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Correction on Shelby Drop

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304-dude View Drop Down
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    Posted: Aug/09/2019 at 9:58am
I will be updating my thread to remove all info on Shelby Drop, and my recent vector charts. Will update with correct and more details to go with the update.

Found that the app i used rounded integer values, and compounded the issue when making muliple changes. To put it simply stock upper control arm setup location is fine. I ended up chasing my tail on erroneous values.

Just had to simplify to get a correct assessment.

To show here is what the stock location does for upper arm travel. You want to see a near 90° angle for rest and full travel within operatinal ranges.

I should have just done the upper angle chart earlier, but did not expect to compare location points, until asked with stock components.

My thread will explain the details, since this topic is for addressing a needed correction, in a direct manner, not to go into the subject of suspension geometery, unless some one wants to address it in my thread.

On the left, center is at near stock location.

The blue near vertical line is stock about 10" between arm pivots on the body.

71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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tomj View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Aug/09/2019 at 9:33pm
i did the so-called Shelby drop on my '61 American, using a RideTech Mustang part. alas, it involves making a complete upper arm system, which on this car, is a good thing because the upper trunnion system is a design disaster.

WHOLLY KARAP does this improve handling of this car.


then i managed to get 2 degrees negative camber and it was HOLEY CARUMBA again -- huge improvement.

1961 roadster american, 195.6 OHV, T5
1968 american, 199ci, T96
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304-dude View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Aug/10/2019 at 4:39am
Originally posted by tomj tomj wrote:

i did the so-called Shelby drop on my '61 American, using a RideTech Mustang part. alas, it involves making a complete upper arm system, which on this car, is a good thing because the upper trunnion system is a design disaster.

WHOLLY KARAP does this improve handling of this car.


then i managed to get 2 degrees negative camber and it was HOLEY CARUMBA again -- huge improvement.



My statement is about 70 on up AMC suspension. Though, changing from trunion will require some relocation adjustments. There is a kit offered by a member for changing out trunion for 70s style suspenion, which should function like your setup.

The Shelby drop basically adjusts ride height and incorporates anti dive (which AMC utilises).

To simplify, for 70 on up suspensions... the only way to obtain camber control and tighter turn stability is to change arm angles. The Shelby Drop is limited by lower control arm length and lack of ease to move far enough to drop. AMC suspension hump design does not make an easy option for relocation, unless you weld a mounting bracket at the top of the frame and make cutouts for clearances for the bushing ends.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMXFSTBK390 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/10/2019 at 12:19pm
The credit for revising the 1965-70 Mustang front suspension should go to the Ford suspension engineer Klaus Arning, who also designed the suspension for the AC Cobra 427 and GT40. Carroll Shelby applied Arning's relocation of the upper control arms to the 1965 Shelby 350's. I have owned four daily driver Mustangs (65 coupe, 66-67-68 fastbacks). The only problems with relocating the upper control arm was tire-to-fender clearance and the alignment shop won't have alignment specs for an AMC with  relocated control arms. The relocation of the control arm was to drill new holes 1" lower and 1/8" rearward. These new holes will run parallel to the centerline of the original holes Then, reassemble front suspension in reverse order. You will then see the old holes directly above the upper control arms. Very clever, not that difficult, and didn't cost anything to do!  I can't imagine trying to do this to my 1968 AMX because it doesn't allow for this modification unless major welding & fabrication is performed. There are much better alternatives.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Aug/10/2019 at 11:51pm
304-dude, yeah, i know your work is on the newer chassis. 

the old Nash trunnions were awful. the transitional trunnion installs (starting 62? 63? in 10/80 chassis, and 68-type rambler/amx) are at least very reliable, if not amenable to hacking. so reliable in fact i feel zero need to replace them with another system. of course this means you'd have to accept it's geometry more or less as-is. and 'shelby' mod very difficult due to the pocket pivots.

in a 63, 64 Classic or Ambo, assuming you want stock geometry, i PREFER the upper trunnion system. it's drop-dead reliable, and 300,000 mile life. i did drive one that long. ball joints (lower) needed replacing, trunnions needed cleaning and greasing.

of course no one would really want to autocross a '63 classic. but it rides great!

if you did "shelby drop" on any car, and changed no other components (whether thats possible depends on the chassis, etc), for a given upper arm length, lowering the pivot generally pulls the top joint (trunnion, ball) inward, increasing camber negative, pulling tire away from fender. unless you compensate for it with a longer upper arm. the amount of static displacement is very small however, the point of the 'drop' is dynamic/

yeah, the Nash based car suspension, as terrible as it is in many ways, is a a hacker's delight, since it bolts onto the chassis, and isn't based on welded in pockets in the unibody.

amxfstbk390 -- typical, and sad. the famous guy gets the cred for others' work. might not be Shelby's doing, but who knows. thanks for the info!




Edited by tomj - Aug/10/2019 at 11:59pm
1961 roadster american, 195.6 OHV, T5
1968 american, 199ci, T96
sr-ix.com

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343sharpstick View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 343sharpstick Quote  Post ReplyReply Direct Link To This Post Posted: Aug/13/2019 at 12:21pm
I just want to add a quick note here, not applicable with the trunnion cars. Just want to note that a few manufacturers build upper ball-joints with a longer shaft (Howe racing and QA-1 for example). This will have basically the same result as moving the mount-point of the inside of the upper control arm.

When I designed my coil-over setup I went through the geometry using the 70 and later steering knuckle, and a longer upper ball joint to get a more ideal angle to the upper control arm.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Aug/13/2019 at 12:37pm
Originally posted by 343sharpstick 343sharpstick wrote:

I just want to add a quick note here, not applicable with the trunnion cars. Just want to note that a few manufacturers build upper ball-joints with a longer shaft (Howe racing and QA-1 for example). This will have basically the same result as moving the mount-point of the inside of the upper control arm.

When I designed my coil-over setup I went through the geometry using the 70 and later steering knuckle, and a longer upper ball joint to get a more ideal angle to the upper control arm.



Hi, understood about some ball joints with dropping... but i did make a vector map of stock oem comparison to dropping spring saddle.

You may look into that as another option to add to your existing platform of upgrades. I figured you were aware of the dropped perch / saddle mod, which i have incorporated in my build. I tried to make the readers aware not all mods are strictly for my non stock application.

From what i see with one inch drop, you still have some negative camber on the upper swing. Mostly by the upper arm pull, which the lower arm cannot compensate for on its travel.

Here is the vectors on the suspension travel comparison thread.

http://theamcforum.com/forum/oem-vs-dropped-spring-saddle_topic101395.html

Edited by 304-dude - Aug/14/2019 at 5:58am
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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