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lowering front of a spirit

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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: May/31/2019 at 9:28pm
handling in turns is substantially affected by the rest position of the upper and lower control arms. on the few, earlier cars that i've put tpe measure to, at least, correct geometry is when the centerline of the lower outer balljoint/trunnion is at the exact same height as the inner arm pivot.

with unequal-length A-arm suspensions, camber varies in turns, a lot. chopped springs make the car squat, like it's in a turn, and will make it feel heavy and bad.

there's this idea that lowering the center of gravity improves handling, for fairly intuitively obvious reasons. but the net improvement isn't all that much, and building in bad geometry will do fgar more harm than the lowering will.

if it's just for looks, or for straight-line drag racing, it probably doesn't matter much.

1961 roadster american, 195.6 OHV, T5
1968 american, 199ci, T96
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billd View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: May/31/2019 at 10:18pm
Tom hit on my question in all of this. Normally these are engineered so the upper and lower arms are in a line straight out from the pivot point.
Since it's SLA, ideally you want them to swing so that they are in the point of their arc where inward and outward movement of the "ball joint" is minimized.
The further up the arms are when at rest, the more drastic the movement inward and outward as they swing up and down. Straight out the in/out movement is minimal.
The more they deviate from straight out at rest, the more drastic the camber change is. 
Further, and this is from current experience with my Eagle - the springs I ordered a few years back are TOO STIFF and make the car sit a bit high - it cannot be properly aligned. Eccentrics are maxed out. Can't get camber in specs and the car isn't THAT far off of stock, no more than an inch. 
Another issue when using standard parts, bushings, etc. - is that when you lower a car, the upper arm is up from level and so the spring support, to which the shocks bolt, is swung up and in - making the top of the shock angled inward.
If the car is made to sit higher, like mine does, the upper arm is swung down, forcing the top of the shock outward - and it's impossible to get the shock tower on without holding hard against the shock to force it inward. 
So using spring length or "stiffness" to change ride height causes camber to be hard if not impossible to get into specs and causes the tops of the wheels to move in far more drastically as the car's height changes due to bumps, turns, etc.
And - it causes the shocks to tip hard in or hard out at the top if using stock bushings in the spring support because the upper arm is no longer out straight from the car but is angled up or down - thus the shock is angled in or out.

So - how do people deal with the impossibility of alignment, drastic swings in camber on bumps and turns, and the shock position issue?

for examples - put a jack under the cross member, raise the car with the top off the shock tower and watch the shock top end move outward. If you could lower the car from curb height, you'd note the shock tip in hard.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote amcfool1 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/01/2019 at 7:02am
hi, billd, when I was rebuilding my 84 sedan a year or so ago, I did the same thing. Put in new front coils. I wasn't trying for a lift, but apparently, these were the only springs that ESPO had, so I bought them, listed for an Eagle, though I believe they are the Javelin springs.
Anyway, put them in, car sat nose high, a LOT! So, I got a set of new Extra HD Eagle rear leafs from Stengel Bros. in PA,, which they arched a 1/2" over stock, and installed them. car sits level, and looks good, about 1" higher than stock. The ride is a bit harsher, though not enough to bother me.
The front end was completely apart, so off to the alignment shop. They did not tell me there were any problems, and the car tracks straight. New shocks all around, NAPA brand.
One problem I noticed just a week or so ago, is that the poly bushings in the spring seat are getting squeezed out. (rebuilt spring seat from Arizona AMC). Don't know if this is a result of the (unintended) lift.
Also, the car does not like steering at full lock, don't know the issue there, related?
Otherwise , is a great car to drive, has Freakride subframe connectors, and feels as solid as a rock on the road.

So, back to the Spirit, new rear leafs?
Option #4. though the most expensive!
We'll take it one day/dollar at a time.
thanks for your input,  gz
george z
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jun/01/2019 at 7:33am
amcfool1, as for poly bushings in the spring seat being squeezed out... donno if the later year cars used a different diameter or what, but the only poly bushing that fits proper is from a Mazda 323 rear end link replacement, which is no longer being made, and are impossible to find online.

Mine are dry fit into the seat tube and when everything is in place the bushings sets pretty well secure. Though, from the original thread on another forum, stated that the concerns were from bushings not staying in place. The poster of the bushing thread, replied back saying that the bushing has no place to go, as the bushing cannot go any further than the gap between spring seat and UCA.

Haven't been on the road, but had many test installs with high rate spring compression with 70 HD Hornet springs, and had to work at breaking free the solid fit after settling in. The disassembly was required for a late customization that required welding the bushing tube and seat. Else i would not know any better on how much the poly would stick in place after settling in.

From my experience, do not lube to fit in the tube, and allow for a few days to have the bushings to settle with the springs compressed if leaving the car raised.

71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Jun/02/2019 at 1:39am
billd did a better job than i ever could of describing the on-going complexity of mostly camber, but also toe, bump steer, shock, ride, etc relative to stock or "correct" springs.

i've also personally done a lot of stupid things to my cars, and was actually happy with setups that were... subpar is a nice way to put it. there's a lot of redundancy in there! many of the dumb things were done to my '63 classic wagon. i replaced all four coil springs with custom wound new ones from a then-local shop. 1" taller ride height and stiffer (forgot how much). i was quite happy with it. tall 15" pickup truck tires. that car did everything i wanted but handling, umm no. rode OK though. 9" grtound clearance!

but if you want to actually *improve* handling, like turning the steering wheel under power, it's actual effort. i learned the hard way that the place to start is with stock stuff in the exactly correct configuration, determine precisely wtf it is that is lacking, and change one thing at a time to measure the result.

(i used to scoff at factory tuning (spark fuel gears axle tires) and now know, damn, AMC did a good job! the compromises are about as good as you can get at what's there. of course real power increase allows for changes, etc. same with handling and drivability and especially longevity: stock suspension is good at what it's designed for).

i did some actual research and reading on suspensions for my current car (hardly bragging, for the first time in 40+ years of messing up cars). turns out very little change made a large improvement -- Shelby drop, so-called, for the same reason the Mustang needed it. while i've made a number of radical-seeming changes to the parts themselves (basically fabricating unavailable stuff) the geometry up front is 100% factory stock settings, *except* Shelby drop 1". and the new metal allowed me to get 1/2 degree caster and -2 degrees camber. same geometry.


at the above  page are links to a 2-D suspension simulator, with stock setup and my 1" shelby drop setup. you can drag the roll angle thingie and induce roll, and see how much the roll center changes, and in the WRONG DIRECTION! stock. AMC wanted grannie to go slow in turns by making the car feel like it would roll over! with the *sole change* of the 1" shelby drop, the roll center moves in the opposite direction, vastly improving where the mass grips the road. i can tell you that my car stays flat in turns and i have no roll bars and dont need them. (springs are stiff and air springs are inherently progressive).

i also learned, the hard way, and i admit by accident, how much of this car's understeer is built into the *rear leaf spring setup*. two things determine it: the height off the ground of front vs. rear spring eyes, and the canting of the springs inward at the front of the car, which had not once in my life noticed; eg. looking down at the car with x-ray vision, bird's eye view, the springs are not parallel, they point inward at front (in this chassis, far more than say a 72 hornet). it took me some time to visualize how this created understeer but it does -- and a lot of it.

the short of it is, when the car rolls on it's springs in a turn, the  inside wheel moves back a bit and the outside wheel moves forward a bit. small fraction of an inch translates into noticable counter steering. i discovered this by accident when i moved to a rigid wishbone system with a 7.5" mustang axle.

funny, the torque tube cars don't have this oversteer since no leaf springs. that's the geometry i copied because i knew how it worked in the bigger ramblers, because i went to all air springs for many reasons.

there's so much more design subtlety here i simply never imagined -- or bothered to look at.

1961 roadster american, 195.6 OHV, T5
1968 american, 199ci, T96
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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: Jun/02/2019 at 1:55am
oh one really nice thing about air springs...

i kept it stupid-simple. each spring has a couple feet of rigid plastic tubing that runs to a Schrader valve on each fender. i carry a nice double-action bicycle pump and tape measure in the car.

the first time through i set each spring air pressure so that for that corner, two fronts, two rears, the static loaded height was correct: the front lower arm pivots the exact same height off the ground; out back, the spring exactly 5" tall (half inch over half way through it's travel). then i made marks on the fender, the lower edge of ther styling "spear". (actualy i used a paint pen and wrote the height in inches).

now when i head off on a drive -- tomorrow AM, a bunch of us (pre-76 mostly sports cars) are out on a rally/tour (600 miles in 2 days, mountain and desert roads), today i measured each corner's mark, and tweaked ride height to the correct height, spot on. (the hoses and/or Shraders leak a tiny bit, like 1 PSI/month).

it's cheap (RAMBLER MENTALITY) but also light as possible. and compressor setups assume all air springs are the same, mine aren't. each corner is different! driver side front takes more air pressure for the same height (something like 37 left/32 right) due to uneven weight distribution.

1961 roadster american, 195.6 OHV, T5
1968 american, 199ci, T96
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jun/02/2019 at 9:18am
A bit over a year ago my neighbor, a street rod guy, Iowa rep for Goodguys, "Barn Finds" cars and parts, runs at salt flats, etc. - anyway, he came to me asking me to keep my eyes open for "10" front brakes from an AMC". He wanted spindles, backing plates, drums, the whole thing. At that time I had considered putting disks on the front of my 73. Hmmmm, this may force me to make jump to disks.
I told him I'd put the car in my shop, have it on stands with the wheels off and if he came and took the parts off he could have them. 
A couple months later he called me and said I should come over to his shop, he had something to show me.....
My 10" AMC drum brakes were on the front of his 49 Ford.
Why am I mentioning this? Because it ties in with ride height, geometry, and more. 
He had the spindle mount area machined down a bit (like I did with the spindles I used for the Kelsey Hayes brakes I put on my 73 - I machined the backs of the spindles to move them in to center the rotors in the calipers.
He then had plates made to mount the spindles on his steering knuckles (think I have the nomenclature right for his car)
He calculated the drop he needed, how far in or out the spindles needed to be from the king pins for his wheel offset to keep SAI and other angles correct. 
So I guess what I'm saying is that dropping a car using plates is a far better way because you can compensate for the changes with the plate size or thickness, wheel offset and so on.
In short, you can make things line up again and keep those control arms out STRAIGHT from the car, making it simple to align and keeping camber where it's needed - and not cause drastic camber jumps with each bump or turn. 
Straight out, the ends of the arms move very little inward as they swing up and down. 
Cut a spring and now the arms are already started their inward swing in that arc they must travel and since the upper arm is shorter (SLA - Short-Long-Arm suspension) it's going to move in a lot farther faster - it swings a much tighter arc than the lower arm which doesn't move in as much as it swings up or down (from straight out, like factory, both arms swing IN as they move up OR down, but the upper arm swings in farther faster)
Using springs you make the camber off to start with, and lead to very drastic changes in camber with each bump or corner. Using plates, you can compensate with plate thickness, wheel offset, spacers, whatever, even wheel SIZE.

But again - what do folks do about the shock being tipped in hard when lowering a car by cutting springs? Poly bushings? If you install the stock rubber bushings correctly, meaning spring support level when control arm is at curb height or straight out, then when you cut a spring, you move the control arm UP, tipping the top of the shock hard inward - meaning the shock is always got terrific side-force on it, wearing the sides of the piston, premature shock failure and the inability to keep the shock top centered in the spring tower top. 
Wondering what people do about that?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jun/02/2019 at 9:43am
Agreed on dropping by spindle rather by springs. Things get complicated with limited adjustments with stock suspensions. Though if one must cut springs the 1/2" off a coil is a compromise that may work without making too much for complications that can be addressed... as in a photo of the recent aquisition of the racing Spirit thread, it shows the shock tower shimmed to allow the shock to have enough travel from being lowered by the spring height change.

I admit, once I started with what was considered a basic custom rack install became a bit of a full suspension upgrade and redo. Once I found one issue, it led me to another to correct. Some of the issues were limitations with factory components, that were never intended to be used in heavy race or out of spec adjustments.

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 Doug in New Freedom Quote  Post ReplyReply Direct Link To This Post Posted: Jun/02/2019 at 9:46am
Not suggesting you do this but, back in the '70's when I Auto Crossed my Gremlin X I took Muffler Clamps and installed them on the top of the two front coil springs to compress the front springs and lowered the front. Drove it that way for years. Also put traction Bars on the rear springs to stop Wheel Hop in hard braking.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jun/02/2019 at 11:55am
LOL - everyone is walking all around my points and questions save for tomj
Clamping coils is not different than cutting them in my questions/concerns. It STILL changes drastically the camber changes when driving, and still tips the top of the shock to the inside hard. 
My 73 had broken front springs - the effect was lowing the car. Guess what - it snapped one shock off and the other was totally worn out - the piston had a quarter worn off one side and it was no longer functioning. The springs were broken in a way that was the same effect as cutting half a coil off. Camber was bad, tires were worn just the same as if the camber and toe were both off (which of course they were - DUH - car was lowered)

The issue with my 68 was wheel hop on acceleration - autocross was fine as far as braking and steering/cornering. A couple of guys broke things trying to catch me. That car was LIGHT.
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