It's pretty well acknowledged that fox body suspension design has significant faults that takes time/effort/money to correct. We've also discussed here that despite the prolific use of Mustang II front suspensions in hotrods of all types that it wasn't all that great its self.
So which of these two are better, why, and how do they compare to the earlier Mustangs?
Finally! Something i'm knowledgeable about!
I worked at FatMan Fabrications for about two years and we made mustangII front ends for all kinds of cars. Ford was very slow making there suspensions better so they stayed around for a long time. First mustangs got the suspension from the falcon.
MustangII suspension was more or less "right" as far as geometry goes but the stamped lower arms and strut rods of the real mustangII front end is replaced with tubular lower control arms in the aftermarket. The best thing about the mustangII is it works with almost anything and there is a huge aftermarket. You want all stainless parts? You got it! What brakes do you want? Wilwood, brembo, bear, factory? What lug pattern? 5x4.5,4.75,5,5.5 6x5,5.5 or even an 8 lug! What about steering racks? Power manual fast slow? Then there is tons of information on setting these front ends to do anything you want as far as geometry goes. Oh and don't forget you can have any kind of spring/shock combo.
Then they went to the struts with the foxbody and that went from 78 and more or less stayed the same up until 04... Yes that long. Not much to say about this front end. I had a 01 Mustang stock and it was ok, didn't pay it much attention because the rear end of that car was so bad. The rear end of the foxbody was so bad they added a extra set of shocks to keep if from moving forward and back on the car. Iv heard all you need is new lower control arms to fix that issue though.
Oh but one good thing about the foxbody is that the rear suspension more or less stayed the same all the way until 04 so that means you can fit the cobra IRS in a foxbody pretty easily.
In reply to Skervey:
So the Foxbody front suspension truly was a step backwards from the Mustang II, not just in design but also function? That's what I'd been curious about.
The Fox body front suspension is basically a MacPherson Strut suspension so many of the "fixes" that have been developed to make this design of suspension "work" will work on the Fox.
Don't lower it to much, add camber, add caster, firmer bushings, etc.
As for the rear on a Fox most serious owners have just tossed it in favor of a torque arm/panhard bar set up or a 3 link. There are a few other options using modified stock parts as well.
I owned 3 Fox Mustangs and road raced one of them. They are not "sports cars" but a shortened Ford Fairmont. When they came out they were considered good handling cars. Ford just kept the design around 10 years to long, maybe 15 years? Whatever!
It's still a good platform to start from if you have time and the skills to modify the car to make it do what you want. Much of the "work" is already done by others so you don't have to guess at what works and what doesn't.
I faced the same issue when I started to road race a VW Scriocco II 16V. It's a Mk I VW so what it takes to make it handle was as easy as turning on my computer and searching.
I autocrossed a '96 mustang for a while. The front mcstrut needs the usual mcstrut fixes to battle the lousy camber curve. The factory four link rear is a mess. I went with what they call a "poor mans" three link. I removed the upper left control arm and added the Fays 2 watts link. The rear of the car seemed much more stable and predictable afterwards. Basically had $700 bucks in the rear. Worked for me.
Good thing is there is huge aftermarket available, pretty much can fix all the shortcomings of the chassis.
The front on a Fox (SN95 being basically the same but with some improvements trickling in over the years) is the previously mentioned poor camber curve along with bumpsteer issues and I believe minimal to zero designed-in Ackerman. The bumpsteer can be helped with adjustable height tie-rod ends. I don't know how to correct for the lack of Ackerman.
I think the Fox's front suspension was cheaper to produce and more compact from a width standpoint compared to the SLA-style MII suspension. It's also taller.
I kind of think it would be easier to band-aid the issues with the MII's rear leaf springs than the convoluted four-link on the Fox. Out of the two I think a Watts or Panhard link would assist the Fox more than the MII. They both suffer from axle wrap and I don't know if either of the rears have much anti-dive designed in. The aftermarket has some proven solutions for the Fox. Probably a lot of solutions that are chassis agnostic work on an MII. A lot of higher powered Fox based Mustangs will tear the chassis around the rear suspension mounting points as the suspension really is in constant bind. In younger days peers would say it was because the cars were "so powerful" but I always felt like it was because they were "not well designed".
Out of curiosity, why do I see lots of folks fixing the rear suspension rather than bolting the cobra IRS in?
pres589 wrote: I don't know how to correct for the lack of Ackerman.
Move the steering rack fore/aft, maybe with some steering rack mount spacers.
In reply to thatsnowinnebago:
The Cobra IRS isn't cheap in and of itself and it wasn't actually that great out of the box. There's actual a GRM article about a guy that was road racing an IRS Cobra and went faster after talking to Griggs Racing and they talked him into installing a bunch of their parts and a solid rear axle. Car went faster. Maximum Motorsports says they have figured out the issues with the Cobra IRS and can make it worth working with (I don't know what the fixes are off the top of my head). The Cobra IRS was made to swap into a chassis originally developed in the late 1970's; "contrived" is probably an accurate label as to how that all went.
thatsnowinnebago wrote: Out of curiosity, why do I see lots of folks fixing the rear suspension rather than bolting the cobra IRS in?
I think cost and availability are the primary hurdles of a Cobra IRS swap. A full IRS typically runs $1200-1500. A bushing kit to alleviate the wheel hop and looseness costs several hundred more dollars. Coilovers or aftermarket springs cost more on top of that. If you're feeling spendy, you can call Kenny Brown for revised tubular control arms and fancy coilovers but they're stupid money.
And there just aren't a ton of IRS assemblies out there. Basically every Mustang from the dawn of time has had a stick axle. They've mostly gotten them figured out, and there's more info out there on how to make them work than there is for the IRS setup.
GameboyRMH wrote:pres589 wrote: I don't know how to correct for the lack of Ackerman.Move the steering rack fore/aft, maybe with some steering rack mount spacers.
Moving the rack shouldn't effect ackerman, if anything it will add bump-steer.
We used to cut the steering arm off the foxbody spindles and add our own to keep the steering joint on the ackerman line.
I don't understand how you can add more ackerman? Its either right or wrong correct? Toss a string from the center of your rear axle to the pivot point of your front spindle and if the center of the steering arm doesn't fall on the line then its wrong and you need to get it on the line to make it correct.
Skervey wrote: Moving the rack shouldn't effect ackerman, if anything it will add bump-steer.
It will affect bump steer but also Ackermann, technically in part due to a slight change to the tie rod length - you'll have to retract or extend both rods slightly to fix the alignment after moving the rack.
The "proper" way to fix Ackermann is to change the length of the rods AND the rack while leaving the rack in an ideal position to minimize bump steer ("in line"), but in practice changing rack length is a monstrous PITA unless you're a well-funded race team, so nobody does it this way with production cars. In practice, you can often find a decent compromise where Ackermann is improved while bump steer is only slightly negatively affected, or sometimes even improved.
Ah, pricy + not good. Makes sense why most folks stick with the solid axle now.
In reply to STM317:
Fun fact is getting a torque arm and watts link under a Mustang seems to be just as expensive as getting an IRS and then getting the thing working. That was how it felt when I owned my SN95; they're cheap to run but to really make right costs money just like any other car. In retrospect I wish I had picked up an E36 BMW But that's dragging this thread away from its original intent.
GameboyRMH wrote:Skervey wrote: Moving the rack shouldn't effect ackerman, if anything it will add bump-steer.It will affect bump steer but also Ackermann, technically in part due to a slight change to the tie rod length - you'll have to retract or extend both rods slightly to fix the alignment after moving the rack. The "proper" way to fix Ackermann is to change the length of the rods AND the rack while leaving the rack in an ideal position to minimize bump steer ("in line"), but in practice changing rack length is a monstrous PITA unless you're a well-funded race team, so nobody does it this way with production cars. In practice, you can often find a decent compromise where Ackermann is improved while bump steer is only slightly negatively affected, or sometimes even improved.
Seems a bit different from how iv come I understand it. Ans you guys have a lot more exsprince with this and I love to learn really technical stuff like this!
Iv always known that where the rack is located is the effect in bump steer, Ex the rack needs to be the same level as the pivot point in the upward travel. The as far as moving the rack forward and back in the car im a bit fuzzy I would think that you would need the rack the same distance back as the the tie rod goes into the spindle.
They way I know it is that the only thing that affects ackermann is where the tie rod goes into the spindle as compared to the ball joint.
Ex.
That's true for drag-link steering as seen in the diagram, but rack-and-pinion steering has 3 moving pieces in place of the single solid tie rod and the geometry for R&P is much more complex.
Oh man that's going to be a fun read! Hey thanks for the link!
Oh and talking about whatts link rear end mustang makes me think about speed academy. They are building a later model mustang for track use. Fun to watch there show on youtube.
pres589 wrote: I think the Fox's front suspension was cheaper to produce and more compact from a width standpoint compared to the SLA-style MII suspension. It's also taller.
Actually the fox platform was one of the first to have the engines installed on the assembly line from underneath, so the MacPherson strut front suspension can easily be installed on the engine cradle/k-member to go up all as one unit. Definitely cheaper that way.
Has GRM done the article on Bret's CAM Championship Modzilla (99 Roush) yet?
He's spent a few years and quite a few $ in figuring out how to get a Fox to handle.
The Fox chassis originated with the 1978 Fairmont. It was, typically for '70's Detroit, designed for lowest cost first and foremost.
With the proper application of money, one can get a Fox Chassis car (Fairmont, in this case) to make poorly driven Corvettes to wonder what the berkeley is going on. It would be even better if I would add some brake ducting.
Also, I'd love to figure out how to get some Ackerman.
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