bad handling, some body rot


New Member
May 20, 2007
New York City
I'm a frequent (daily?) lurker and a rare poster... but some advice would be really appreciated. I am being wordy, but I want to save you from having to ask for these details.

My issue: Frankly, the handling has been scary at times, feeling like the back of the car wants to rotate. I'm just driving it around town, on the highways, nothing crazy.

Some history: I've been driving my '69 sportsroof for almost ten years, but only 25,000 miles in that time. I started this car when I was a 13 year old kid, so I probably put some parts on that I wouldn't have used today. Age of some of the parts may be at issue, as may be some rust that has come back or gotten worse.

Here is my setup:
-progressive coil springs: don't remember the rating, it was years ago.
-KYBs all around. Yeah, the cheap and hard ones.
-rear leafs probably are of the 'heavy duty' type.
-power steering, manual drums all around
-Shelby drop w/ wedge. I'd have to measure if it is the standard 1" drop.
-alignment to the performance specs (not Ford's specs)
-Ford export brace and a monte carlo bar
-16x8's all around with 225/50 in front and 245/50 out back.
-the car sits a little bit higher in the front. Always has. Driver's side might be a little lower than the passenger side (big clue?).
-stock front sway bar
-all suspension was redone less than 20,000 miles ago, but I did replace a loose right side LCA and ball joint last year.
-the car rides hard, potholes are jarring and I've bounced into the next lane when hitting bad bumps at highway speeds.

-towers look OK but have the common rot at the "shelf" or base.
-inner rockers on both sides have rotted through bc of my leaky cowl. I just found this when I pulled my carpet last summer.
-both torque boxes have their typical rot.
-floors good
-rear frame, where the shackles bolt on have their rot as well.

My gut tells me that there is a lot of east coast rot that is resulting in a soft body that may be out of spec or flexing at some critical points, like where the leaf shackles attach. Also, the springs and shocks may not be a good setup for street driving.

This summer I plan to do some serious work on the car but want to prioritize. I'm thinking to tighten up the body before changing too many parts. Fix all the rot, add subframe connectors. If I have the cash, I may change for softer springs and beefier sway bar in front, roller perches, softer shocks (edelbrock, unless you recommend a cheaper alternative).

Last question: Anyone have a chart with body measurements for me to check that my body isn't too far from spec?

Thanks again.. pix at
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That's a nice looking Mach. I'm looking for a '69 Mach I for my next project but the last one I looked was full of rust too.

If your rear shackles are attached to a rusty subframe I wouldn't drive the car again until replacing the rotted metal. Same goes for shock towers. As I'm sure you know these areas take all of the cornering forces and should one fail under load you will lose control. The torque boxes, inner rockers and subframes distribute the load through the unibody so if they're shot you have wet noodle for a chassis. There is nothing you can do to the suspension to help the handling if the metal has lost it's integrity.

Fix the rot first. Add subframe connectors. I think your suspension choices are ok even if they are a little hard. With a sturdy chassis and those parts it should handle very well on all but the bumpiest roads.
Nice looking car and I salute you for driving it regularly! We really need some pictures of the body rot to get a better idea of what you're up against. However you've already formulated a plan of attack and I think once you start tearing into it you'll have a lot more questions. If the body is lower on one side then either one of your leafs is broken or your frame has collapsed on that side. A broken leaf would explain the rear end trying to come around. Anyways good luck and keep up updated!

Last question: Anyone have a chart with body measurements for me to check that my body isn't too far from spec?

This should help you out. You can find tons of info like this specific to your car at

Good luck with your project!

I have seen cars in much worse shape than yours appears to be in that still handle ok (I have one now). Unless someone went to a lot of trouble to keep the car a looker despiste major body rot (mine starts to fall into this category), I don't think body rot is causing your problems.

Look into the suspension before you blame it on body rot.

Now, don't get me wrong, fixing body rot it always important (and a never ending battle for some of us). Like posted earlier, some good pictures of your underbody, frame, and "roting" spots would be very helpful.

Hah, my friend with a 68 convertible says my car is tons more solid than his. I'll take some photos over the weekend and post 'em up. I remember driving my car with more confidence when I finished it about ten years ago.

The rot has to be fixed anyway, so I'll see what happens to the handling once all is fixed. I do most work on the car but I haven't learned to weld yet and I don't have a place to do big jobs. The garage is valet, under a 30+ story building in Queens, NY. I'm going to have to pay someone to do the repairs, but the guy I may use would let me get under there and do as much as I am able to. Stripping, paint, etc. I'm afraid to be looking at a big sum of cash for the torque boxes, rear frame patching, etc. Yeah, my cowl leaks, but my solution is not to get the car wet anymore.

I get a lot of satisfaction out of driving the car as much as I do and its pretty cool to be driving a 69 mustang. Mean looking car. In all my years of driving it, however, I've never passed another one on the road unless going to or coming from a car show.

I'll post updates and thanks for the welcome. I'm on 69.stang as well, postings not as frequent as this forum.

Finally, I found this image, with body dimensions for a Falcon. Anyone have something similar for the '69 stang?


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I'm looking at some pix and I think the ball joint wedge on the UCA may be contributing to the nose up stance of my car. It was made to prevent binding, but I've recently read that the wedge may not be needed if you don't do too much of the Shelby drop. Any feedback on that?
I'm looking at some pix and I think the ball joint wedge on the UCA may be contributing to the nose up stance of my car. It was made to prevent binding, but I've recently read that the wedge may not be needed if you don't do too much of the Shelby drop. Any feedback on that?

From what I understand you don't need the wedge if your Shelby drop is only 1".

UCA drop misnomers

“ALL UCA drops, regardless of dropped distance, require the use of a negative wedge kit.”
- The negative wedge kit is not required on drops of 1” or less. The 1” UCA drop causes the upper ball joint to extent to a position near its max tolerance, however, it does not overextend the ball joint. A negative wedge kit repositions the angle of the ball joint and increases ball joint range. By increasing ball joint range, a negative wedge kit allows you to lower the UCA up to a full 1 & 3/4” from the stock location, which is the point that creates the most ideal camber curve. IF YOU LOWER THE UCA MORE THAN 1” YOU MUST USE A NEGATIVE WEDGE KIT!!! If you do not, the UCA ball joint will be extended past its designed range of motion and separate, which will cause suspension failure and possibly an accident. Something to consider before investing in a negative wedge kit is that the benefit of UCA drops of more than 1” are minimally more effective than the standard 1” drop. What I mean to say is that the difference between a 1” drop and a drop of 1 & 3/4” is negligible. Many people who have purchased the negative wedge kit and lowered the UCA more than 1”point out that the difference between the 1" and 1 & 3/4" drop is too difficult to see on the street and not worth the money, in their opinion, for street cars. IMHO, the only time the 1 & ¾” drop is worth the time, effort and or cost, is when the car has been built for the circle track. If you want to purchase a 1 & 3/4" UCA drop templace go to Opentracker Racing Products

“Doing the UCA drop actually lowers the ride height of the car 1 inch.”
- Although the upper control arms are lowered one inch, your Mustang's ride height will not sit one inch lower in the front. I noticed about ¼” drop on both of my Mustangs from this modification after the suspension settled, and ride height changes between ¼” and 5/8” have been reported by others who have done this modification. The reason this modification does not lower the car a full 1” is that ride height is determined by the spring and shock and the relative height where the spring and shock attach to the UCA. The ball joint end of the UCA rests at a fixed height to the road and the spring assembly is, of course, positioned in the middle of the UCA between the fixed ball joint end and the lowered end. Since the height of the UCA relative to the road remains the same on one end and changes on the other, the actual drop of the car is somewhere between the two changes of 0” and 1”. Thus, the drop is less than 1”.

Good sites for more info on this is:
I'm looking at some pix and I think the ball joint wedge on the UCA may be contributing to the nose up stance of my car. It was made to prevent binding, but I've recently read that the wedge may not be needed if you don't do too much of the Shelby drop. Any feedback on that?

It's true that Shelby limited the UCA relocation to 1" to avoid ball joint bind - but the negative wedges do position the joints nearer the centers of their range of movement. I've never heard of the wedges making the front end *higher*... where did you see that info? Most write-ups do mention that the relocation + wedges will lower the ride height by less than one inch.

BTW, you mentioned having progressive-rate coils up front. How is their transition from "comfort" to "performance" spring rate?

I concur with those above who recommend fixing the rot. Replace the rear frame extensions if necessary, it's not that tough of a job. Check the front attachment points for the leaf springs, make sure those are sound (most subframe connectors attach there). If you don't want to cut the shock towers completely out, weld in those lower patch pieces to make sure the suspension mounting points are as rigid as possible. I think I'd put the subs in before dealing with the inner rockers and front torque boxes, but others here may have different opinions.

The subframe connectors that extend out and attach to the rockers might be overkill, but they look stout as Hell.
Thank you Pak

Yeah, I only saw a little "x" where the picture should be. I'll check out my car on Sunday and shoot some photos. Good idea to put on the subframe connectors before cutting things off.

Regarding the progressive coils.. I've only known my car after all the listed parts were on, so I've no idea what the car would've driven like beforehand. I can't say I notice any transition from the lower to higher spring rates. The car is always stiff and level with zero body lean.
without putting too much thought into it, I was thinking the thickness of the wedge itself is lowering the point of attachment of the spindle to the UCA (at the outside edge, the wedge is around 1/2"), thereby raising the body of the car a tad more. So.. if I wanted to lower the front, I'd be cutting more coil (and raising spring rate) more than if I didn't have the wedge. I'll also check the coil insulator on top. I remember it is poly, and I was toying with a couple different thicknesses. This was over ten years ago. Though, if I lower the front end, I'll look at the lowering coils.
Photos are up

Here are two ugly photos. First is the driver's side rear frame rail where the rear leaf shackle bolts on. Not much metal left. Probably not safe to drive, huh?

Next is the passenger side torque box. The rail looks holey, as well.
Note, the inner rockers are rusted through on passenger and driver side. The photos can be seen by clicking on the link below.

Please take a look at the rest of the photos from underneath at my website. Rust photos are on pages 3 and 4 in my mustang gallery. I'd appreciate some feedback, encouragement, advice.


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Did you buy the wedge kit and the springs from the same guy?

You say the car "rides hard". Meaning, if you hit a small bump or hole, the suspension is so stiff it just pounds it getting you sideways or do you mean it's so stiff that hitting expansion joints on the freeway cause you to get sideways?

Is the car hard to drive over bumps or railroad tracks?

In a straight line?

In corners?

In left and right hand turns?

Under power (acceleration)? Braking? Steady cruise?
I bought the wedge kit over 10 years ago from Promotorsports, I think? It came with the wedge, metal drilling template and hardened UCA ball joints.

The ride is stiff, but the car is stable in a straight line. Small bumps don't unsettle the car so much. Its the bigger stuff, at highways speeds that get the car hopping to the next lane. Around town, I avoid potholes, of course, and the handling is fine at low speeds.

My complaint is when taking sweeping curves, like highway exit/entrance ramps or curvy highways. If I don't take it really easy, the car feels like the rear wants to come around. Its not snap oversteer, and I haven't pushed it hard enough to do so, but I feel the car kinda wanting to come around. Its unsettling because I'd like to feel more confident pushing the car around.

From my photos, I clearly see the driver's side leaf spring rear shackle is barely hanging on to the frame rail. That could be the problem.
I'd fix the rot first, then loose the stock sway bar. I don't know what 69's have but earlier years came with 5/8" that didn't do much.

It does sound like your leafs are shot, or you do have something getting loose back there though. A lot of people will say don't use a rear sway bar, but I like them. Fix the obvious problems first though.

The KYBs are what's making your ride harsh.
Your (front) PMS springs are fine. They are softer than the 620's most folks run. I have them and use them.

The front shocks are fine. They are valved a little stiff but they are OK. The rears flat s_ck. They are way too stiff. I like the Bilsten ones from Maier (they seem to be the best of the bunch outside of Penskes) but the GR-II or anything else except for the Koni's will be an improvment.

Your front swaybar is too little. If you want the pimpy pimpy one, buy the BIG one from Cobra Automotive. Either the 1" or 1 1/8" aftermarket ones that NPD or others sell is fine.

I think a combo of a overvalved rear shock and too small of a swaybar are the cluprit. I'd change the front bar first. It'll be the cheapest mod you can make. You may be able to not do the shocks if it fixes it.

If you were closer, I'd let you borrow my 1" bar and try it. I'm getting the Cobra one.