mention the drop off from my garage to driveway
Overthinking DIY strut rod mod,,,Yup

 

So here is where I am now, do this OCHO style - pretty slick:

http://forums.vintage-mustang.com/mod-custom-forum/606660-simple-home-made-strut-rods.html

or do it with a clevis - if so, what has me intrigued by a clevis, likely U bent 1/4" flat stock, I have been thinking about cutting my stock rubber mounts about 1/4" thick and mounting the clevis in rubber perhaps with the illusion that I wouldn't get so much road noise. HMMM...

 

That seems like a hard hole to drill ,,straight at least.I used a clevis and retained the bushings(poly)

 

Exact force I don't know. I do know that if you use urethane bushings on the strut rod a good pothole hit can and will shatter a solid steel strut rod. People have done so and have taken pictures. Just sayin'. Shatter solid steel. Something to keep in mind when saying this or that is "good enough" to handle the forces involved.

 

Lets look at this statement differently:

The rod has a diameter of approximately = .750 inch.
Let’s assume it is made from junk steel that has a Tensile strength = 55,000 psi

So the area of a .750 diameter equals = .440 in²

If you take the area multiplied by the Tensile Strength you get the force on the bar when it breaks in tension:

.440 x 55,000 = 24,200 lbs. (IN TENSION ONLY!)

That’s a lot of force right?

Now let’s look at the Threads. It’s the same formula except you must now figure the area of the threads engaged.

Let’s assume ¾-20 is the thread size with .500 in of engagement.
Thread area = .156 in²

.156 x 55,000 = 8,580 lbs. (IN TENSION ONLY!)

So as you can see the threads will fail first before the bar will snap. This is in tension only.

Now let’s assume you increase the thread engagement so the rod fails first.
This means we are back to square one 24,200 lbs. in tension is the maximum the rod will see before it breaks.

With all that said, I go back to the statement “broke cleanly”. One has to wonder how changing bushings can break a rod “cleanly”. Let’s take a closer look.

If the rod worked happily with standard bushing and then broke when new bushings are installed. Something doesn’t sound right does it? Forces are the same right? Pot holes are the same right? So what changed? Only thing that changed was bushings. So how can bushing change the laws of physics and modify the steels tensile strength in the formulas above?

The answer is it can’t. The rod with new bushings broke from FATIGUE! Ever take a piece of steel and BEND it back and forth? After doing this ten times what happens to the steel? It breaks - That is Fatigue. Another sign this was fatigue is the “broke cleanly” statement. When steel breaks in tension, it will neck down first then break creating a reduction of area.

To sum it all up, the rod broke from Fatigue and bending moment because the new bushings didn’t allow the rod to articulate or move with the suspension. It didn’t break because of a pot hole.

THE DATA ABOVE IS FOR REFFERENCE ONLY AND SHOULD NOT BE USED BECAUSE OF THE ASSUMTIONS RELATED TO MATERIAL QUALITY AND MATERIAL SPECIFICATIONS.

If the above poly bushing concerns are in reference to my statement :shrug: Keep in mind I also have a Heim joint/rod end in the strut rod now (many miles on poly alone) I've also seen original strut rods bend(alot) before breaking.

 

Lets look at this statement differently:

The rod has a diameter of approximately = .750 inch.
Let’s assume it is made from junk steel that has a Tensile strength = 55,000 psi

So the area of a .750 diameter equals = .440 in²

If you take the area multiplied by the Tensile Strength you get the force on the bar when it breaks in tension:

.440 x 55,000 = 24,200 lbs. (IN TENSION ONLY!)

That’s a lot of force right?

Now let’s look at the Threads. It’s the same formula except you must now figure the area of the threads engaged.

Let’s assume ¾-20 is the thread size with .500 in of engagement.
Thread area = .156 in²

.156 x 55,000 = 8,580 lbs. (IN TENSION ONLY!)

So as you can see the threads will fail first before the bar will snap. This is in tension only.

Now let’s assume you increase the thread engagement so the rod fails first.
This means we are back to square one 24,200 lbs. in tension is the maximum the rod will see before it breaks.

With all that said, I go back to the statement “broke cleanly”. One has to wonder how changing bushings can break a rod “cleanly”. Let’s take a closer look.

If the rod worked happily with standard bushing and then broke when new bushings are installed. Something doesn’t sound right does it? Forces are the same right? Pot holes are the same right? So what changed? Only thing that changed was bushings. So how can bushing change the laws of physics and modify the steels tensile strength in the formulas above?

The answer is it can’t. The rod with new bushings broke from FATIGUE! Ever take a piece of steel and BEND it back and forth? After doing this ten times what happens to the steel? It breaks - That is Fatigue. Another sign this was fatigue is the “broke cleanly” statement. When steel breaks in tension, it will neck down first then break creating a reduction of area.

To sum it all up, the rod broke from Fatigue and bending moment because the new bushings didn’t allow the rod to articulate or move with the suspension. It didn’t break because of a pot hole.

THE DATA ABOVE IS FOR REFFERENCE ONLY AND SHOULD NOT BE USED BECAUSE OF THE ASSUMTIONS RELATED TO MATERIAL QUALITY AND MATERIAL SPECIFICATIONS.

 

THE DATA ABOVE IS FOR REFERENCE ONLY AND SHOULD NOT BE USED BECAUSE OF THE ASSUMPTIONS RELATED TO MATERIAL QUALITY AND MATERIAL SPECIFICATIONS.

I quoted this because it is extremely important that the values given in 67strokers post are NOT presumed to be accurate. (BTW, nice first post)

For those with questions about the math, further explanation can be found here.

Calculating Yield & Tensile Strength - Portland Bolt

 

The reason strut rods break when mounted in polyurethane is because the strut rod must move at it mount with the frame. When mounted in the OE way, the rubber bushings compress as the rod moves up and down. When mounted in urethane, the strut rod can not move and all the stress is transmitted to the area just ahead of the bushing and the rod breaks.

BTW, I've had rods bent on the control arm end a good 15-20* and not break. Why? Because the load was spread over an area of 6-inches or more.

 

Yes, but why does your woodchuck look like he's wearing lipstick?

 

So can I assume I am safe with Shaun's strut rods that I purchased...:laugh:

 

For whatever my opinion may be worth, I would have as much or more confidence in Shaun's strut rod design as in any other option out there. Including stock originals.

 

Some would say our stuff is stronger than trees!

This poor guy hit a tree with such force it ripped the wheel, complete with spindle clean off! They removed our suspension and used it on the next build...

 

Sorry GypsyR – I read the thread fast and through you had said “clean break” – my bad. Most break around the bushing mount from reasons stated in my original post.

No the post was not a copy and paste like you said – I work for the one of the largest bearing manufacturers in the world and this topic caught my eye.

If it was a split longitudinally then it is clearly material defect in the steel. Most likely a roll split from the steel mill, I see it all the time. The new bushings exploited the defect per my original post and stressed it to failure.

Be careful using the spherical bearing in a longitudinal (axial loading) application. The outside race must be properly supported to get advertised maximum load.

 

Shaun - nice strut rod setup. All parts are used in a way they were designed for.

 

My parts showed up today and SWMBO intercepted them and sent them to the wrapping department downstairs. Sigh - so I built a "wrench?" today for the BF3/4-16 die and put the car up on jack stands. I couldn't find a big enough piece of metal in my pile so I took the bar off my chain saw that I shouldda thrown away years ago because the guard and brake broke off.

 

Ok everything is fabricated and paint is drying. So here is the scoop, I was looking at two versions, the Ocho style which is what I chose because it would be easier, and it gives the longest strut rod which I have proven is negligible. I thought it would be easier in that there is no clevis to fabricate or purchase, just drill two holes and your in - yea right...

What I learned is that this easier way is way-way-way harder and quite stressful!!! With the Ocho style, you have to fret (really fret) about drilling the hole "just so" that there is no interference at top and bottom of the suspension swing. This means the spring and shock come out and swaybar is disconnected - both ends. Then up and down a million times to choose the spots with a fixture I built from a 1/4" bolt pointed at both ends wrapped with black tape to a 5/8 diameter so the heim will sit properly. Then transfer the mark from the inside to the outside where I drilled from. In terms of spacers, things happened to work out perfect, width 2.75, Heim was .75 wide, 2 1" spacers from tractor supply and a couple of grade 8 bolts, lockwashers and nuts.

Making a clevis and bolting the system to the old mount is way easier (like the systems you can buy), requires no mock-ups at high and low suspension, just fabricate and throw it on. Unfortunately, the threaded rods I got were too long to go that route and I wanted this done so...

Oh yea, do not underestimate the effort it takes to tap 3/4" steel rod. I would seriously consider talking to a machine shop and seeing how much it would cost if I did it again. If you make a fixture like I did, use Mustang Steve's trick on the back (see image) to get the threads started correctly, otherwise they start off at an angle and about 1/2 in later you realize your screwed and your piece is now gonna be 1/2" shorter - "gee Mark, how did you find that out???".

So, the bolts are trimmed to the right length and everything is painted. Should go on later today then decide what's next. I hope you will all agree that this system should be quite robust.

BTW the weight worked out to be almost exactly the same, I thought the new ones would be heavier.

One thing I learned is that the oil plug on the top of the lower part of the oil pan (you can see it in the image) was lose hence the oil everywhere.

Cheerz,

M

 

To be fair, lets call it Cobra Automotive style. Getting the holes in the correct location takes some time, true. I did not thread the old strut rod. I thought that was too difficult to get aligned without machine shop tools. Your installation looks good. The last little trick is to thread the parts together such that it leaves the lower arm in about the right place and leaves enough thread on the heim for adjustment without disassembling it.