std 4 link vs opt 3 link rear suspension

[Ford & Jeep Fan]

I have owned a stock and later modified 88 GT and am wondering just what is the driving impression difference there is between the two rear suspension designs.
I always though the rear suspension on my 88 seemed to work just fine.
I am very surprised at the lack of information in the brochure where it mentions the option as to the benefits of it.

[svassh]

I found this explanation on the other site:

"4 link best for cruising and drag racing. 4 link can bind in certain cornering situations (autocross or racing type). For cruising it is fine. Good for a drag race type car.

3 link is not quite as strong for racing slicks and high hp engine combinations as compared to the 4 link but it does not have the binding issues when cornering. Great for autocross and road racing. The FFR spec racing cars run the 3 link."

I am in the process of converting my 4 link to 3 link as I've found the 4 link to be a little rough on hard cornering and I want to autocross mine this summer.

With the 3 link you lose the upper control arms but keep the lower. You then add an adjustable panhard from driver shock mount to passenger frame and adjustable bar from axle to top of frame. Then you can set the axle location and axle drive angle.

[rich grsc]

Dump both, go IRS. The 4 link is like riding a truck, and can snap steer without warning.

[GoDadGo]

I've been street legal for just over a year and get No Wheel Hop nor any Mustang 4-Link shimmy and am running the 3-Link.
If you want smooth corner carving and the most comfortable ride possible, then go with the I.R.S.
If you like to play the Stoplight Game, then go with the 3-Link.

Graduation:
https://youtu.be/9WEe6-wdNtA

Tire spin is another story!
https://youtu.be/PCngiKoopkA

Good Luck!

Steve

[rich grsc]

My IRS plays stop light as good as any.:cool:

[NAZ]

Don't mistake the Mustang style 4-link with a parallel 4-link used in drag racing, they are two very different suspensions and provide significantly different performance. The real advantage of a triangulated 4-link like used in the Mustang (and some GM cars) is packaging and cost -- performance and tuning are not a consideration with a triangulated 4-link. A well set-up offset 3-link is a great suspension design and has tuning advantages over an IRS. You'll see 3-links used on asphalt, and dirt race cars. They are also popular with offroad vehicles. And then there is IRS, great in some applications -- not so much in others, but I find them very difficult to tune easily.

For a street car that's mostly used to cruise in, any of these three will work well IF it is set-up correctly. One of the common problems I see with the solid rear axle set-ups is folks get wrapped around the axle trying to set a specific ride height based on some dubious recommendation with absolutely no regard to what angle the LCAs are at. I suspect there are a lot of cars with varying degrees of roll steer out there. Same thing happens to 4x4 vehicles people lift and then experience handling issues. You can minimize that ill handling effect by ensuring the LCAs are parallel to the ground and the farther away from the the more roll steer you'll experience.

[Jeff Kleiner]

You ever seen any of those videos where a Mustang driver gets on it hard when leaving the cruise in and winds up going into the crowd when the back end snaps around? Those cars have triangulated 4 links. Get it?

Jeff

[NAZ]

https://www.youtube.com/watch?v=-ywdw16cZ-I

[Peeker]

I bought my kit and it already had the 4 link. I have never had a car like this before so I don’t know how different they feel with the different rear ends to drive, but I’ve got about 1,100 miles on my car and have no issue with the 4 link, but I’m not racing mine. It is just a cruiser. I had the same thoughts about rear ends when I was looking and if I had the choice, I would probably go 3 link just for resale if I ever wanted to sell. Otherwise, I’m fine with the 4 link. IRS is not cheap and if it’s a cruiser, then why?

[Peeker]

Dump both, go IRS. The 4 link is like riding a truck, and can snap steer without warning.

I’ve driven a truck and I’ve driven my 4 link, and my Cobra is not like driving a truck.

[GoDadGo]

Think about the Evolution of the Mustang's Rear Suspension:

1963-1978.....Leaf Springs
1979-2004.....4-Link
2004-2014.....3-Link
2015-2022.....I.R.S.

Now think about the evolution of our beloved Factory-5 Wonder Cars.

NOTE:..I still prefer the 3-Link because of its simplicity and strength.
............An added bonus for me was it made things easy when I shortened my wheelbase.
............Why would I shorten the wheelbase of my roadster, it was to better center the wheels within the rear wheel wells.

Good Luck & I Know You'll Choose The Rear Suspension That Is Best For Your Dream Machine!

[rich grsc]

I’ve driven a truck and I’ve driven my 4 link, and my Cobra is not like driving a truck.
I understand, but you haven't rode in or driven an IRS. I've had all three, I wouldn't consider a 4-link if I was to buy another, maybe a 3-link if the price was right, definitely 'would' pay for the IRS. You said that the IRS is expensive, yes, maybe a $1000 or so, but if you have say $40k in your car, is $41k a deal breaker? The IRS WILL give a better smoother ride, and if you do full day cruises like I do, you'll certainly know it at the end of the day. :)
When you going to meet up with GCC? Would like to see your car.

[Jim1855]

You ever seen any of those videos where a Mustang driver gets on it hard when leaving the cruise in and winds up going into the crowd when the back end snaps around? Those cars have triangulated 4 links. Get it?

Jeff

Not to disagree with Jeff but I've seen all types of cars and suspensions go sideways and backwards when leaving car shows. Most times I think it is lack-of-experience based rather than a suspension type. Certainly, one type of suspension or lack of proper set-up has an effect but is it as much as the driver?

Jim

[Jeff Kleiner]

Not to disagree with Jeff but I've seen all types of cars and suspensions go sideways and backwards when leaving car shows. Most times I think it is lack-of-experience based rather than a suspension type. Certainly, one type of suspension or lack of proper set-up has an effect but is it as much as the driver?

Jim

Of course Jim, but some suspension systems are less forgiving of a ham fisted driver---the triangulated 4 link which controls body roll by intentionally inducing a bind being one of those. ;)

Jeff

[NAZ]

I agree with you Jim, any suspension design can launch squirrely and unpredictably if not set-up correctly, or when there are other factors that result in unequal and inconstant traction. But some designs are just simply inferior to others and will cause you to run out of talent much quicker than a well set-up suspension that hooks and leaves straight. The triangulated 4-link is a system of compromises and has inherent design issues, one big one is lack of adjustment. The next worst design for launching a car hard is the Mustang IRS. Again, compromises in the design and lack of adjustment. I'm not opposed to IRS, I built my latest race car with IRS but it uses radius rods and trailing arms not a-arms, and all can be adjusted to change anti-squat and camber gain to improve traction. It also uses some very sophisticated three-way adjustable internal bypass shocks and is light years ahead of a Mustang IRS.

But the best all around performance suspension you can get from FFR is the 3-link. Even that is no where near as good as it could be but if you have the knowledge and skill, it can be made to work far better than the Mustang 4-link & IRS.

[J R Jones]

Not to disagree with Jeff but I've seen all types of cars and suspensions go sideways and backwards when leaving car shows. Most times I think it is lack-of-experience based rather than a suspension type. Certainly, one type of suspension or lack of proper set-up has an effect but is it as much as the driver?

Jim

Suspensions don't wreck Mustangs, people do.
jim

[NAZ]

Suspensions don't wreck Mustangs, people do.
jim

Wow, can't get more concise than that. That's a great tag line -- I'm gonna have to plagiarize that as it's simply too good not to repeat.

When you run out of talent, bad things happen. Suspensions don't wreck Mustangs, people do.

Jim, I love it!

[J R Jones]

https://www.youtube.com/watch?v=-ywdw16cZ-I

NAZ
This video is cringe worthy, but I had to watch it 2.5 times.

At least two contributing factors demonstrated there:
Building one's personal "suicide machine" (Bruce Springsteen)
and the "karaoke effect" they really can't drive but there was an audience.
jim

[Jim1855]

At London a few years ago a gentleman spun 180 on the charity ride event and went over a curb. My understanding is it was a fairly new car for him, months or maybe weeks old. Suspension, sidepipes some body panels were all damaged, not to mention his personal image. I'm sure he made an impression on his insurance agent, although not a favorable one. He certainly impressed the crowd.
At LCS in years past I've seen truly impressive driving skills, although some perhaps were not the smartest moves. This comes from a guy that ran 104 in the longer version, smart, probably not, fun, oh yeah.
Jim

[PG_Cobra]

The 4 link is a compromise. Use the Ford rubber bushes and get the infamous Fox rear end steering with the axle moving laterally. Install urethane bushes and get the binding issues with snap oversteer. Don't forget the Levy 5 link system that looks good. I added a Maximum Motorsports Panhard bar to my 4 link with Fox bushes on the axle, adjustable UCAs for pinion angle and MM LCAs. So far its working well with total absence of any quirks. My car is purely street use.

[Derald Rice]

One of the BIG problems with the Mustang 4-link in a FF cobra is that the cut down Mustang springs
tend to rotate, and then when they rotate, the ride height changes.

If you go with the 4-link do some research to see what the various methods of securing the springs have been.

Don't know if coil overs on a 4-link has been tried, but it would obviously solve the spring rotation / ride height problem.

[cgundermann]

Ford compensated for the four unequal length control arms with large soft durometer rubber bushings which as mentioned, induced "snap steer". I drove a Highway Patrol special duty 5.0 Fox body Mustang for many years and was involved with many pursuits. That snap steer is scary thing and many a troopers ran a foul to it. Had several driving situations where I thought I was going to have my seat surgically removed from my keester...

Also was a collision reconstructionist and investigated a high number of Fox body Mustang collisions in which oversteer was a causation. My MK4 has a three link and is a much better handling car than a Fox body Mustang. The Daytona I recently ordered will have IRS which I'm excited to drive. Just my old & tarnished two cents...

Chris

[Norm B]

One of the BIG problems with the Mustang 4-link in a FF cobra is that the cut down Mustang springs
tend to rotate, and then when they rotate, the ride height changes.

If you go with the 4-link do some research to see what the various methods of securing the springs have been.

Don't know if coil overs on a 4-link has been tried, but it would obviously solve the spring rotation / ride height problem.

I started out with the cut down Mustang springs with a four link suspension but recently upgraded to coil overs. It had some quirky handling characteristics. Most, I believe, caused by the different spring and shock rates between the front and rear of the car. Hard driving caused the softer rear to flex and load up in a corner. As you came out of the corner the suspension unloaded and the rear of the car would move about 1/2 an inch towards the direction you had been turning. Kept the four link but upgraded to FFR Koni coil overs. The ride is stiffer but, the car tracks much better now.
Note, I am not running the OEM control arms. I have Granatelli tubular control arms with poly bushings except the upper bushings on the differential. Those are the OEM rubber bushings. This was the recommended config to avoid binding.

Norm

[GoDadGo]

Hey FJF,

Here's a thought inspired by Norm B's comment, since you are on a budget and have the rear end, just upgrade the 4-Link control arms.
I've got Spohn lowers on my 3-Link and they work fine since the adjustable control arms allow you to dial in your pinion and thrust angles.

https://www.spohn.net/shop/Factory-Five-Racing-MK3-MK4-Roadster/

I totally get wanting to run what you have because that's why I'm running an All Dart 383 SBC with a ZF 6-Speed.
You can always upgrade to a 3-Link in the future so what the heck, run What-Cha-Brung!

Good Luck, Happy Wrenching & Watch Your Pinkies!

Steve

[Peeker]

I understand, but you haven't rode in or driven an IRS. I've had all three, I wouldn't consider a 4-link if I was to buy another, maybe a 3-link if the price was right, definitely 'would' pay for the IRS. You said that the IRS is expensive, yes, maybe a $1000 or so, but if you have say $40k in your car, is $41k a deal breaker? The IRS WILL give a better smoother ride, and if you do full day cruises like I do, you'll certainly know it at the end of the day. :)
When you going to meet up with GCC? Would like to see your car.


Rich,

If you look back at the original post, the answer you gave here was perfect and that is what he was looking for. In your original response you said dump the 3/4 link and go with the IRS. I don’t believe that helped him make a decision but this response was what he was looking for. As a matter of fact when I was originally looking for a kit, those are the questions that I had and imagine most of us have had.
As for it only being an upgrade of $1,000, I don’t see that. FFR’s price is a $3,199 upgrade. I’m sure you can get a used one for considerably lower, but how much is required to then get it ready to install? (I don’t know the answer to that question. Ask me how to fly a 737, I can give you an answer. Ask me about IRS’s and installation, I’m lost).
The original post never addressed how the car would be used. My car is not for the track. It’s to take my wife, kids, or grandkids out on nice days. If the weather is not nice, my car will not be out. If I were gonna track the car, I would have upgraded, but I’m happy with how it drives, and the only person that has to be happy with my car is me.
As for when you’ll see the car, I just got pics from my painter on Friday. He was doing cut & buff. I anticipate having the body on the chassis in the next week or so. As you know, there are a lot of things that still need to be done once I have it back home but it will be out in the spring. I’m giddy thinking about it.
Ed

[J R Jones]

I have a theory that what may be the issue with the Mustang upper control arms is that with side load and displacement, one arm angles longer and the other angles shorter.
Before I launched into a complete redesign, I would try a panhard bar to limit lateral displacement. A Watts linkage would be better, but more complex. I would use rod ends on the panhard, not soft bushings.
jim

[weendoggy]

OK, since everyone else has .02 worth, so do I. (Ed) if you plan on using as suggested, the straight axle is fine. Although I would NOT use the 4-link and instead opt for the 3-link w/PB. You'll be happier knowing the axle will stay where it should and not go "side-to-side". The ride is definitely different between the IRS and solid, but I do see your point on cost. Mine is IRS but have driven a lot of solid axle cars. The 3-link is a must and most who built there's years ago have put it in having the stock 4-link. My issue with the 4-link is the side movement when/if bushings are worn. Not a pretty site or feel. All of this is my own personal opinion as well, but being in this business my entire life, it's pretty spot on.

[NAZ]

While we're discussing how to improve a Mustang style 4-link, the easiest way is turn it into an offset 3-link like FFR did. You still have limited adjustment and inefficient angled LCAs but you've eliminated the binding of the Mustang 4-link.

However, for me I wanted an even better rear suspension. One that would work great at the drag strip and could be easily converted to an offset 3-link for SCCA Solo in a matter of hours. So I designed an offset 4-link with way more adjustment than I will ever use and a watts link centering device that has 10" of roll center adjustment. The ride height can be adjusted independent of the spring preload and the roll center and instant centers can be adjusted independent of the ride height. Like everything I design, this suspension is stronger than it needs to be. It launches hard & runs straight and doesn't rely on stiff springs or an ARB to control body roll.

161902

[cgundermann]

While we're discussing how to improve a Mustang style 4-link, the easiest way is turn it into an offset 3-link like FFR did. You still have limited adjustment and inefficient angled LCAs but you've eliminated the binding of the Mustang 4-link.

However, for me I wanted an even better rear suspension. One that would work great at the drag strip and could be easily converted to an offset 3-link for SCCA Solo in a matter of hours. So I designed an offset 4-link with way more adjustment than I will ever use and a watts link centering device that has 10" of roll center adjustment. The ride height can be adjusted independent of the spring preload and the roll center and instant centers can be adjusted independent of the ride height. Like everything I design, this suspension is stronger than it needs to be. It launches hard & runs straight and doesn't rely on stiff springs or an ARB to control body roll.

161902

Very, very trick - mad skills Naz! Love it...

Chris

[PG_Cobra]

I have a theory that what may be the issue with the Mustang upper control arms is that with side load and displacement, one arm angles longer and the other angles shorter.
Before I launched into a complete redesign, I would try a panhard bar to limit lateral displacement. A Watts linkage would be better, but more complex. I would use rod ends on the panhard, not soft bushings.
jim


I was thinking along these lines when I found this link on the Maximum Motorsports website. I installed their Panhard bar system to my 4 link as I have a muffler with my underfloor exhaust that precluded the use of the FF 3 link.
https://www.maximummotorsports.com/tech_rear_susp_panhard.aspx

[J R Jones]

PG Cobra, Well there you go. Did you experience before and after results?
BTW I agree with underfloor exhaust for all the practical reasons and I like the way it makes the body look. Lighter, more lithe.
jim

[PG_Cobra]

PG Cobra, Well there you go. Did you experience before and after results?
BTW I agree with underfloor exhaust for all the practical reasons and I like the way it makes the body look. Lighter, more lithe.
jim

Jim

I've had the car on the road for 19 years, so plenty of experience with a variety of suspension changes that I made. Right before the Panhard bar I had Autoweld UCAs with the Max Motorsports LCAs. The main issue that annoyed me was if I gunned it a little around a traffic circle I could feels the snap oversteer kick in and have to correct immediately. The after experience is that the only thing to notice is the absence of anything apart from a correctly performing suspension. No snap oversteer, cannot make it blip out sideways, etc. I had a 94 Mustang GT, then an 06 Mustang GT. I could feel the difference in the rear between those cars immediately. That's the same effect I got with the Panhard bar change. I've never experienced the FF 3 link but I would expect the same difference from 4 link to 3 link.

Peter

[RoadRacer]

One of the common problems I see with the solid rear axle set-ups is folks get wrapped around the axle trying to set a specific ride height based on some dubious recommendation with absolutely no regard to what angle the LCAs are at. I suspect there are a lot of cars with varying degrees of roll steer out there. Same thing happens to 4x4 vehicles people lift and then experience handling issues. You can minimize that ill handling effect by ensuring the LCAs are parallel to the ground and the farther away from the more roll steer you'll experience.

Ok it's time for me to dig into this with you NAZ. I've heard you say this before, but only today noticed that my LCA are FAR from level. I switched to Levy's heim-jointed LCA, not the funny cast dog-bone shaped stock ones so now it is SUPER obvious.

On level ground, my LCA are at 5deg. That 3-link support in the photo is level.

161936

Now, luckily (?) there are holes above the LCA that I can use that look to be almost perfect for level LCA. No idea now why I chose the lower not the upper holes originally. But my larger/taller tires have made the problem worse I suspect. Kinda dumb to ask the question, but should I move the LCA into the top hole and make them level?

Here's a shot from other side where you can see the upper hole.

161937

[NAZ]

The short answer is “probably” but for every adjustment you make on a suspension, there is more than one single effect. Not enough space here to cover a lot of detail so I’ll try to keep it simple. And for others following, this is specific to a solid rear axle car (or solid front axle for you Jeep, Ford, and Ram fans) with a 3-link or 4-link suspension, or trailing arms.

The LCAs control the wheelbase. They swing in an arc so as the suspension travels through bump and rebound, the wheelbase changes. No matter what angle the LCAs are on, if they both travel the same direction and the same amount, the wheelbase on each side stays constant, i.e., they both get longer or shorter by the same amount. The wheelbase is at the longest length when the LCAs are level with the ground. This is the neutral position as if the axle moves up or down from this position, the wheelbase gets shorter. The shortening effect is exponential, that’s why lifted Wranglers have way more roll & bump steer and why I say the farther from parallel to the ground the LCAs are, the more roll steer.

The trouble starts when the LCAs are at in incline and the two side do not travel the same direction or the same amount. I didn’t have a lot of time tonight but I did find one video that sort of explains this about halfway through. You can also demonstrate this for yourself with a broom handle. Here’s how: Hold a broom handle in your hands out in front of you like doing curls with your forearms parallel to the ground and the broom handle perfectly horizontal (neutral position). With your forearms parallel to the ground, lift the broom handle (that’s your solid rear axle) up and down by bending your elbows while keeping the broom handle horizontal. The distance from your body to the tips of the broom handle changes but the distance is the same for each tip. Now starting with your forearms in the neutral position, lift one side and lower the other side the same amount. Again, the distance from your body to the tips are equal. This simulates body roll. Now start with your forearms at a 45-eg to the ground simulating your LCAs at an extreme angle. Now once again, lift one side and lower the other the same amount. Notice that the broom handle is skewed – one side gets further away from your body and one gets closer. This is what happens when your LCAs are not parallel to the ground and you experience body roll or run over a pot hole with only one rear tire. The axle skews and acts like a forklift, the rear tires execute an uncommanded turn.
https://www.youtube.com/watch?v=NkBhjX40A60

Now, I haven’t covered how this affect instant center and anti-squat so I’ll leave you to research that for yourself.

[RoadRacer]

Everything is always “it depends” I get that.. but I’m gonna do it anyway :)

Thanks for the explanation, makes sense.

[Norm B]

James, the Mk IV manual says the lower holes in the axle control arm mounts give more traction for launch. I am willing to bet the 33 manual says the same thing and that is why you used them in the first place.

NAZ, your explanation of control arm geometry perfectly explained the issue I was having with the original soft suspension using the donor springs.

Norm

[tonywy]

Question, with a 4 link set up if I made my own panhard bar should it be at an angle or parallel to the axle housing.

[PG_Cobra]

Question, with a 4 link set up if I made my own panhard bar should it be at an angle or parallel to the axle housing.

Parallel. This minimizes the lateral movement from the Panhard Bar arc as the suspension moves.

[NAZ]

[QUOTE=Norm B;482659]James, the Mk IV manual says the lower holes in the axle control arm mounts give more traction for launch. I am willing to bet the 33 manual says the same thing and that is why you used them in the first place.

This is because moving to the lower hole raises the instant center and that may increase anti squat which helps to plant the rear tires harder. But the opposite affect happens on braking. It's important to understand how your suspension adjustments affect handling and performance.

161970

Those LCAs are what propels the car forward. They push the car forward on acceleration and pull the car when braking. They are being acted on by the rear axle, pushing when on the gas and pulling when on the brake. The UCA is doing just the opposite.

[CraigS]

Maybe 15 yrs ago I saw an article where one of the well known Mustang aftermarket suppliers did some experimenting w/ a 4 link. They built a piece of a Mustang rear body/frame on a wall about waist height. They duplicated the frame mount positions for a 4 link on that wall so they could attach 4 links and an empty axle housing which they supported in the center w/ an adjustable rod. They could move the axle through any range of travel they wanted either straight up and down or at an angle to simulate the car leaning in a turn. The primary idea was to find out what would be the best bushings re; cornering. They started at normal ride height w/ OEM arms w/ OEM rubber bushings and proceeded to simulate a turn. It worked kind of OK. Then they started replacing the rubber bushings, one type at a time, w/ all the popular upgraded bushings. When they got to the point where they had poly (like Energy Suspension uses) at both ends of all 4 links they had to work really hard to get the axle to lean. The final step was rod ends (or sphericals) in all the arms. At that point they could not get the axle to roll at all. Proof beyond a doubt that the OE 4 link relied on squishy rubber bushings to work. When I had my MkI w/ 4 link I talked to Gordon Levy & he recommended poly in the LCAs and OEM Mustang Cobra UCAs. He said that Ford used a slightly harder rubber in the Cobra models so it would help tame axle hop but still corner reasonably well.

[NiceGuyEddie]

162578

5-link!

25% better than 4-link.
66% better than 3-link.

;)

[CraigS]

A thought re; ride. On a solid axle car, if you go to coil overs, the ride on a straight road going over normal bumps will be the same w/ 3 link or 4 link (as long as the 4 link has relatively soft bushings). Re; handling corners. A 4 link can be made to be a reasonable handler as long as you stay w/ rubber bushings. Install a front swaybar and no rear bar. Although I went to a 3 link on my MkI and my MkII, the idea of adding a panhard bar to a 4 link is a good one and again stay w/ rubber bushings in the 4 links but rod ends in the panhard. The one remaining downfall of the 4 link is that staying w/ rubber bushings leaves you with axle hop. While you can train yourself to drive around it and mostly avoid hop, for me, it is so much more fun being able to let the tires spin some.

[GTBradley]

I love a day when I truly learn something new. I'll admit, I bought the IRS to avoid all of this and have an all around good suspension, especially since I don't do drag racing or serious road racing.

This explanation by NAZ was very good for understanding the complexity of suspension geometry. One question though, if the control arm rotation causes an effective shortening and lengthening, wouldn't a rear mounted anti-sway bar help with this? And, is this also one of the reasons it's best to have the ASB parallel to the ground? I've noticed that the ASBs FFR sells for the front are angled down quite a bit, but Mike Forte's are level, as his mount in a different way.

[NAZ]

GT, an ARB (sway bar) will not change the way control arms swing in an arc, therefore, an ARB will not affect how the wheelbase changes when the control arms travel through their motion range. However, a rear mounted ARB will resist a solid axle rotating around a longitudinal center line and while doing so will reduce the amount of control arm movement due to roll. But ARBs increase spring rate which can affect traction so, once again, suspension adjustments usually affect more than one area. You can also reduce roll by raising the rear roll center and that doe not change spring rates.

Now, for the second part of the question dealing with ARB lever arm attitude. When the arms are perpendicular to the direction of suspension travel, the ARB has the least resistance to roll. So, on a typical solid axle car the suspension travel is fairly vertical in its movement so having the ARB lever arms parallel to the ground gives the most leverage to twist the ARB making the ARB seem softer. When the ARB lever arms are placed at an angle to the direction of suspension travel, the ARB has more roll resistance as the arms have less leverage making it more difficult to twist the bar. In effect, placing them at an angle is like shortening the lever arm.

I should have added that installing an ARB with the lever arms at an angle to the direction of suspension travel is not a tuning aid I'd recommend. I like to have the ARB arms perpendicular to the suspension travel when at ride height. That way when under body roll the arms travel in the same arc but opposite. If you want to adjust the ARB roll authority as tuning aid, you should do that by shortening or lengthening the arms, not by angling them. Three-piece ARBs usually have multiple holes to facilitate this adjustment. Some solid bars have more than one hole.

Hope all this makes sense.

[GTBradley]

Yes, very helpful. Unfortunately, Mike’s ARB does not come with instructions, so I did my best. I loaded my body weight in the drivers seat and then adjusted the front bar for no tension. Does that sound appropriate?

To the OP, sorry for the temporary post highjack.

[J R Jones]

NAZ, you took on the task, good job. GTB's question about "control arms" and IRS confuses the reality of the original live axle (four bar) issue. Brad may be confused.
The upper two of four bars are angled, narrow pivots in front and wider pivots in back. With high yaw loads (aircraft term Brad) the live axle makes one upper bar displace longer and the other upper bar displaces shorter.
This causes wheelbase disparity and tries to twist the axle. The simple single upper bar merely pitches (more aircraft) the axle down in front, because the lower links are longer. Tolerable.
My much earlier band aid suggestion was a panhard bar or watts link to restrain the live axle from yaw relative to the chassis.

[NAZ]

GT, if you're talking about Mike's front sway bar for the roadster you should give him call and discuss how he intended it to be set-up.

What I would expect is that at ride height the arms would be parallel to the ground and there would be no twisting load on the bar. The links are adjustable. On a street car, I expect your ride height is set-up equal side to side.

[GTBradley]

Thanks for dumbing it down to pilot language, JR. Ya know, they say a pilot’s intelligence is squared by the distance from the controls and the loose nut behind the yoke and all.:)

Naz, I found enough info from others, namely Jon (nucjd19) on his post Forte Sway Bar Kit (https://thefactoryfiveforum.com/showthread.php?41704-Forte-Sway-Bar-kit) and Mike’s pictures on his website to get it installed correctly. I’m just concerned with how to adjust it now. I’ll do a separate thread in that.

[J R Jones]

Brad, As NAZ has suggested flat ARB arm angle is preferred because the spring rate will be the same from flat up as from flat down. If your static arm position is not flat, the up spring rate and down spring rate will not be the same.
No ARB link preload at static ride height is prefered, actually for the same reason.
jim

[GoDadGo]

The final step was rod ends (or sphericals) in all the arms. At that point they could not get the axle to roll at all. Proof beyond a doubt that the OE 4 link relied on squishy rubber bushings to work.

Wow, Craig!

I always thought the 4-Link Mustang suspension had "Interesting Geometry" but always assumed that it didn't bind.
If you can find that old article I'm sure everyone on the forum would want to read it.
I went with the 3-Link because of the simplicity of the design.
It has good articulation with very minimal moving parts.

Steve

NOTE:..A similar 3-Link was used on the Lincoln Continentals from 1975-1979.
.........I Really Miss Those Land Yachts That My Parents Cruised Around In!

[Joe Campbell]

https://www.youtube.com/watch?v=-ywdw16cZ-I
05-14 like that guy was driving has 3-link/panhard bar, but you can still get them into crowd-mowing spins if you work hard at being dumb enough. :)

I've had 3-link and IRS, 3-link can handle just as well on nice curvy roads, but on bumpy potholed roads, you really feel the rearend getting bounced around. IRS wins hands down when the roads are less than perfect, as they are on the funnest mountain passes around here.

[Joe Campbell]

Wow, Craig!
I always thought the 4-Link Mustang suspension had "Interesting Geometry" but always assumed that it didn't bind.
If you can find that old article I'm sure everyone on the forum would want to read it.

These folks explain it well, they make the best Mustang suspension upgrades out there. They explain how the angled upper 4-link arms are trying to do two jobs, and neither one well. Also the snap-bind phenomenon that helped earn Fox Mustangs their crowd-mowing reputation. https://www.maximummotorsports.com/tech_rear_susp_panhard.aspx
(I've fixed up countless Fox platform cars over the years, currently working on a pair of them in the garage. As flawed as they are, they feel like a pair of comfy old jeans to me... set up right, they can be almost as fun to drive as the FFR).