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March 31, 2011 9:53 a.m. ReverendDexter SuperDork

So, after everything, I've got some mad understeer going on in the Mustang ('90 5.0 'vert).

I love the torque arm, but it's go so much grip it's just overpowering the front end at this point. I'm not really sure what I can do to improve front end bite without dropping traction out back.

Up front I'm running SN95 spindles and MM CC plates, but I'm still maxing out for negative camber at under a degree (no, my plates aren't backwards). I probably need to replace the A-arm bushings (150k on the car and I think it still has the stock bushings/balljoints), but I don't really want to rip the A-arms out, as that just turns into a justification snowball where I end up ripping out the whole K-member and dropping in an Agent47 SLA.

I remember someone on here (Sorry, not good with names, but your avatar is a white SN95 Cobra) saying that foxbodies counterintuitively benefit from a larger swaybar up front when encountering understeer.

So, thoughts? Should I start just by replacing the bushings and balljoints and throw a camber bolt in my strut mount?

Is swapping to a tubular k-member and coil-overs the night/day difference up front that the torque-arm was out back?

Or do I just suck it up and save my pennies for a front end worth three times what the car is?
March 31, 2011 11:56 a.m. Maroon92 SuperDork

Coilovers, yes. Tubular front K can wait!

Give it MORE stiff in the rear (tee hee), and the front should calm down...or maybe it will just promote snap oversteer!
March 31, 2011 12:11 p.m. pres589 Dork

What spring rates and sway bars are on the car now? Front coilovers might be nice since you can play with height a bit for a little tuning.
March 31, 2011 12:12 p.m. ReverendDexter SuperDork

Curious how coilovers are going to improve things? Doesn't improve my geometry any. Not arguing; it just goes against my understanding of how the world works.

Rear springs are already stiff compared to the front. I'm running MM's torque arm springs out back, and their road&track springs up front with Bilstein HDs and stock swaybars.
March 31, 2011 12:22 p.m. pres589 Dork

Talked to MM about it? Perhaps the torque arm setup changes effective rates on the swaybar.
March 31, 2011 12:30 p.m. Apexcarver SuperDork

It was me with the front bar recommendation.

I am running a 35mm front bar on mine (ESP auto-x suspension setup is in the cars writeup) (22mm rear IIRC, but stock geometry)

As the car rolls you loose camber, so you are only using the outer edges of the tires. If you take tire temps I would bet that the inside fronts are stone cold while the outer edges are toasty. Especially with less than 1* of camber. Big front bar makes you use the tire by limiting roll and reducing camber loss.

I am not sure what putting the SN95 spindles did for your geometry (static camber wise), you may consider looking into SN95 arms. I am running off total foggy memory (I run an SN95, never messed with a Fox) but IIRC it gives you some camber. Research the effects of doing that.
March 31, 2011 12:40 p.m. The_Jed Reader
You could try slapping on some SN-95 A-arms (you would probably need an SN-95 rack too), that should net you a bit more negative camber and yield a much more favorable camber curve.

IIRC a decent spring-rate starting point for a Fox with a torque arm is around 750 lb/in front and 450 lb/in rear with stock sway bars and the springs in the stock locations.

IIRC #2: I believe the Fox ('87-'93 at least) steering axis inclination is 15.5 degrees and the SN-95 is 13.5 degrees, so unless I'm the victim of a complete synaptic miss fire, you should actually have MORE negative camber than you need.

IIRC#3: You may be encountering a toe issue as well. I seem to remember the amount of ackerman engineered into the spindles changing throughout the production run of the Fox/ SN-95 platform, increasing as the years went by. They did this by moving the steering "arms" (where the tie-rod attaches) of the spindles outward. This, if not compensated for, would give you excessive amounts of inward toe.
```
                   front of the car

                  I          I = Fox

                 \          / = SN-95

                 rear of the car
```
Then again, it has been several years since I've turned a wrench on a mustang, so I could be way off.
March 31, 2011 12:43 p.m. The_Jed Reader

I'm a slow typist, I was still typing when apexcarver posted. The SN-95 arms are 1" longer than Fox arms.
March 31, 2011 12:44 p.m. Duke SuperDork

Maroon92 wrote:

Give it MORE stiff in the rear (tee hee), and the front should calm down...or maybe it will just promote snap oversteer!

Not a 'stang expert here, but the camber-challenged BMWs definitely benefit from much beefier front sways. Although this does violate conventional wisdom, the increased roll control really helps avoid going to positive camber on the OF wheel under load. I imagine the Mustang might improve the same way.
March 31, 2011 12:56 p.m. ReverendDexter SuperDork

I actually just got an email from Jack at MM (had sent them an email yesterday evening).

According to him, with the up-to-'89 CC plates, I'm losing 1.1 degrees of camber over '90-'93 plates. The SN95 spindles are wider track width, but he says they're increasing the camber 1.7 degrees positive (counter-intuintutive to me, but it might actually make sense if they're compensating for the extra length of SN95 A-arms). Lastly, he mentioned that the bilsteins have a larger lower mount hole, and there's about 1.4 degrees of "wiggle room" (my term, not his) there.

So, that being said, if I do go to a larger front bar, should I increase the rear bar as well to keep things "matched"?