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Requesting Stock Suspension Measurements 67-68 for Roll Center Calculation

3K views 32 replies 7 participants last post by  7T02S 
#1 ·
Hey everyone,

I was hoping that I could get a few of you to post some suspension height numbers for stock (or close to stock) 67 and 68 suspensions. What I'm looking for are some numbers from some relatively stock mustang, although a modified car would be great too if I know the modifications.

What I'm looking for are, with properly inflated tires:
  1. Tire size
  2. Height of lower inner control arm pivot bolt center to the ground. This is the one with the eccentric.
  3. Rough height of lower outer ball joint to ground.
  4. Height of the front of the rocker's pinch weld to ground, just forward of the front notch.
  5. Whether your car has the arning/shelby drop.
  6. List of any front suspension modifications, if any.
  7. Engine
I'm have the dimensions of the stock geometry into a suspension calculator (vsusp) but am missing the main height of some of the parts to the ground, so don't know where I'm starting from before making some modifications. My car is in so many pieces it's not funny, so I can't take any measurements.

Also, if anyone has accurate dimensions of the spindles, such as ball joint center x and y coordinates relative to the hub, I'd appreciate those too!

Thanks in advance!
 
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#5 ·
I found that I can enter in all the dimensions I have but if you don't know the starting point of tire size and ride height at inner LCA bolt, it's hard to understand the effects of things like arning drop, lowered ride height, wheel offset, tire size, drop spindle, etc.

This way, it can help me decide the modifications and parts that I buy.

I'll post my numbers at some point too.

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#6 · (Edited)
195-75R14
10 1/8” to cl of cam bolt
9 1/2” to lower ball joint at movement point of ball
8 7/8” front ride height at pinch

Arning drop
All new hardware, bushings, Moog ball joints at refresh 1500 miles ago
SOT Opentracker alignment specs
Drake 620# lowering springs
QA1 stock mount shocks

Tracks well, don’t feel a push or loose but haven’t driven it to the limits. Minimal roll, firm ride likely too firm for most street cruisers but I like it to feel more like my race cars.
 
#8 ·
195-75R14
10 1/8” to cl of cam bolt
9 1/2” to lower ball joint at movement point of ball
8 7/8” front ride height at pinch

Arning drop
All new hardware, bushings, Moog ball joints at refresh 1500 miles ago
SOT alignment specs
Drake 620# lowering springs
QA1 stock mount shocks

Tracks well, don’t feel a push or loose but haven’t driven it to the limits. Minimal roll, firm ride likely too firm for most street cruisers but I like it to feel more like my race cars.
Thank you! I appreciate the extra details on the ride quality and components. Very helpful.

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#7 ·
215-70R14
Center of eccentric is 8 7/8”
Center of ball joint boot is 9 1/2”
End of pinch weld (masking tape) 7 3/4

These are as accurate as I could get with a tape...I could not find my square.


I have done the Arning drop and pretty much stock 390 w/AC. I am pretty sure the springs are original (replacing is on my to do list). Most other items are new repop for stock spec

745215

745217
 
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#11 ·
The Knapps has a good looking ride. The stance on mine still rakes slightly to the rear depending on how I look at it. I did a full refurb of the suspension front and rear. The rear got the companion QA1 shocks with Grab-A-Trac 5 leaf mid eye rears. I wanted 4 1/2s but they were backordered for a couple of months. In hindsight I should have got top eye for the stance. While the rake is better it’s not quite what I was looking for. Drives great though, it’s a looks thing. I wanted a bit of the modern rake but still want a 52 year old car look and feel.





 
#12 ·
The Knapps has a good looking ride. The stance on mine still rakes slightly to the rear depending on how I look at it. I did a full refurb of the suspension front and rear. The rear got the companion QA1 shocks with Grab-A-Trac 5 leaf mid eye rears. I wanted 4 1/2s but they were backordered for a couple of months. In hindsight I should have got top eye for the stance. While the rake is better it’s not quite what I was looking for. Drives great though, it’s a looks thing. I wanted a bit of the modern rake but still want a 52 year old car look and feel.





Thanks for passing the photos. You both have really nice looking rides. Can't wait till I get my 67 on the road.

I plug in your numbers in the next couple days and post some of the results. This will be a nice comparison of two cars with similar setups, both have arning drop, similar tires, with the main difference being ride height, which changes the suspension geometry and directly changes the roll center height.

Hopefully sometime without the arning drop will also post their numbers. Then we'll have nice comparison going.

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#14 ·
Thanks guys...I am ashamed how dirty it is. I will say my front end is lower than it should be with springs that are tired and stock 390 with iron everything.

Your car looks great, Vegas. I love the vintage colors.
 
#16 ·
Thanks. The Lime Gold that One Day Paint and Body used on the last collision shop work in the 90s wasn’t quite a match but still captured the essence. Dad says that through the 90s and early 2000s these were more or less old cars. Neat old cars but not quite the popularity as classics now and period correct restoration parts were not plentiful. You can see the difference in the proper PPG code on the tail end of the rear quarter. I had a knucklehead hit the car while parked and did the spot repair myself instead of paying the deductible.
 
#22 ·
Thanks @Knapper and @vegasloki ! Do you guys mind if I post your roll center and camber gain results on this thread? Won't be until tonight or tomorrow morning but I put all the numbers in this morning, the only number I needed was your camber setting, which you guys just provided, so we are good to go.

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#24 ·
Thanks @Knapper and @vegasloki ! Do you guys mind if I post your roll center and camber gain results on this thread?
Fine by me. This is way beyond my level of understanding at this time. I did my own alignment with the Longacre bubble tool. I do want to bring it to a shop to see how close I came.
 
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#26 ·
While maybe not relevant I thought I'd share my experience on my 66. I don't do automotive work for a living nor race. I'm a electrician by trade, been to trade school as well as some electronics schooling which means I have some understanding on how angles work and there's more then meets the eye. So when I really became serious about making my Mustang handle well on the street it had to ride pretty much like street car and not a unloaded dump truck. I bought a good suspension book more geared for stock car racing along with asking a lot of questions here. I understand what you're doing but everything is going to be a compromise in the end. At least on the 65/66 the upper control arms are going to be mounted higher then the upper balljoint. Right away you know this is bad on several counts. Roll center below the road surface and positive camber gain. With the stock upper arm, it needs to be lowered by 1.75" to get negative camber gain. You can't lower the stock arm that much because the angle of how the ball joint is mounted will break the balljoint. The most you can do is 1" and that's right at the limit. A aluminum wedge kit was sold to correct the balljoint angle but it was expensive for that it was, like $250. It blocked off the grease fitting and bent the bolts holding it all together. You still had a flexing arm. The next problem with the arm is that they are designed to be used on either side which means zero caster built into them. These cars were designed for maybe 2° + caster. It can get tough getting more caster. To be it seemed the best solution was a purpose built, aka, aftermarket control arm. This could fix all issues at once.

As you lower the control arm, you increase the distance between the 2 mounting points for the spring which lowers the front. On the 65-66 the 1" drop will lower the front by about 5/8". Going to 1.75", I never bothered to figure it out but fair to say more then 5/8". Let's say 1" for argument sake.

Since the Mustang suspension is rear steer it means on extension of the suspension the tires will toe in and toe out on compression. They also have a lot of travel! That means a big change between toe in and toe out. Once you lower the car by what ever means you now have a much greater range of toe in and less range of toe out compared to a completely stock suspension. This comes back to bite many people. You will read guys saying after going over something like a rail road tracks the front end is going to stay up in the air with the front tires squealing until they hit the brakes to settle the car back down. The excessive toe in binds the suspension.

So you start to make compromises on all these things to make them all work as best as possible together.

So what did I do? I started to look for a control arm with a altered ball joint angle, added caster and could be rebuilt with readily available off the shelf items, no proprietary items. It also had to be shorter to help negative camber gain. While I was free to lower the arm more then 1" I stayed at 1" to minimize other unforseen effects. For me the best fit for my needs were Street or Track. Their control arms use rod ends that can be adjusted for increased caster. As shipped, they're set for 3° +. At the time I don't believe there was another brand that offered the feature for caster. I ultimately went for their strut rods with rod ends that are adjustable again for caster. Followed up with their lower arms that use a mono bearing instead of a bushing.

I run 4° + caster, 1.125° negative camber and 1/16" toe in. Tires are 215/60/15. With steel bearings the ride is actually quite compliant. They remove a lot of binding of the rubber bushings. So much so springs that were firm on a stock suspension become too soft. I actually had to move up to Scott Drake. .620", 600#. With stock GT spec coils I would be on my bump stops sitting still with just a second person in the car. The ride is firm but not at all harsh or uncomfortable. I would say similar to a modern Mustang.
 
#27 ·
@7T02S feel free to post the calcs with those specs. Unless a suspension is engineered for the app like SoT or OT you’re going to be pretty constrained on what you could do with stock geometry and parts. I didn’t mention in the previous posts I’m using roller perches.
 
#28 ·
These cars respond really well with a few simple tweaks. Just lowering the upper arm 1" makes a dramatic difference. I don't believe it puts it into a true negative curve but helps a lot. It also gets the roll center above the road surface. Add a 1" front bar, good quality shock and some caster with a little bit of negative camber. I'd suggest adjustable struts as one of the first non stock suspension component. Getting rid of the rubber bushings does wonders for stability and better feeling. The car will stop much straighter. I'm a fan of the roller spring perches.

As @vegasloki said Opentracker Racing or Street or Track are two excellent, well respected vendors.
 
#29 ·
Thanks Huskinhano, good advice. One thing though, from everything I've read and from what I've seen in the calculator, is that the mustang's roll center never goes below the ground (at least for the 67 geometry), whether it's with or without the Arning drop, original or extreme lowered ride height, tire diameter, etc. I can get it very nearly on the ground if using the following: without arning drop, small diameter tires, and an extreme drop but I don't think that's a likely combination and it would probably need high static negative camber. I looks like the stock geometry might give around a 2.25" roll center height and then typical mods raise it to around 4.5" to 6.0". Don't quote me on that though, just some observations from the calculator.

Regardless, it's more about how the car feels to the driver than anything else. You're right though, most of the common modifications on this suspension raise the roll center and thus will make the car roll less by getting it closer to the CG, but most importantly, help the camber gain curves which help the inside and outside tires maintain grip while cornering. I think a lower roll center might work well if the camber gain curves could work out and springs, shocks, and sway bars were adjusted accordingly (stiffer as the roll center goes further from the CG); but the only way to do that would be to do some major modifications to most of the pivot locations. I talked with Mike Maier sometime back and he said that a roll center very close to the ground seems to work very well on the track as it helps the forces on the tire's contact patch. I've read that elsewhere too. It's just really hard to do that without non-typical modifications like changing all the pivot locations at the chassis and spindle (x and y) and arm lengths. It would also probably need three degrees static negative camber to work to keep from going positive, since the camber gain curves aren't as good from what I can see. I'm not an expert on this by any means, learning as I read more and play with more settings in the calculator. It all doesn't mean much unless I were to actually try it for myself on the track...
 
#33 ·
I spent some time digesting the information from the links @stephen_wilson posted with drawings of the 65 suspension. Thanks again Stephen!

The thing that threw me was the 65 spindle drawing had a ball joint axis angle of 6.3 degrees. That just didn't jive with my early 67 spindles. I went to my shop and measured the angle and it comes out to around 7.7 degrees on both spindles, which is the average of what is show in the pictures with the bar pushed down and then up to cancel it the two diameters.

I had read that this wasn't one of the differences between 65-66 and later spindles. What it does is it pushes the upper ball joint outward or the lower inward by 1/4 inch. Assuming the lower stays at the same spot, that gives 1/4" more wheel clearance at the top.

Either they are different, or the drawing of the 65 spindle is wrong. Regardless, I'll stay with the dimensions I measured in my spindles.


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