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OEM vs Dropped Spring Saddle

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304-dude View Drop Down
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    Posted: Aug/13/2019 at 8:37am
This is a ballpark vector drawing of OEM vs 2" drop spring saddle.



Farna asked for some details in comparison, which until now, is the best I was able to do with what data I have. So being ballpark, they are close enough to get a fair assessment.

Below may be hard to read, so I will explain each section of importance.

First thing, the purple line represents the spring saddle. It is the only thing being changed in the setup, outside of the UCA and the rest of the suspension is now pulled up almost 2.50". Since the saddle is up further on the arm, the drop is multiplied by the distance ratio at the arms pivot at the body. Its not a large gain, but it does give around 50% more drop than just by the difference between tall and short saddles.

Second, notice the black vector lines represent stock, and the bottom line (LCA) does not stay in the positive angle range. Thus will always increase negative camber when suspension is under hard cornering and going over bumps.

The red (at top range of compression arc) and blue (at rest) vectors, are with a short 1 inch tall saddle. Notice that total arc is limited within a 2.4" range. Going outside may hit bump stop or frame rail if not used.

Outside of loosing a wee over .600" (Donohue recommendation of 3" travel), to get near zero camber gain in suspension travel, you'll get better control over using dropped spindle plates, making this mod well worth it.



Edited by 304-dude - Aug/16/2019 at 7:50pm
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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mbwicz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mbwicz Quote  Post ReplyReply Direct Link To This Post Posted: Aug/13/2019 at 11:00am
Just to confirm a couple of things - this is for a 70 and later application (upper ball joint), and this would be a custom fabbed spring mount? You're just trying to show the difference in camber gain between a lowering plate and new spring mount? Does anyone offer a custom spring mount?

Mike
1970 AMX. Needs everything except patch panels... (that's what I thought until I blasted the quarters!)
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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/13/2019 at 11:44am
Yep, 70 and later suspensions.

Nobody makes the kit, but there are three options.

One use early 70s Mustang/Torino saddles. You can also obtain Mustang springs with similar to OEM spring height and load capacity. Which will cost a lot more than just the saddles. On the plus side you can use poly bushings for Mustangs, as Mazda 323 rear strut bushings are no longer being produced. You will need to burn out the rubber to pull the mounting pin from both AMC and Ford saddles to swap with the poly bushing install.

Or to keep stock or AMC springs... you can modify the AMC saddles by cutting them down as in sectioning and having them welded, or modify the Ford saddles for AMC springs. By cutting and welding the spring location pads at proper spacing to the Ford saddles.

So, basically 3 options, and maybe one of our fab guys will see this and make them for the masses. It would help improve at the track or at auto cross activities.

For second part of your question... yes i am comparing two options stock and dropped saddle. Black vectors for arm location angles are OEM stock suspension.

Off and on, I have mentioned this option, but most have rather do simple bolt on plates. I got the idea from way back around 2000 or so, by a website i stumbled upon. It was an easy recall, when I started my build. So i opted to buy a new set of Ford saddles and swap spring holder ends.

I thought, when reading through my thread, and by my few attempts at explaining how the spring drop does better, it would be obvious as to removing camber gain... So after getting my vectors down for completing my suspension build, and having farna ask about what this would do to stock on the vectors, i made another attempt with stock compontents.

My setup is nowhere like stock any more, with locations and measurements, so the two are apples and oranges.

One easy way to detect how much camber will be effected is to look at the vertical lines between low and high positions of the arms. The narrower of the lines, the more controlled the camber along the arm swing. Another thing is watch the upper arm and compare it to the lower arm, when suspension is deep into compression, but not at its extremes. Untouched stock will have lower arm pushing at max length, while upper arm will be at the start of its pull away and becoming shorter. So once the turn becomes very deep, the upper arm will be pulling in and adding negative camber, while the lower arm has not enough swing to compensate, thus a top end camber change to mess with proper grip.

Any camber change in going into mid turn to near exit will change friction pad on tire. Once the coeficiant of friction has been surpassed, slip will happen, causing no recovery until momentum has disipated enough to grab traction.
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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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: Yesterday at 7:46am
I waited a bit, plugged in more accurate data, and compared any changes. Now that I have gone through a various results, I can see the 10.50" gap between upper and lower arms at the ball joint ends, can be lowered for slightly more drop.

Though it depends on how much gain is needed to warrant shortening the distance. But that is if the measurement of 10.50" happens to be what is OEM. I assume 10.25" would be closer to guessing, but i figured to use the high value, which wont effect much, as a .250" variance will slightly raise the lower arm, and slightly drop the suspension.

To me it is only required when matching lower arm travel to be inline with the upper arm swing. My calculated sweet spots are built around having both arms swings follow along the same path as much as possible for the drop being applied.

Thus the vector lines having a mirrored look of angles of the arms. Because of differences in arm lengths there will be a ratio of angle gain between lower arm and upper arm. Like 5° for lower, and 8° for upper, for example. Unless one changes the arm length of a given arm, that ratio will stand for any other change within the suspension.

There is a limit, to how much drop one can achieve to still be affective at turning and handling. Too much drop will invert the arms swing travel, causing improper handling in a turn.

On the plus side, if one is willing, can move the arm end distances within a close match (sweet spot), where both arms follow up swing down swing paths, by use of a not so short spring perch to equalize arm rotation paths. To compensate, one can use a short spindle drop plate to counter the drop loss or add further drop, while dialing in the proper geometery to kill camber gain.

All in all its a balance to get the upper arm to go no higher than 8.5° at up swing, while keeping lower arm to limit below 6°, due to upper arm angle ratio, or to keep from hitting the bump stop or bare frame (no bump stop), to make bottom swing a mirror that of upper swing path.

Dialing in a stock supension can be done very well with slightly modified OEM components, since one can use both custom drop plates and shortened spring perches together. Though the drop plate would be setup last, as any existing set drop may not alow for tire clearance on upward swing, or bottom out on light bumps.

Note... on a spring perch drop, for every inch dropped, you will loose an inch from rest to full travel on up swing.

Example, my custom drop will only have about 2.75" usable travel from resting position, because my 2.5" suspension drop on a short perch, has removed head room of the suspension travel. If one combines a drop plate, which cannot be done on single piece Mustang II spindles, but can be done on 3 piece units, the outcome could be a real frame dragger if wanting to slam an AMC on the cheap.



Edited by 304-dude - Yesterday at 1:00pm
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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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: 5 hours 51 minutes ago at 12:46pm
I found a direct fit front shock for the lowered spring perch, as it sets the mounting about 2" shorter than stock. Look at front shocks for 1999 Jimmy, S-10, Blazer... etc.

The good thing is that there are many available options over the counter and through suppliers.

These shocks will have about 3.5" max of travel, compared to 5" oem.

Again, the perch drop will loose almost half of stock travel. Though you may have a total of 3.5" travel under free swing, if track setup allows it.

Since I had planned on modding my spring saddle to fit eye style mounting, this shock may work for my perposes before I decide on the mounting bracket fabrication, and may give me a cost effective option to test with, until I am ready to spend a grand on a set of rebuildable performance shocks.
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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mbwicz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mbwicz Quote  Post ReplyReply Direct Link To This Post Posted: 5 hours 42 minutes ago at 12:55pm
What is the shock ‘leverage’ on this suspension?  I’m assuming that 3.5” is shock travel, not wheel travel. 

Some really in-depth work, nice job. 

This is interesting to me, because I’m going to make a driver out of my AMX, and want to have 15” wheels. I’m worried that lowering plates with 2 or 2-1/2” won’t work with the old school wheels. 

Mike
1970 AMX. Needs everything except patch panels... (that's what I thought until I blasted the quarters!)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: 4 hours 57 minutes ago at 1:40pm
Originally posted by mbwicz mbwicz wrote:

What is the shock ‘leverage’ on this suspension?  I’m assuming that 3.5” is shock travel, not wheel travel. 

Some really in-depth work, nice job. 

This is interesting to me, because I’m going to make a driver out of my AMX, and want to have 15” wheels. I’m worried that lowering plates with 2 or 2-1/2” won’t work with the old school wheels. 

Mike



Ok, understood... I am recalling to an old website that was dedicated to a guys suspension mod using 73 Mustang springs and sadles, on a stock Javelin. Cant remember his intended use was, but 15" rims were part of the build.

I assume there will be some kick out with lower arm, but the camber adjustment will be set more to the inner part of the frame for compensation, when realigning and suck the wheel back in. So most likely the rim and tire should be fine with clearance with wheel trim lip.

I suggest setting caster to max adjustment out, if that is not done already. Its not required, but it does make some difference.

So, its a given that this mod will work, when lowering plate won't allow tire clearance.

As for travel, it is lower arm, which will extend even further to the wheel tread... guessing another .75" travel, which may not be that far off from being all that noticable from stock.

Shock leverage is at stock mounting points, the shocks them selves are just shy of being 2" shorter than OEM. The S-10 weight is close to Javelin, but with OEM Chevy shock, it should be soft enough for a lighter
body.

The guy did mention no issues with driving it in the streets, but who knows how smooth his streets are.

Mark Donohue mentioned in the book, Unfair Advantage, that his 71 Javelin car was set with 3" travel. So, the tires being further out from knuckles, the added distance will also add to the amount of wheel travel.

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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