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A friend had a date with a ditch once, chipped one of the teeth on the steering rack.

My initial thought would be something going on in the rear, something loose, failing, compliance while driving. Definitely get it off the ground and start pulling/pushing

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Peace, Ron

my front uprights are merkur scorpio, i was wondering if the ackaman was correct given that the scorpio has a longer wheelbase so the convergent point of it's steering arms is behind the rear axle.
many years ago i worked for london transport, the rm bus used independant front suspension, LT in their increasing demand for a bigger bus added a section to the middle increasing the wheelbase by about 3', the effect of this was that it would "drag" the inner rear wheel over the curb on turns due to incorrect ackerman.
my car is the opposite.
some years ago i worked on a 69 camaro race car that was wearing tires at the front and the driver, one Jacky Oliver complained that he could not get the back round, this was due to the need in europe to use goodyear slicks and now it was on hoosier here at sebring and required a lot less toe out and less camber as the excessive toe out brought the ackerman convergent point forward of the axle, thus appearing to drag the inner rear wheel on turns.
is this a factor or just a red herring?

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

Varying amounts of Ackerman can change the behavior or 'pointy-ness', but I was under the impression your car was 'fine' before the accident and is now different post-accident. If so, Ackerman wouldn't be high on my suspect list. However, you could test this by dialing in a liberal dose of front toe-in and going for a short drive. If the behavior is notably changed there's a good chance its a front-end issue.

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Peace, Ron

so who didn't zero the alignment bracket that mount to the wheel!!!!
i made a three legged bracket from 2" x 1" box that clamps to my alloy wheels with an adjuster on each leg which have to be set at equal stand off, i have now set them equal so they reflect the outer edge of the rim and tightened the clamps.
these allow me to set camber, caster and toe as the box section extends fore and aft of the wheel and vertically so the camber/caster magnetic gauge can be mounted in the center

i guess i will start from the beginning.

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

i have now set the front to 5 1/2* caster, 1* camber and 1/16" toe in.
note that i have electric power steering so the caster shouldn't be too much to handle.

tomorrow i will remove the coil overs from the front and remeasure the toe at 2" below and 2" above ride height in 1/2" increments to get a picture of the bump steer.

if that turns out well i will move to the wheelbase and try to define a center line from front to back to prove the front and rear tracks are in line.

wish me luck

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

caster set at 5 1/2*, camber set at 1*, toe set at 1/8" toe in.
bump steer adjusted to change only in droop at an additional 1/8" in at 2" of droop, at 2" bump it stays as set at ride height.
i feel i must explain about all the adjusting, the reason i was testing the car when i went off was because i had changed the front geometry a little and after 2 years i could not remember what i had set it to, plus i did try to adjust it on an uneven garage floor, now i have a new shop, i spent some time setting it.

my wheelbase is equal within a 1/16" side to side so now i must set the rear caster and toe, i would like to get some diagonals but the car has to be on its wheels at ride height?
i have set the rear track equal about the chassis at the rearmost floor tube.

at some time i will make a gauge to check the thrust runs down the center of the track front to back.

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

Can you drive it? Is it improved?

5.5 caster is seemingly low. I originally started at 5.5. There was very little self centering and the car was a handful on fast straights. At elevated speeds steering effort was ridiculously light and the smallest of ripples in the road would push it around. I then stepped up to 7.5 and it was much improved but still a bit ‘fidgety’. I’m currently at 10 and it feels like a completly different car. Holds a line with very little effort and self-centering is dramatically improved. The dynamic weighting of the steering feels much more natural, at 5.5 mid-corner feedback was a little numb-ish, now mid-corner feedback is fantastic - more grip and more confidence both. Your power steering changes things somewhat as most systems have additional damping so outside forces aren’t as influential. Still, I think there is benefit in more caster than you’re currently running. I certainly wouldn’t hesitate to try 7 to 9 degrees.

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Peace, Ron

the power steering does dampen the feel a bit because you are turning an electric motor, this applies to the feed back in that bumps need to move the motor as well.

i have driven the car, it tracks straight and has some self centering.

i dropped a line to the ground from the lower rear outer swivel and the lower front ball joint to the ground on both sides, what do you know, they both measured 105 1/2", i also measured from the same points parallel to the axis of the chassis , passenger side was 94 1/2" and drivers side was 94 3/8", but i think this is close enough.

i will now try and measure the rear toe and camber which is difficult as there is a car in the way

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

Did you try my suggestion, jacking up the car and wiggling each tire back and forth? This method would best locate something that could cause the "twitchy" feel you're describing. Like I said earlier, "twitchy" implies something changing on its own during a drive, probably at the back. Any slop in the A-arms, rod ends, or wheel bearings could cause it. A 0.010" looseness at the inboard end of the suspension could possibly translate to a lot of toe change out at the tire.

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

KB,

i did try moving the rear around but no play was evident and i have just fitted new heim joints to all the rear pivots and all the bolts were tight.
after i set my marks on the floor i move the car but it aligned with my marks when i pushed it back in spot on

however, the rear was supposed to be set at 1/8" tow in but was in fact toed in 1/4" on the passenger side and the drivers side was toe out 1/8" but as i now have a center line, i equalized it to be 1/16" per side toe in.

i originally aligned the rear with the sides of the chassis but on the passenger side it was difficult due to the exhaust so i guess that is where i made a mistake.

camber was 1* negative on both sides.

i found a center between the front ball joints and the rear outer pivots, joined the points down the center of the marks, then i pulled the diagonals which did indeed cross on that center line so i am confident that the car is square.

it's raining now and i am just about dead from the humidity, i'm too old for this crawling under a car especially with a bad shoulder so i will drive it tomorrow, fingers crossed.

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

took it for a long drive today about 2 hours on many types of road, the road that i have been using for tests is i would say average but the car copes with it well.

it drives like a bag of marbles!!!! on any main highway

when on a main road that has truck ruts it is all over the place and is undrivable, it's down right dangerous over 50 mph.
it was so bad that i stopped at advance autos a bought some spanners to make emergency adjustments to the caster, trying to get a bit more in there but as you adjust the caster you are undoubtedly adding in bump steer.

got home safely but very tired with arms the size of my friend Jack's leg.

think i should start again, front to back.

RTz, i will try a lot more caster and re check everything else, it will take some time due to the humidity, i'm in Florida and i'm an old fart

this getting old thing is really bad, everything aches, back, knees, shoulders and hands, mentally i think i am still here but memory absolutely sucks. i have to get my wife out in the shop to write down measurements because i can't remember something for 10 seconds.
how is it i can remember exactly how to do something but can't remember the measurements when doing it and don't get me started about stupid interrupting phone calls because my warranty is about to expire on my 23 year old Jaguar or selling the time share in the Bahamas i don't have.

p.s. what tire pressures do you run? i would tell you what size tires i am running but i can't remember

lost it for a bit there, now i know how Tesla must have felt in his latter years.

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

Well John you know you can always lean on us guys when you need to vent, we don't take it personally
In fact I'm starting to relate to some of the things you've mentioned.
At least you still have persistence, you'll get the car figured out

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Perry

'If man built it, man can fix it'
"No one ever told me I couldn't do it."
"If you can't build it safe, don't build it."

Perry's Locost Super Che7enette Build
Perry's TBird Based 5.0L Super 7 L.S.O
Perry's S10 Super 7 The 3rd
Perry's 4th Build The Topolino 500 (Little Mouse) Altered
Perry's 5th Build the Super Slant 6 Super 7
Perry's Final Build the 1929 Mercedes Gazelle

If you’re confident in your alignments and your confident there’s nothing structurally wrong with the car (including bushings, ball joints, wheel bearings, and the like), then I gotta ask, are you sure your tires aren’t garbage? I’ve driven on some damn scary tires, not often but I’ve experienced genuinely crazy behavior more than once. It’s not always things you can see, it can be internal failures.

Don’t get me started on tire pressures. Okay, fine, too late… I can’t run the pressures that I want. Todays tires just aren’t made for our light cars, and my tires are no exception. I can’t drop the tire pressure low enough to optimize the contact patch without risk of a bead failure. But in your situation I wouldn’t expect any gross problems like you’re describing at any reasonable pressure (17 to 25 hot).

Sorry to hear about the aging complications. I’m not quite there, but I’m definitely not the man I used to be.

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Peace, Ron

Since toe was measured as okay, something's changing while driving.

How much play is there in the steering? Confirm that the steering rack is firmly mounted, the U-joints in the steering shaft are properly mounted and have no play, and that the tie rods are not loose.

Have you considered having someone else drive the car for a second opinion?

Tires seem doubtful since they were "fine" before, but swap them front to back as a test.

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

am i confident in my alignment?, well at this point no i am not, at least not in the guy who is doing the alignment, ME!!!! unfortunetly i don't have anyone i can trust with a good knowledge of the problem to assist

the tires thing, yes i will move them front to back and vice versa.

i will start with re checking the diagonals as if the car is not square everything else is moot.

next the rear alignment, camber and toe about the center line and also the wheel base, if this is correct, it moves any fault to the front.

the steering shaft thing, i may need to remove the side body panel on the drivers side to do this thoroughly but needs may, i will leave this until all adjustments are made and repeatable after a drive.

i will again check all the hiems and upper and lower ball joints for play

caster angle, i will add caster to 10 degrees from the 5 1/2 i "think" i have now.

i will set the camber at 2 degrees on both sides, i can compensate for road camber later if needed.

i will set toe at 1/8" in as this is a good ball park to start.

then the specter of bump steer which doesn't make me relish the task.

the statement that"it didn't do it before", sorry, but i have changed so much and so much time has gone by, i am at a point where i don't trust myself so i will repeat every step i take until i know that what i think i set it at is in fact what it "IS" set at, you know, set it, check it, drive it, check it again !

i may also remove the electric power steering just in case, as the motor puts a drag on the column making it difficult to diagnose any binding or stiffness.

i have another steering rack so i may rebuild that and swap it out but we are getting into the realms of desperation then.

thanks for your help guys, i don't know where i would be without you

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.