Mustang wheels misalignment left and right

[akmon]

I want to update this thread.
Finally I´ve installed my new wheels with a more aggresive offset. I´ll make the introduction in the proper section.
But in the issue of the misalignment still remains in front and rear. I´ve gone to 2 workshops to get the alignment. The first one said the machine that everything is perfect, the camber, toe etc. But I wanted to be sure that tha car stands over a flat surface.
So I went to another alignment machine, a Hunter, laser, quite new. The car mechanic told me a lot of negative camber on rear right side but he tried to remove some without success. I wonder how was he able to substract negative camber with the car stand. Nor with pliers is possible to do that.
"Miraclely" after driving it a while to check the behaviour, raised the car to the hunter machine again and the values are more or less better than the values he saw when bringing the car (I can´t confirm cause the didn´t allow me to see to get into the work place).
To resume: here is the list they gave me. The car behaves well, but stetically, as the new offset is outer, my eyes go to the rear wheel fender where with a ET38 it´s flush on the left side and 3,5 mm inwards on the right side. Nothing has changed on this I suppose the right side is correct, and the left side has less negative camber, but papers don´t say that. Maybe subframe misalignment?
I´m not sure whtat to do, if going to Ford dealer to see if they can correct it or living it til I´ll get used to it. Note that I chose a squared option with ET35 front. When I swap de wheels I´ll have right side flush and left side poke 3,5 mm.
Caida: camber
Convergencia: toe
tras: rear
del: front

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[Norm Peterson]

Camber changes of a hundredth of a degree can happen when other adjustments are made, like the correction of front toe that appears to have been made.

Your rear cross-camber of 0°24' amounts to somewhere in the vicinity of 3.5mm in/out at the top of your tire. Since you need 0°24' more negative on the left rear to match the right rear, that would pull the top of the LR tire about 3.5mm inward.

The car drives OK because the tolerance on cross-camber is greater than 0°24'. So what you've got now - functionally - is "good but not truly great". The good news is that fixing the left-rear camber to be like the RR camber should also fix the appearance.


Norm

 

[akmon]

Camber changes of a hundredth of a degree can happen when other adjustments are made, like the correction of front toe that appears to have been made.

Your rear cross-camber of 0°24' amounts to somewhere in the vicinity of 3.5mm in/out at the top of your tire. Since you need 0°24' more negative on the left rear to match the right rear, that would pull the top of the LR tire about 3.5mm inward.

The car drives OK because the tolerance on cross-camber is greater than 0°24'. So what you've got now - functionally - is "good but not truly great". The good news is that fixing the left-rear camber to be like the RR camber should also fix the appearance.


Norm

Thanks, Norm, for writing.

Yes, I was thinking about it, because if you apply basic triconometric: poke= 703*tan(0,24º)= 2,94 mm. So that should fix the issue.
But the problem is that the mechanic said that the left camber adjustement was on the limit of the travel: he couln´t do more camber. How is it possible, only -1,16º?

Sometimes I think alignment is like a mistic science where everybody says that his machine and point of view are the best of the place. I´m not sure if this guy told me the truth or he couldn´t move the left camber "axis" for being stuck since it went out from factory.

Don´t know if going to Ford dealer, but the advanced me if the parameters are on green they´re not going to touch anything.

 

[Norm Peterson]

Thanks, Norm, for writing.

Yes, I was thinking about it, because if you apply basic triconometric: poke= 703*tan(0,24º)= 2,94 mm. So that should fix the issue.
But the problem is that the mechanic said that the left camber adjustement was on the limit of the travel: he couln´t do more camber. How is it possible, only -1,16º?

There is 'crosstalk' between rear camber and rear toe, probably a fair amount where adjusting one also changes the other. For your left rear achieving the toe setting may have put a limit on camber adjustability. I think starting out by putting the toe adjuster near its midpoint (or possibly offset the other way a little) might free up a bit more camber adjustment. That's my understanding of multi-link rear suspensions in general.


Norm

 

[akmon]

Just to continue collecting wheels alignment machines, today I´ve been in another recommended by other luxury workshops. The machine brand is Corghi, from Italy. It´s said that cars like Porsches, Ferraris and Maserati go to this workshop for alignment.
My purpose was to gain a few decimals degrees on the left wheel to hide those 3,5 mm and being equal to the right one.
But after alignment, the guy told me that no camber adjusting is neccesary. Just only adjusting the toe could reach the necessary camber to be equal and "on the green". He said that if I want to hide those 3,5 mm then the parameters will be wrong and tire wear will be a disaster.
So here I am with another list, everything is ok, and his advise was: "forget about that nitpick thing. 3,5 mm is almost noticiable, just only by you, and noone else, the car is perfect fitted, beautiful and ready to enjoy.
The issue with this is: how the hell many of the values that mark as "before" adjusting has nothing to see with the previous alignment shop? Only 2 or 3 values. Why are so many differences? Everybody says that his machine is the best. And in this case, as the "before" camber was similar, he only had to adjust the toe and the camber was increased a conservative but good value and quite balanced. Only the toe was with high values before and now are ok (by the way, the toe (convergencia) is measured in mm. I thought it was measure in degrees). Look at the picture.

I´m starting to convince myself to live with this little flaw. Nobody is going to fit the camber because there is nothing to fit. Time to end with this story and save money because too much spent on these tests. Maybe the subframe alignment is the fault. But here, in Spain, it´s very difficult to find someone to try to adjust it.

 

[Norm Peterson]

But after alignment, the guy told me that no camber adjusting is neccesary. Just only adjusting the toe could reach the necessary camber to be equal and "on the green".

I can picture how - in theory - this could be possible.

He said that if I want to hide those 3,5 mm then the parameters will be wrong and tire wear will be a disaster.

Out of curiosity, did the 3,5 mm change to a slightly lower number? Moving left-rear toe outward should have pushed the top of the left rear tire in. Not the full 3,5 mm, maybe half a mm down to 3,0? That's if you can even measure that closely and that your setup area really is close to being as flat and level as an alignment-rack.

So here I am with another list, everything is ok, and his advise was: "forget about that nitpick thing. 3,5 mm is almost noticiable, just only by you, and noone else, the car is perfect fitted, beautiful and ready to enjoy.

I agree with that advise. Once you're moving, you won't be able to see it yourself, and once you're going at much speed nobody else is going to notice it either with camber constantly varying as the suspension moves (it's almost always moving at least a little even over what looks like flat pavement).

Keep in mind that what you're seeing also depends on how good the sheetmetal is . . . even production tolerances on chassis dimensions are subject to a couple mm tolerance, and sheetmetal tolerances are likely looser still.


Norm

 

[akmon]

I can picture how - in theory - this could be possible.


Out of curiosity, did the 3,5 mm change to a slightly lower number? Moving left-rear toe outward should have pushed the top of the left rear tire in. Not the full 3,5 mm, maybe half a mm down to 3,0? That's if you can even measure that closely and that your setup area really is close to being as flat and level as an alignment-rack.

I agree with that advise. Once you're moving, you won't be able to see it yourself, and once you're going at much speed nobody else is going to notice it either with camber constantly varying as the suspension moves (it's almost always moving at least a little even over what looks like flat pavement).

Keep in mind that what you're seeing also depends on how good the sheetmetal is . . . even production tolerances on chassis dimensions are subject to a couple mm tolerance, and sheetmetal tolerances are likely looser still.


Norm

It will be interesting for me how can a toe modification affects a camber. I´m a civil engineer and althought my speciality is static calculus these references like me a lot to learn.

You were right, half mm of difference has dissappeared. What is better. I´m not sure if it´s a placebo effect, but now when I look the wheels backwards I cannot feel so much difference than before. Maybe, thanks to the new toe measure the rear part of the rear wheels are inner and that change disguises the difference between left and right wheel.

I´ll take your advice too. I´ve just cancelled an appointment with Ford dealer. It will be a waste of time and money. It´s time to enjoy the car alone or with the family. Now the COVID restrictions are lower in my country, so I can go further with my car.
When I have the hub caps ready I´ll make an introduction of my new wheels, soon.

Thank you for your useful advices.

 

[Norm Peterson]

The way toe adjustments can affect camber is when (in this case) the lateral arm is not located on the axle line. You need to be visualizing in 3-D, so when you push toe outward you're also pushing the contact patch at the axle line outward. As long as the length of the upper link is held fixed, the knuckle/rotor/wheel/tire assembly must pivot in the camber sense about the upper link while it 'steers' about a line through the pivots of the upper link and the lower arm, which means that the top of the tire moves inward as it rotates in the toe sense. In your case, a little of that 'poke' is removed.

The toe link being on the 'front side' of the knuckle is not visible in this picture, but as we know it's somewhat forward of the axle line.

It's easy to assume that toe and camber are independent, but there is no requirement that they must be. You'd need to locate a lower ball joint directly under the centerline of the axle, which looks to be rather difficult here without significantly altering the rear suspension geometry (not necessarily in a good way) and requiring a stronger (read heavier) lower control arm to cope with the increased torsional loading that would result (can't move the spring/shock/sta-bar pickup point very much because there's an axle in the way of where you'd like to put at least two of them).


Norm

 

[akmon]

The way toe adjustments can affect camber is when (in this case) the lateral arm is not located on the axle line. You need to be visualizing in 3-D, so when you push toe outward you're also pushing the contact patch at the axle line outward. As long as the length of the upper link is held fixed, the knuckle/rotor/wheel/tire assembly must pivot in the camber sense about the upper link while it 'steers' about a line through the pivots of the upper link and the lower arm, which means that the top of the tire moves inward as it rotates in the toe sense. In your case, a little of that 'poke' is removed.

The toe link being on the 'front side' of the knuckle is not visible in this picture, but as we know it's somewhat forward of the axle line.

It's easy to assume that toe and camber are independent, but there is no requirement that they must be. You'd need to locate a lower ball joint directly under the centerline of the axle, which looks to be rather difficult here without significantly altering the rear suspension geometry (not necessarily in a good way) and requiring a stronger (read heavier) lower control arm to cope with the increased torsional loading that would result (can't move the spring/shock/sta-bar pickup point very much because there's an axle in the way of where you'd like to put at least two of them).


Norm

I confess that I have had to read your comment 4 times, but I think I know what you mean: as the length of the upper arm is fixed, when you apply a negative toe (divergence) on the wheel assembly, the upper arm system pivots slightly and as a consequence, it drops in elevation (red arrow) and produces an increase in negative camber.

 

[Norm Peterson]

I confess that I have had to read your comment 4 times, but I think I know what you mean: as the length of the upper arm is fixed, when you apply a negative toe (divergence) on the wheel assembly, the upper arm system pivots slightly and as a consequence, it drops in elevation (red arrow) and produces an increase in negative camber.

No, the contact patch moves outward by around half the amount of linear toe rod length adjustment. In front view, this produces rotation in the camber direction, with the upper link's outer pivot as the center of this rotation and resulting in inward movement at the top of the tire.

Tire top inward movement resulting from tiny vertical movement of the upper link's outer pivot is going to be on the order of hundredths of a mm at best.


Norm

 

[akmon]

No, the contact patch moves outward by around half the amount of linear toe rod length adjustment. In front view, this produces rotation in the camber direction, with the upper link's outer pivot as the center of this rotation and resulting in inward movement at the top of the tire.

Tire top inward movement resulting from tiny vertical movement of the upper link's outer pivot is going to be on the order of hundredths of a mm at best.


Norm

Aaah, ok, now I caught it, as the toe is going to divergence, the contact patch goes outer, and the outer it goes, the inner goes the top of the tire with the outer link pivot as the center of that rotation. For that reason that half mm has dissappeared.

 

[Norm Peterson]

Norm

 

[akmon]

I´ve introduced the new wheels in this post if you want to see them: https://www.mustang6g.com/forums/th...nce-of-the-mustang.139459/page-3#post-2916059

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