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Discussion Starter #1 (Edited)
These classic cars have very poor handling (yet this is my experience).

The car (1st gen. 1967) drives okay on a plain pavement, but as soon as it gets to uneven, old pavement with potholes, driving becomes scary - i.e. it just does not keep track, it unpredictably makes turns.

Does anyone know where this imbalance in suspension could originate from? I am sure it is not the steering - it did the same with manual steering box, same with rack&pinion based on J-car rack. Just is unable to keep track, with small or high caster or any front wheel alignment.

Even old CJ7 (jeep) with even greater preconditions for bumsteer, solid front axles, lifted suspension and 35" tires is much more stable on uneven pavements. Anyone?
 

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Give a list of everything that is new and how old the parts are and what kind of tires and wheels? What is your current alignment settings? My Mustangs drive great but it was after repairing worn parts and doing alignments myself.
 

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Discussion Starter #4
- it has all the bushing new (less than 1000 mi) - strut rod, sway bar, leaf springs, motor mounts, t5 has oe mount but it's good
- then new kyb gas shocks, new K3601 control arms, new upper ball joints, upper arms are originals, tie rod ends too but they are tight
- 235/50 rear, 225/40 front Pirelli tires, 17" rims

As I said the car drives perfectly on flat pavement, but as soon as I get to bumpy section e.g. poorly maintained bridge, the car becomes very difficult to control, i.e. accidentally jumps 1-2 feet to the side, I also suspected worn parts and replaced nearly everything. I think this is matter of poor suspension design. Could this originate from rear end? Or change of camber that momentarily happens after hitting a pothole? What is more likely? What mod it is best to do first? (Shelby drop is not possible - I have too big wheels for that)
I keep .5° negative camber, caster +3°, toe in roughly 1/8" (I double checked the toe).
 

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Did you replace the strut rod bushings? If so what kind of bushing and did you make sure the preload spacer was installed?
 

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You didn't say if you have the export brace installed with a monte carlo bar also frame connectors help a great deal to stiffen these cars up. Our Mach1 used to jump around on a bumpy road but after adding frame connectors and new front bushings and a bigger stabilizer bar it tracks and hugs thr road like a new car.
 

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Discussion Starter #7
It has strut bushing kit from VA classic (they have installation guide too posted on web that I used). It has also diy MC bar made of 1/2" thick wall tubing. Stock sway bar.
On CJ7, I drive with no sway bar, and it goes straight through bumpy sections much easier than mustang, do you think than replacing mustang's stock bar with a thicker one will make noticeable improvement?
 

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First a good shock tower brace and monte carlo bar and subframe bars are necessary before you increase anti roll bar (ARB) stiffness. ARB's react all forces through the two frame rails - so there are two springs in the system, the ARB, and the frame itself. If the frame is not significantly stiffer than the bar, your improvement is going to be very marginal because the chassis itself just flexes more as you increase ARB stiffness.

For the physics minded, you have two springs in series (connected together,) which means a change in spring rate of one (the ARB) doesn't make the system stiffer by that amount, but rather by the inverse of the sum of the inverses (this is called compliance, 1/spring rate) kind of like resistors in parallel/series. In other words, the least stiff member has the largest impact on the overall stiffness.

For subframe connectors, the front roll stiffness is affected by the stiffness of the chassis in torsion front to rear as well - the stiffer the middle of the car, the more "disconnected" the front and rear suspensions are in terms of roll rates. Since the front suspension does all the work, you have to transfer body roll through the chassis. A more compliant one acts as another spring in the system, making induced roll take longer so your rear is lagging behind the front, making it "dart."
 

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The darting is the result of the alignment changing due to stress on parts that don't hold the alignment in the bumps. Assuming you have new parts then it comes back to alignment specs and whether the new parts were installed correctly. I have seen many people replace the strut bar bushings and leave out the preload spacer. The spacer slides over the rod and fits between the two rubber bushings. Is the spacer there and are the nuts that squeeze the bushings together very tight?
 

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Just to add that it is not a bad design. A good condition classic Mustang should handle nearly as well as a newer RWD car in normal driving (including bumps) if everything is fresh, properly installed, and properly aligned. It does not require modifications to do this, but modifications can improve handling even more. Darting is not typical for this design. Questions:

  • You replaced "nearly everything". What was not replaced?
  • Answer Arnold's question.
  • Monte Carlo bar is 1/2" diameter, or 1/2" wall?
  • Have you inspected the frame torque boxes for integrity?
  • Is your export brace 1-piece or 2-piece?
David
 

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My Falcon would jerk from one side to another while going in a straight line. Or trying to go in a straight line. Smooth road.

It had been in a wreck. Drivers side shock tower was pushed back. Also found the LCA mounting point would flex .

It would not hold alignment from one drive to the next. When you would start to drive the tires would toe out and it would start to jerk back and forth. With two grown adults sitting in the front, it was fine though.
Talk about weird, my buddy didn't believe me but he wouldn't drive the car alone either. LOL

I discovered the LCA mounting point issue while taking the front suspension apart for a Mustang II kit install.

Drives great now.

If you have replaced everything. look for signs of damage, crash or rust.

Jet
 

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Discussion Starter #12
Just to add ...
David
You replaced "nearly everything". What was not replaced? See my post above, it lists what was replaced and what was not replaced.

Answer Arnold's question... See the guide at http://www.virginiaclassicmustang.com/howto/instructions/su10.pdf
(The spacer is installed as instructed.)

Monte Carlo bar is 1/2" diameter, or 1/2" wall? 1/2" ID + 2 * 3/16" thick tubing = 1/2+3/8=7/8" OD

Have you inspected the frame torque boxes for integrity? No, + there is only driver side box.

Is your export brace 1-piece or 2-piece? it's actualy 3 piece, all tube braces (no sheet metal).

Mustang II front was a great improvement of falcon chassis
 

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Is it holding alignment?


You replaced "nearly everything". What was not replaced? See my post above, it lists what was replaced and what was not replaced.

Answer Arnold's question... See the guide at http://www.virginiaclassicmustang.com/howto/instructions/su10.pdf
(The spacer is installed as instructed.)

Monte Carlo bar is 1/2" diameter, or 1/2" wall? 1/2" ID + 2 * 3/16" thick tubing = 1/2+3/8=7/8" OD

Have you inspected the frame torque boxes for integrity? No, + there is only driver side box.

Is your export brace 1-piece or 2-piece? it's actualy 3 piece, all tube braces (no sheet metal).

Mustang II front was a great improvement of falcon chassis
 

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Have you inspected the frame torque boxes for integrity? No, + there is only driver side box.
...
Mustang II front was a great improvement of falcon chassis
The inspection would include the rear boxes and rear suspension as well. The rear suspension plays a very strong role in steering. True, in '67 the fastbacks and couples only got one torque box. Convertibles had two. In '68 they all had two from then on. Adding the second torque box will help with chassis flexing and improved handling. Also, your shock towers should be closely inspected for cracking - a common problem in the earlier years. This will cause erratic handling. Shock tower reinforcements were added later just to address this problem. You may want to consider adding them to yours, especially if yours are cracked.

Also, while not making an argument off-topic, I disagree that the MII suspension and steering are a "great improvement". It is different - not better - assuming both systems are completely fresh and properly aligned. If you analyze the differences, you'll find there is not much of any improvement in geometry, and some aspects are worse. What you do get is a change of coil spring mount location, support from the lower A-arm, and simplified R&P steering. None of those substantially affect the overall geometry of the system.

The reason the MII (and variations) is popular is to replace the shock towers and steering gearbox for more engine compartment space, the availability of dropped spindles for lowering, and stock disc brake systems. If needing to rebuild and upgrade a stock Falcon-chassis system anyway, the additional expense is easily justified in some cases. But, not because it is a substantial improvement in other ways. When a worn-out, sloppy and mis-aligned stock system is replaced with a new MII setup, the difference is very noticeable. Well, of course it is. So too would an all-new stock setup, especially if modified to improve it's known deficiencies.

As I said, this is not an argument, and anyone is welcome to disagree - but please be specific to what you disagree with and why.

David
 

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Discussion Starter #15
M2 has IMO more robust design of the front end.
It is not sufficient argument for falcons that their suspensions are as good as M2 although falcons' quality (i.e. how the car steer) changes with miles driven eventually causing cracking of structural components. Falcons have also incorrectly angled upper A arms which causes some bumpsteer, M2 has this fixed.
 

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I won't get into the better design coflict.

I'm happy with both of my cars, The Fairlane had all new bushings and balljoints with Granada disc, it drove ok. It didn't wan't to return to center very well. And I wasn't happy with the braking, panic stops were a panic. LOL!

The Falcon was a mess as stated above, We added 1/8" plate all around and as far back as we could to add strength back from the crash damage, subframe connectors.

I was already to deep into the car not to make it road worthy, paid to much for it in the first place. If your ever in South Jersey around Cobbs garage, steer clear of Norm. All I'm going to say.

But, Both cars drive great. Like night and day from what they were before.
I'm sure the Fairlane was probably a good allignment away from being right, but I also hated working around the Shock towers.

Just my .02

Jet
 

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Again, my intent is not to argue "which is better". I never mentioned that. I will say again, the MII is not a "great improvement". The point being, a good condition stock '67 steering and suspension setup should provide more than adequate service, and certainly no jerkiness on bumpy roads as described. A modified stock '67 suspension would be even better.

Either way, I do not agree with any indication that re-fitting with stock-style MII suspension is a cure for a stock '67 with basic driving problems. I have seen too many folks spend $2000 to over $3000 for very little if any street-driving improvement over a solid and well-adjusted Falcon-style setup. I do not want anyone reading this to get the idea that they should spend that kind of money just to fix worn or sloppy steering, old collision or stress damage, or even a simple mis-alignment. Ask SCCA Mustang, Shelby, Cougar and Falcon drivers (stock-style suspension) if they would or should have any issue with handling under any normal street conditions.

67gtman, if you want to swap to MII suspension, then by all means do so. If done properly with modern upgraded versions of MII parts it certainly won't be worse on the street. But, I hope you're not trying to indicate it is preferable or even necessary in order to get a good-handling and well-mannered '67 Mustang/Shelby/Cougar/Falcon.

David
 

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Discussion Starter #19
No no I am not going to install m2 front into falcon and I've never said that; just someone started to talk about m2 front and I said it is an improvement compared to falcons, maybe not "great" yet the m2 suspension is more like in many sport cars that drive 150-200 mph without any problems. I would like to see those shelbys & boss driving this fast
No idler arm now (rack steers)
 

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I'm following this thread and would like to know if you have found a fault for this problem yet?

I am confused regarding some of the information that has been posted please clear up...

1) Your car is a 1967 GT fastback yes or no.

2) Your car only has one torque box in the front? (Note; SBs came this way but I thought GTs and BBs had two? Well, I know BBs had two, not sure about GTs)

3) You have a rack and pinion steering system now?
 
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