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I don't think it has been mentioned yet. but your REAR toe is miles off...!
 
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Discussion Starter #22
I agree David and thanks for your comment. (y)
This will be solved in next phase. :)
Btw, I appreciated your suggestion about zero toe for front wheels year ago... :)

 

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Measured distance between upper and lower ball joint of wishbones on 147/156/GT front wheels is ≈450mm. In that sense, it is needed additional relative lateral displacement between ball joints of ≈8mm (exact is 7.85mm) for change of camber of .
Embarrassment is what I get for relying only on my memory of something that I measured quite a long time ago. From this memory I could have sworn that the distance between upper and lower ball joint centres was 360mm, but apparently my recollection was faulty and way off.

I have just now remeasured this (on my spare parts car that has no wheel or brake fitted, so access for measurement is pretty good). The tape measure tells me that the distance between the upper and lower ball centres is 520mm (+ or - just a few millimetres). Of course some estimation is required here because the balls can't actually be seen inside the joint, but estimation error will be only slight with little affect on the numbers.

Sorry for the earlier misinformation. Redoing my CorelDraw diagram with the very near to correct 520mm distance between BJ centres, I get this:

For every 10mm lateral relocation of a single BJ there is a 1.11° change in KPI and camber, so for every 1mm of BJ relocation there is a 0.11° change. It is similar if the BJ is moved longitudinally, i.e. there will be a 1.11° caster change for every 10mm of fore / aft BJ relocation.

For practical purposes this near enough to being a 10 to 1 ratio for estimating exepected camber or caster change for a given distance of horizontal BJ relocation.

I can't see where you are getting "450mm" distance between BJs from?

Regards,
John.
 

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By use of washers under two holes of strut body (see video clip from YT), it is needed washer of 3mm for achievement of lateral displacement of upper ball joint of 7.5mm what is enough for change of camber of ≈57'. That is consequence of ratio between height of aluminium cast (150mm) and distance of holes with and without inserted washers (60mm), therefore "factor of enlargement of displacement" is 150/60=2.5.
But, probably... it is only theory. Better approach is method with slotted holes, described by John and Alan.
OK, looking at the vid again, I see exactly what he has done, which is kind of clever lateral thinking (but IMO not without potential problems). I don't think the vid is particularly clear, but this might be due to how carefully I originally viewed it (maybe...). Previously I had failed to see that only two spacer washers had been inserted between the tower and the casting, and not four as I had thought I'd seen (or perhaps had just carelessly assumed..).

The spacers are fitted at the two innermost studs between casting and tower top, which 'pushes' the whole casting downward on the inner side. This tilts the casting, and also tilts everything attached to it, i.e. the upper wishbone and the top of the 'strut' itself. The upper spring seat is now at some angle relative to its' as designed position, to the angle of the top of the spring, and to the piston rod, which might or might not be a problem...

I've just finished experimenting with this modification on one side of my spare parts car, approximating the effect but without actually adding spacers and tighteneing everything down, just looking for in principle proof of concept...

I loosened the two innermost nuts to give 3mm clearance between the nuts and top surface of the tower, and just barely loosened the two outermost nuts. I then inserted a lever between the top of the casting and the underside of the tower, and prised the casting downward until the two inner nuts moved 3mm and firmly contacted the top of the tower. This more or less mimicked the effect of placing two 3mm spacers at the inner two studs (between the casting and tower, as above). This resulted in the upper ball joint moving significantly outward...

I measured the outward BJ movement at 7mm, close to the 7.5mm being claimed for fitting the two 3mm spacers as described.

In my experiment, the 3mm clearance at the inner nuts was closed by the levering against the casting and forcing it downward by 3mm, approximating the affect of the two 3mm spacers. Different changes to KPI / camber could be affected by differenty thickness washers.

But, there is an issue or two with this modification, as I see it. Because the casting is tilted at a significant angle by the insertion of spacer washers at only two studs (not one spacer at all four studs), when the four tower nuts are fully tightened the casting and the top plate of the tower will be stressed in some degree.

Inserting spacer washers at only the innermost two studs tilts the entire casting, which rotates in a shallow arc centred on an axis that is more or less defined by the upper outer edge of the casting, where this edge sits against the underside of the top of the tower plate. The two outer studs are a bit inboard of the outer edge of the casting, so that if the nuts are not tight there would be a wedge shaped gap at the stud locations between the upper surface of the casting and the underside of the tower top. There will also be wedge shaped gaps at the inner studs. When the nuts are fully tightened then the gaps will close up, with unavoidable metal distortion...

The casting and the tower plate will need to significantly distort as all four of the stud nuts are tightened. Only with such distortion will it be possible to clamp together surfaces that are in effect no longer parallel with each other (as they were designed to be), due to the tilting of the casting created by the spacers. Some of this distortion will be elastic, and some will likely be permanent deformation.

During my experimenting with this I could feel metal flexure occuring while levering the casting downward, it didn't feel very nice. I'm fairly confident that tightening the four nuts would cause more distortion than occurred while I was levering the casting...

Such distortion might or might not create significant problems, immediately or down the track, such as cracked metal. And as I mentioned above, the tilting of the upper spring seat caused by the tilting of the casting might be a problem, or might not.

So while I kind of admire the lateral thinking evident in this modification, I'm far from sure that I would do it to my car..

Regards,
John.
 

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Discussion Starter #25
Basic problem with "washer solution" is nonuniform contact between steel strut body and aluminium cast which could cause deformation and maybe failure breaking of cast (aluminium is brittle material ). Therefore "slot solution" for change of camber is emphasized as better and safer.

One dilemma remains: both of solutions change inclination of dampers (very slightly, indeed) and it could influence on driving conditions. But wrong camber has similar influence.
 

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Basic problem with "washer solution" is nonuniform contact between steel strut body and aluminium cast which could cause deformation and maybe failure breaking of cast (aluminium is brittle material ).
Yes, that is basically what I said (using many more words...).

The aluminium that the casting is made from may or may never fail as a result of the deformation. It is my understanding and experience that while some grades of aluminium can be fairly brittle, most are reasonably ductile and will bend before cracking.

Therefore "slot solution" for change of camber is emphasized as better and safer.
Is my prefferred of the two methods, just to be on the safe side...

One dilemma remains: both of solutions change inclination of dampers (very slightly, indeed) and it could influence on driving conditions. But wrong camber has similar influence.
Increasing the inclination of a 'strut' (or a spring, or a damper, or both as a 'coilover' as in this case) typically makes it behave as if it has been softened (in effect, and depending on the particular geometry of the control arms / wishbones relative to the initial strut orientation), i.e. the suspension geometry gains a little more leverage over the strut. In this instance the additional inclination will I think be way too slight to make any significant difference to ride stiffness or handling.

The affects of altered camber will be different to affects of increase or decrease in strut inclination.

Regards,
John.
 

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Discussion Starter #27
I have just now remeasured this (on my spare parts car that has no wheel or brake fitted, so access for measurement is pretty good). The tape measure tells me that the distance between the upper and lower ball centres is 520mm (+ or - just a few millimetres).
After 350mm, 360mm, 520mm... I remeasured this distance again and... it is 540mm.
This means following: use of two washer (2x2mm=4mm) makes 1° 03' change of camber.
 

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After 350mm, 360mm, 520mm... I remeasured this distance again and... it is 540mm.
This means following: use of two washer (2x2mm=4mm) makes 1° 03' change of camber.
I have no idea where I got 360mm from, it just popped into my head as the recalled length. If I think about it at all it doesn't even make sense, it is obviously way too short...

My measurement BJ ball to BJ ball is 520mm, and I can't see that I would have an 'estimation error' of anywhere near 10mm per BJ (to make 540mm, as you have it). I suspect you might be mis-estimating where the centres of the balls are inside the joints? It is the centre of each ball in the joint that is the centre of articulation and so defines the steering axis, and so the nominal measurement point defining the location of the BJ. Not that I think it is all that important, for practical purposes 20mm won't make a significant difference to the 10 to 1 ratio.

According to my on car experiment, 3mm of vertical movement at the inner side of the casting (i.e. 3mm downward at the two inner studs) results in a 7mm horizontal BJ movement. Using the 10 to 1 ratio for horizontal BJ relocation, this indicates that the negative camber should increase by 0.7° (with 3mm of washer thickness). Divide this by three to find the degree change per mm of washer thickness, and we get 0.23° camber change for every 1mm of washer thickness.

So according to this, using 4mm of washer thickness at both inner studs will give 0.92° camber change (0.23° x 4 = 0.92°). Your figure for a 4mm washer thickness is 1°4' (1.05°) of camber change, so for all intents and purposes may as well be considered exactly 1°. My number is also pretty very close to 1° camber change, so I think we are near enough to being in more or less complete agreement (at least quite close in a small ballpark...).

I still woudn't adjust my camber using this method...

Regards,
John.
 

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Discussion Starter #29 (Edited)
After all explanations and arguments I prefer "slot method" too. It does direct translation of upper wishbone ball joint to proper position for change of camber. Maybe "slot method" needs much more activities, but it minimizes risk that things go in mechanically unsafe side.
Combination of this method and use of "eccentric bushes" (camber change kit) makes possible achievement of +/- change of camber.
 

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One dilemma remains: both of solutions change inclination of dampers (very slightly, indeed)
Looking at this more closely;
The coilover (i.e. damper / spring unit) will only incline more if the part of the casting which holds it (i.e. the 'dome') moves laterally when the spacer washers are inserted. This doesn't happen, the 'dome' moves vertically and not laterally (at least not to any remotely significant degree).

This is because the underside of the 'dome' locates the upper part of the of the coilover, and the 'dome' is located directly between the two studs to which the spacer washers are fitted. Due to being in this position relative to the spacer washers, the 'dome' only moves vertically when the washers are installed, so the inclination of the coilover won't be affected by the camber 'washer adjustment'.

What will happen when the spacers are installed;
The chassis will sit a bit higher above the top of the coilover (i.e. higher by the thickness of the spacer washers). And, the tilt angle of the coilover spring seat will change slightly in accordance with the degree to which the casting has become tilted by insertion of the spacer washers.

A 'to scale' CorelDraw diagram tells me that the casting and upper spring seat will tilt by roughly 3.5° or so (I can't be precise with this number due to some degree of expected casting and tower flexure etc, but this ought to be a close enough approximation).

This angle change of the upper spring seat will affect the way the top of the spring is loaded. Some load will be moved from one side of the spring to the other side, and so cause the coils to become less evenly compressed. In other applications I have seen this to cause coils to rub against one side of the damper, while moving further away from the damper on the other side, i.e. the spring curving away from the damper on one side while curving toward it on the other side (and this gets worse the more the spring is compressed).

In theory this 'curving' of the spring can make the effective spring rate significantly non linear, even if the spring has a nominally linear rate (i.e. may affect how stiffly / softly the spring behaves, whether it is a linear or progressive spring).

The diameter of the top spring coil is very close to 100mm. With this dimension, CDraw tells me that if the upper spring seat is tilted by 3.5° then one side of the top coil will move upward by 3mm, and so the spring will become somewhat decompressed on that side, relative to the other side. The other side of the top coil will move downward by 3mm, and so the spring will become more loaded on that side (this would be the side to rub against the damper, if that happened).

These potential affects may or may not be great enough in a given instance to cause significant issues in the real world and with a given car...

Regards,
John.
 

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Discussion Starter #31
I appreciate these arguments and warnings, but described phenomenons affect behaviour of coilover in driving conditions only in small extent. Only take in consideration following facts: both ends of coil isn't full circle (i.e. direct action of force is in small part of coil) and top end has enough diameter to avoid friction with damper.

Only difficulty and possible problem with "washer solution" is possibility of break failure of aluminium cast, because of nonuniform support conditions between steel chassis and aluminium cast. It is sufficient reason to avoid "washer solution" in comparison with "slot solution". Btw, I hope that my "eccentric bushes" (see picture) will be enough to compensate wrong camber configuration, especially because this solution makes possible easy change in any moment without previous drilling and grinding works. Unfortunately, this more safe and easy solution is more expensive.

947278
 

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i found this from a thread years ago on alfa156net:

947324


i must say that was good thinking by inserting washers under rear screws, i would do it but with wedge shaped metal pieces to get bigger surface on strut.

I think the measurements were poor because car was not level, and every time car goes from lift it has to be moved a little so that suspension settles, and steering must be dead on straight.
 

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The distance between the ball centres of the two BJs is significantly less than 560mm. The 560mm measurement in the photo is from the very bottom to the very top of the upright forging, which is not the same as the distance between the two ball centres.

In vertical position, the upper BJ ball sits higher than the top of the upright forging. In the photo (upright lying on its' side) the upper BJ ball would be somewhat to the right of the end of the red arrow. With the upright again in the vertical position, the lower BJ ball is located well above the lowest part of the upright forging, within that large squarish hole. In the photo (with the upright lying on its' side), the lower BJ is to the right of the left end of the red arrow.

The lower BJ is quite a bit larger than the upper BJ, so sits higher above the lowest part of the forging compared to the height of the upper BJ ball joint above the top of the casting. This is why the distance between BJ ball centres is not the same as the distance between the very top and very bottom of the upright forging.

Regards,
John.
 

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The side to side difference in front camber & caster could simply be down to the subframe shifting sideways.
So a subframe alignment could cure that.

I'd be concentrating first on the rear toe....
Currently you have one rear pointing in and the other pointing out...!!
That will be causing the car to crab sideways.
It likely needs the adjustment points on the subframe where the transverse arms connect cleaning up.
Sadly many alignment places are lazy and try to convince people that the rear isn't adjustable... it IS adjustable and yours needs sorting out.
 
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I'd be concentrating first on the rear toe....
Currently you have one rear pointing in and the other pointing out...!!
That will be causing the car to crab sideways.
It likely needs the adjustment points on the subframe where the transverse arms connect cleaning up.
Sadly many alignment places are lazy and try to convince people that the rear isn't adjustable... it IS adjustable and yours needs sorting out.
Left side rear toe is technically toed-out, but it might as well be 0° (it's just so close it doesn't matter). Right side is 0.27° (0°16') which translated to linear mm measured at the tyre faces is 2.9mm toe-in, so near enough 3mm of total rear toe-in, which isn't excessive.

The fact that it is unequal side to side means that there is a 'thrust angle' oriented to the left. The thrust angle is half the total rear toe, which the report (in post #1) has the thrust angle at 0°.9', and I have at 0.15° (the same as a decimal angle).

The thrust angle will cause the car to 'crab', i.e. the rear wheels will track slightly to one side of the front wheel tracks. When the car is travelling in a straight line the chassis will be at a slight angle to the direction of travel (i.e. 0.15°), and the steering wheel will slightly off centre (assuming there are no other issues affecting steering wheel orientation).

But it isn't necessarily as bad as it might sound. According to Greg Locock (a very credible engineer who used to work for Lotus and Ford); "Thrust angle is primarily an aesthetic requirement, that is to say, a visually horrible amount of thrust angle (say 1 degree) will have no perceptible effect on the behaviors of the car". This cars' thrust angle is nowhere near that.

Having said this, I'd get it seen to next time you get it aligned, but IMO it's not a big problem as it stands.

Regards,
John.
 

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Discussion Starter #36 (Edited)
Sadly many alignment places are lazy and try to convince people that the rear isn't adjustable... it IS adjustable and yours needs sorting out.
It isn't laziness but impossibility of rear toe adjustment because the alignment crew is stuck by corrosion. It will be sorted in local workshop by use of high temperature and WD40 treatment what will release stuck alignment crew.
Btw, equalisation of front cambers needs 2.04mm displacement of a whole sub frame in right direction (i.e. to in).
 

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Btw, equalisation of front cambers needs 2.04mm displacement of a whole sub frame in right direction (i.e. to in).
I think that is easily than near enough, even if it doesn't agree exactly with my numbers..

My numbers:
Current front camber (from the report sheet) is:
Left camber = -2.05° (-2°03')
Right camber = -1.6° (-1°37')
Cross camber = 0.45°

To equalise cambers both wheels need to be adjusted by half of the cross camber (i.e. 0.45° / 2 = 0.225°). Using the 10 to 1 ratio (10 millimetres of BJ relocation for every degree of camber change), the left wheel needs a 0.225° reduction in neg camber, the right wheel needs a 0.225° increase in negative camber. Moving the subframe to the right by 2.25mm will do this well enough (in theory, according to my CoreDraw diagram).

The camber would then be 1.825° on the left and 1.825° on the right, so cross camber will be 0.0°, i.e. the cambers will be exactly the same left and right (and then they will change as soon as the driver gets in the car...).

These numbers are different to what I said in my post above (#35, I have deleted the errors). I must have become confused while in a state of tiredness...

------------------

So what would happen if the subframe were moved by your 2.04mm instead of my 2.25mm?

Camber on both sides would change by 0.204°.
So:
Left camber would change from -2.05° to -1.846° (0.204° decrease in negative camber)
Right camber would change from -1.6° to -1.804° (0.204° increase in negative camber)
Cross camber would be 0.042°, which is insignificant...

Regards,
John.
 

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Discussion Starter #38
@alan Q4+33, @David C and @johnlear, could you suggest some technically acceptable way for equalisation of cambers by displacement of subframe in proper side in amount of 2mm? :)
 

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@alan Q4+33, @David C and @johnlear, could you suggest some technically acceptable way for equalisation of cambers by displacement of subframe in proper side in amount of 2mm? :)
Dusan,
It isn't rocket science, you just need to be methodical.

Put the car on a hoist if you can, or on chassis stands if you have to (it might be possible on ramps, not sure). Get underneath and loosen all the bolts that attach the subframe to the body / chassis. This is most of the the bolts that you can see on the underside of the frame (and a couple you might not see, don't 'not see' the two bolts at the top of the two vertical 'legs' of the frame). All the bolts point upward. You want the subframe to be loose but not lowered, so just crack the bolts loose enough.

Exceptions; Don't loosen the eight bolts attaching the lower wishbones to the subframe. It isn't essential to loosen the two bolts holding the steering rack to the frame, or the four bolts holding the anti roll bar (but it wouldn't hurt so if in doubt crack them loose).

Now find a point where a suitable robust pry bar can be inserted between the subframe and some part of the chassis in a manner that permits the subframe to be prised to the right. If you can't find somewhere to prise the frame, then it can be given a few whacks with a heavy soft mallet, or drifted with short length of wood (i.e. wood against frame, hit wood with big hammer...).

Tech tip; before starting all this, mark the subframe and a corresponding mark on the chassis so that you can tell if the frame has moved and by how much. The frame will not move a great deal, there isn't a large amount of clearance between the OD of the bolt shanks and the ID of the subframe crush tubes through which the bolts pass. It is also quite possible that the frame might not move at all, the bolt to tube clearance may already be 'used'.

Regards,
John.
 

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Discussion Starter #40 (Edited)
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