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Lowering the rear ride height (relative to the front) won't cause the rear end to carry significantly more weight. Don't be confused by the fact that forward acceleration causes rear end squat as well as rearward weight transfer, the two aren't inextricably linked, rather they are two somewhat seperate affects of the acceleration.

Statically raising or lowering one end of a car relative to the other will move weight (represented by the CG of mass) forward or rearward, but only to a relatively small degree (even if the change in relative ride heights were to be quite substantial). It will be measurable in single digit millimetres, and of itself I can't see that this small change in static longitudinal weight distribution will have a significant effect on the handling or steering etc.

Out of curiosity (and to quantify my assumptions...) I made a CorelDraw diagram. According to the diagram, if we assume a chassis with a wheelbase of 2595mm (156 sedan wheelbase), with a CG height at 600mm (about the same as the top of the tyres, generally a reasonable rough approximation of CG height), and a 60% forward weight bias determining the longitudinal CG location (typical FWD), then a 30mm lowering of rear ride height causes the CG to move backward by only 7mm (note that the CG also lowers by 12mm). This represents only a 2.7% change in the front / rear static weight bias (with a 30mm rear ride height lowering).

This is not to say that changing relative front / rear ride heights won't affect handling and steering, but I can't see that it would be as a direct result of altering the longitudinal weight distribution so slightly. The change in CG height will be more significant, as will the associated change to the height of the rear vs front geometric roll centres.

Lowering the rear GRC (as will occur with a reduction in rear ride height, quite possibly significantly more than the actual decrease in ride height), will decrease geometric rear roll stiffness, so will reduce lateral weight transfer at the rear (while causing lateral WT to increase at the front even if front roll stiffness is unaltered). This will tend to increase understeer, especially initial understeer because geometric weight tranfers are 'instant' as opposed to 'mechanical' weight tranfers which are 'slow' ('geometric' being the % of weight transfer which occurs via the suspension geometry, and 'mechanical' being the % of WT which occurs via the springs and ARBs).

IMO it is probably counter productive for the rear ride height to be reduced if the front ride height isn't (likely to be understeer inducing, as well as degrading responsiveness to steering inputs and change of direction), so I do agree with you that you should try to avoid it happening. I just don't agree with the notion that it is a product of any change in static weight distribution...

Regards,
John.

Well that makes total sense to me now. A very deep view into the subject, never considered the geometry factor in question. I haven't confirmed in depth that the front / rear height ratio has changed, since i haven't noted the height before the modification.
Plus, there's another variable on this issue that i didnt mentioned before. I've powerflexed the rear end some days after the suspension upgrade. It was part of a maintenance solution and i'm pretty happy with the feel plus already passed two years and fortunately the rear camber is still the same today as it was the day i've made the bushings maintenance. The powerflex bushings on the rear turned it more precise, stiff and grippy. It could be this that is making it less grippy at the front in comparison. One thing is fact, i feel more understeer in initial turn and less after the initial turn. Plus with the 2.4 bar F / R not only the front lacks response as the tyres get chewed pretty easy. My last Toyos got totally bald on the interior in 8000/9000kms while the center still almost new. Now with 2.6 front and 2.4 rear the new Conti are wearing evenly and the initial turn in understeer almost gone.

Supposedly this B12 should work fine and the rear / front measures are according to what is expected after installation. So thinking once again about it, it could be the rear powerflex stiffening everything up influencing on the geometry response between back and rear. I have planned to powerflex the front as well considering that i'm so pleased on the effect and compliance on the rear. I might have another reason to do it now.
 

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I haven't confirmed in depth that the front / rear height ratio has changed, since i haven't noted the height before the modification.
Just keep in mind that lowering the rear ride height also lowers the rear GRC, and this can impact handling and steering response. When lowering I think it's generally advisable to ensure the rear lowering is no greater than the front lowering, or less than the front lowering. I would always keep lowering ambitions modest, as lowering usually messes with the geometry in ways that may not be obvious.

Plus, there's another variable on this issue that i didnt mentioned before. I've powerflexed the rear end some days after the suspension upgrade. It was part of a maintenance solution and i'm pretty happy with the feel plus already passed two years and fortunately the rear camber is still the same today as it was the day i've made the bushings maintenance. The powerflex bushings on the rear turned it more precise, stiff and grippy.
I've fitted custom made rear lateral control arms on my 147. These are based on Toyota Corolla and Camry rear control arms, and eliminate the relatively soft Alfa control arm bushes (note that my cars' 'original' rear control arms appeared to be in good condition, but may have been aftermarket and not OE, and there is some suggestion that at least some aftermarket rear arms have problematically softer bushes than OE arms). Each control arm is a hybrid of half a Camry arm and half a Corolla arm (one or both shortened to suit the length required for the Alfa). The Camry arms use a spherical bearing at the outer end (factory part, fully weather sealed etc). The Corolla arms have rubber bushings, but much stiffer than the Alfa bushings. So, each hybrid arm has a spherical outer bearing and a fairly stiff rubber inner bush. The arms are also tubular, eliminating the flimsy 'U' shaped Alfa arm stamping. A search on this forum for 'Camry' and / or 'Corolla' should find a more in depth description. These arms were a huge improvement in rear end stability, probably similar to what you have achieved with fitting poly bushes (maybe better, can't really say).

It could be this that is making it less grippy at the front in comparison. One thing is fact, i feel more understeer in initial turn and less after the initial turn. Plus with the 2.4 bar F / R not only the front lacks response as the tyres get chewed pretty easy. My last Toyos got totally bald on the interior in 8000/9000kms while the center still almost new. Now with 2.6 front and 2.4 rear the new Conti are wearing evenly and the initial turn in understeer almost gone.
Personally I've found that very high tyre pressures work very well to sharpen up the handling and steering response (what most people would probably regard as 'excessive' pressures...). The pressures I'm using are substantially higher than you are using (arrived at with a lot of experimentation). The down side is harshness, but the car is much more fun to drive.

My cars' steering response is good with some toe-in, and the tyre wear is very even across the treads. Toe-out will promote inner edge wear (when negative camber is also present). I'm using 3mm of toe-in both front and rear, and prefer the steering feel of toe-in compared to toe-out (which I find makes the car a bit 'wandery' without really improving turn in response, despite what seems to always be said regarding toe-out...).

Supposedly this B12 should work fine and the rear / front measures are according to what is expected after installation. So thinking once again about it, it could be the rear powerflex stiffening everything up influencing on the geometry response between back and rear. I have planned to powerflex the front as well considering that i'm so pleased on the effect and compliance on the rear. I might have another reason to do it now.
Softer bushings in the rear control arms adversely affect steering response, as well as handling 'precision'. Also, when the bushes are laterally loaded the bushes in the frontward control arms (front arms of the rear suspension) compress more than the bushes in the rearward control arms. This is because the arm geometry laterally loads the frontward arms more heavily than the rearward arms, not because the bushes in the front arms are softer, all eight bushes in the four arms are same stiffness (many cars also use softer bushes in the front arms compared to the rear arms). This creates a passive steer effect which induces rear toe-in when cornering. This passive steer is understeer inducing (i.e. 'stabilises' the handling by inducing understeer...). The softer the bushes the greater this affect will be.

I have standard bushes in the front suspension lower control arms. I'd like to try stiffer bushes (poly being the only practical option for this), but it's a lot of expense for something which may cause more trouble than it's worth...?

Regards,
John.
 

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Just keep in mind that lowering the rear ride height also lowers the rear GRC, and this can impact handling and steering response. When lowering I think it's generally advisable to ensure the rear lowering is no greater than the front lowering, or less than the front lowering. I would always keep lowering ambitions modest, as lowering usually messes with the geometry in ways that may not be obvious.



I've fitted custom made rear lateral control arms on my 147. These are based on Toyota Corolla and Camry rear control arms, and eliminate the relatively soft Alfa control arm bushes (note that my cars' 'original' rear control arms appeared to be in good condition, but may have been aftermarket and not OE, and there is some suggestion that at least some aftermarket rear arms have problematically softer bushes than OE arms). Each control arm is a hybrid of half a Camry arm and half a Corolla arm (one or both shortened to suit the length required for the Alfa). The Camry arms use a spherical bearing at the outer end (factory part, fully weather sealed etc). The Corolla arms have rubber bushings, but much stiffer than the Alfa bushings. So, each hybrid arm has a spherical outer bearing and a fairly stiff rubber inner bush. The arms are also tubular, eliminating the flimsy 'U' shaped Alfa arm stamping. A search on this forum for 'Camry' and / or 'Corolla' should find a more in depth description. These arms were a huge improvement in rear end stability, probably similar to what you have achieved with fitting poly bushes (maybe better, can't really say).



Personally I've found that very high tyre pressures work very well to sharpen up the handling and steering response (what most people would probably regard as 'excessive' pressures...). The pressures I'm using are substantially higher than you are using (arrived at with a lot of experimentation). The down side is harshness, but the car is much more fun to drive.

My cars' steering response is good with some toe-in, and the tyre wear is very even across the treads. Toe-out will promote inner edge wear (when negative camber is also present). I'm using 3mm of toe-in both front and rear, and prefer the steering feel of toe-in compared to toe-out (which I find makes the car a bit 'wandery' without really improving turn in response, despite what seems to always be said regarding toe-out...).



Softer bushings in the rear control arms adversely affect steering response, as well as handling 'precision'. Also, when the bushes are laterally loaded the bushes in the frontward control arms (front arms of the rear suspension) compress more than the bushes in the rearward control arms. This is because the arm geometry laterally loads the frontward arms more heavily than the rearward arms, not because the bushes in the front arms are softer, all eight bushes in the four arms are same stiffness (many cars also use softer bushes in the front arms compared to the rear arms). This creates a passive steer effect which induces rear toe-in when cornering. This passive steer is understeer inducing (i.e. 'stabilises' the handling by inducing understeer...). The softer the bushes the greater this affect will be.

I have standard bushes in the front suspension lower control arms. I'd like to try stiffer bushes (poly being the only practical option for this), but it's a lot of expense for something which may cause more trouble than it's worth...?

Regards,
John.
Thanks for the feedback John. I'm not using 2.4bar these days. In fact i'm using 2.6 front and 2.45 rear for the reason you've mentioned. It gets stiffer but the car feels much more alive and reduces any minor perceived floatiness that i can feel when driving very hard with 2.4 all around. With 2.6 it just handles perfectly even when close to lose grip on the tyres. I dont use the same pressure always because the car rests on the building garage where is always around 15ºC, in summer days i use to put the pressure down to 2.5Front and 2.4R as cold, because its so hot outside and the road its so hot that i would end up with a very high pressure after driving for about 20/30minutes. So i use a lower pressure in order to avoid that effect. During the rest of the year is when i use 2.6/2.45

I live in Portugal and here during the summer we get peaks of 42ºC, most of the year is around 10-22ºC.
The problem is, in my garage the even in the hotter summer days the temperature doesnt reach 20ºC, so its not the best cold temp reference to drive after in 40ºC conditions.
 

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Already fitted Eibach ARBs but noticed that the rear ARB doesnt sit centered. The right side (Uk driver side) drop link is pulled for the center of the car, while the left side link pulls toward the wheel. So it sits uneven.

What is even more weird is the fact that the bar has to limiter rings that fix around the bushing so... the only possibility is the bar being instaled inverted to fix the issue. Trying to figure out that with my mechanic. This was installed in another shop...
 

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Assuming we're talking about the same thing, I also found that the Eibach 'limiter rings' were positioned in the wrong place to enable the rear ARB to sit centrally. From memory, my mechanic grinded the weld, re positioned the ring and re-welded. This enabled the bar to locate centrally and the drop-links to be vertical, not at an angle.
 

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Assuming we're talking about the same thing, I also found that the Eibach 'limiter rings' were positioned in the wrong place to enable the rear ARB to sit centrally. From memory, my mechanic grinded the weld, re positioned the ring and re-welded. This enabled the bar to locate centrally and the drop-links to be vertical, not at an angle.
exactly it just seems that the limiter rings are positioned too far from the corner making the bar be positioned more to the left (looking from behing)

we’re also considering the possibility of the subframe being a bit shifted to the left side. Since the bar is attached to the subframe, the issue could be on the subframe instead of the bar. Will compare the Eibach with the old original one.
 

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Assuming we're talking about the same thing, I also found that the Eibach 'limiter rings' were positioned in the wrong place to enable the rear ARB to sit centrally. From memory, my mechanic grinded the weld, re positioned the ring and re-welded.
Soo,
A locating ring (flange) was cut off and relocated on the bar by rewelding it directly to the bar? This is dubious practise, the bar will be affected by welding heat, which may create a very sharply defined change in the nature of the steel at and near the weld.

The hot metal can be quickly cooled by its' proximity to the relatively very cold metal adjacent to the weld, ie. the heat conducts from the weld into the cold bar, possibly quickly enough that the weld and / or bar metal that was very hot a moment or two ago becomes hardened. There is a reasonable chance that there will be an abrupt change in hardness adjacent to the weld, which could create a stress riser that could lead to the bar failing. A similar problem could be caused by welding rod metal becoming included into the matrix of the ARB steel, the two metals won't be metalurgically the same and their state will be a lot different one to the other. Then again, you might get away with it...

This enabled the bar to locate centrally and the drop-links to be vertical, not at an angle.
ARBs can be laterally fixed in position with only a couple of hose clamps. The clamps are tightly fitted to the ARB, with a clamp each side of one of the 'D' bushes (i.e. one clamp loosely abutting each side of a D bush). This method could have been used above, i.e. just grind off the existing flanges and replace their function with clamps each side of one of the D bushes. This would have had zero affect on the existing bar material.

If I had an ARB that was not centred (and I have had, more than once), the first thing I'd ask myself would be whether or not this is actually a real problem. Does it cause any part to interfere with any other parts as the suspension rises and falls? Is either of the drop links at an unacceptable angle? (the drop links will most likely tolerate a substantial degree of angularity, and uneveness of angularity side to side).

If the answer to these questions was 'no', then IMO centering the ARB is very unlikely to be worth the hassle, especially as it will have at most a marginal affect (if any) on the roll stiffness (either more or less stiff than if the ARB was truly 'on centre').

Regards,
John.
 

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I find just fitting GTA ARBs to my 156 good enough. Fitting the rear ARB alone is a good enough upgrade but obviously fitting both is the best option.

I'm sure the Eibach route is great but I fail to see on a financial basis alone whether it's worth it.
 

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Soo,
A locating ring (flange) was cut off and relocated on the bar by rewelding it directly to the bar? This is dubious practise, the bar will be affected by welding heat, which may create a very sharply defined change in the nature of the steel at and near the weld.

The hot metal can be quickly cooled by its' proximity to the relatively very cold metal adjacent to the weld, ie. the heat conducts from the weld into the cold bar, possibly quickly enough that the weld and / or bar metal that was very hot a moment or two ago becomes hardened. There is a reasonable chance that there will be an abrupt change in hardness adjacent to the weld, which could create a stress riser that could lead to the bar failing. A similar problem could be caused by welding rod metal becoming included into the matrix of the ARB steel, the two metals won't be metalurgically the same and their state will be a lot different one to the other. Then again, you might get away with it...



ARBs can be laterally fixed in position with only a couple of hose clamps. The clamps are tightly fitted to the ARB, with a clamp each side of one of the 'D' bushes (i.e. one clamp loosely abutting each side of a D bush). This method could have been used above, i.e. just grind off the existing flanges and replace their function with clamps each side of one of the D bushes. This would have had zero affect on the existing bar material.

If I had an ARB that was not centred (and I have had, more than once), the first thing I'd ask myself would be whether or not this is actually a real problem. Does it cause any part to interfere with any other parts as the suspension rises and falls? Is either of the drop links at an unacceptable angle? (the drop links will most likely tolerate a substantial degree of angularity, and uneveness of angularity side to side).

If the answer to these questions was 'no', then IMO centering the ARB is very unlikely to be worth the hassle, especially as it will have at most a marginal affect (if any) on the roll stiffness (either more or less stiff than if the ARB was truly 'on centre').

Regards,
John.
About the drop links.
The angle they get considering the bar positioning wouldn't affect the torque required to twist the bar on that specific side?

i have a problem of assymetric behaviour on the car. Dont know if its this issue with the bar that is doing that or the instalation on the front bar that required the subframe to come down and while putting it in place they didnt centered it properly...

About the rear bar what really worries me its not so much of it rubbing the body, which we solve pretty easily, but how that lack of centrality could change the way the bar work side to side. I want the behaviour at the left to be as close of the behaviour at the right.

AD887065-FE07-45FE-B2EB-11F7A69DDDF2.jpeg
AD887065-FE07-45FE-B2EB-11F7A69DDDF2.jpeg 3E406F77-7C7D-4D27-A396-4604BB364DC1.jpeg B5059E93-A8C0-443D-884C-D8CBC5C52414.jpeg
 

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About the rear bar what really worries me its not so much of it rubbing the body, which we solve pretty easily, but how that lack of centrality could change the way the bar work side to side. I want the behaviour at the left to be as close of the behaviour at the right.
If I understand you correctly, I think you're worrying about something which is a non issue. It doesn't matter if the ARB is not centred, or if the drop links are not at identical angles, or even if the ARB arms are of different length. The roll stiffness imparted by an ARB always acts symmetrically regardless of whether these things are also symmetrical, or not.

As an example, if we make the ARB arms adjustable (in length), and we make one arm shorter than the other, then what happens is that the ARB as a total entity becomes equally stiffer to forces acting and reacting at both ends of the bar. This is because a force acting at one end of the ARB bar is braced against the resistance at the other end of the bar, and is not being braced against a fixed resistance (fixed resistance would be the case if the bar were reacting directly against the chassis itself, in which case the bar would become a torsion bar spring rather than an anti roll bar).

This turns out to be a bit difficult to explain clearly and concisely. The important point is that an ARB with unequal length arms, or unequally angled drop links, will still be 'seen' by the chassis as equally stiff whether the car is negotiating a left or a right hand turn, so roll stiffness and so weight transfer characteristics will be equal in both left and right hand turns (all esle being equal).

This can be used as a tuning feature for adjustable ARBs, e.g. if a small change in roll stiffness is required and changing the lengths of both arms will be too much of a change, then a smaller stiffness adjustment can be achieved by just changing the length of only one arm. This doesn't make the bar behave asymmetrically, it will still be and act with the same stiffness in left and right hand turns.

Regards,
John.
 

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i have a problem of assymetric behaviour on the car. Dont know if its this issue with the bar that is doing that or the instalation on the front bar that required the subframe to come down and while putting it in place they didnt centered it properly...
I very much doubt that your asymmetric handling and / or steering (or what?) is caused by anyrthing related to the front or rear ARBs. It will be something suspension related not being symmetrical, IMO probably not ARBs but more likely to be something like a worn bushing, maybe unequal cambers casters etc, or maybe a number of small asymmetries stacking up. Or maybe tyre related...?

Can you describe the 'asymmetry' in the cars behaviour?

Regards,
John.
 

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Misalignment of subframes is definitely possible though, but you need to get alignment of the wheels checked and look at SAI/camber and caster angles to work it out for the front, and camber angles for the rear. Can be a case of moving the subframe 2mm and re aligning wheels to get it fixed.
 

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I very much doubt that your asymmetric handling and / or steering (or what?) is caused by anyrthing related to the front or rear ARBs. It will be something suspension related not being symmetrical, IMO probably not ARBs but more likely to be something like a worn bushing, maybe unequal cambers casters etc, or maybe a number of small asymmetries stacking up. Or maybe tyre related...?

Can you describe the 'asymmetry' in the cars behaviour?

Regards,
John.
I'm also planning to adress the subject in that matter. Next Thursday i will be with an Alfa Specialist that works on alignment and will do the 4wheel alignment with subframe repositioning.

Its clear that whats happening has influence from the alignment, i was just wondering if the anti-roll bar could also have influence or not, on this subject.


I have this issue a long time ago, before changing all the rear bushes (which now are powerflex) and the front arms, so i guess it will be really a subframe shift. I started to feel this assymetry after changing the front original ARB to another OEM ARB while doing a suspension refresh one year after buying the car, 5 years ago more or less. So 4 years trying to figure this thing out. Every shop that i went refused to align with the subframe.

About the car behaviour. At speeds above 140kmh i feel the car roll much more when i corner to the right. Coincidently the left negative camber is more pronounced than the right negative camber at the front, and at the back its the oposite. The left side has more negative camber than the right side.

Those are the specs of my last alignment.

About the sheet. The translation.
The upper "Cáster", "Câmber" and "Convergência" (Toe) refers to the front, the other (camber, convergência) below refers to the rear. Esquerda is Left, Direita is Right.
Screen Shot 2020-05-23 at 17.30.16.png
 

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I don't see the subframe shift in those numbers. i wouldn't attempt to fix such low differences Check the dampers for gas pressure, or try to check corner balance. Also make sure the arb droplinks aren't pulling when stationary.
 

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I don't see the subframe shift in those numbers. i wouldn't attempt to fix such low differences Check the dampers for gas pressure, or try to check corner balance. Also make sure the arb droplinks aren't pulling when stationary.
I have those differences before changing all the arms and dampers. I have B8 with Pro Kit all around everything with less than 2 years. In the meantime ive changed the dampers and springs from side to side in order to clarify if that would be the issue. The behaviour hasnt changed. Dampers, arms, antiroll bar, springs, everything was changed. The car started to behave like this after changing the antiroll 4 years ago. And at the time the subframe came out for the instalation. the car didnt in my hands and the behaviour changed after having the car, its its unlikely to be a bent chassis. Ive hit a pothole 2 years ago but it was on the opposite side, so if the damper was damaged wouldnt affect the opposite side in this way.

the subframe seems to me to be the only loose end.
 

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I don't see the subframe shift in those numbers. i wouldn't attempt to fix such low differences Check the dampers for gas pressure, or try to check corner balance. Also make sure the arb droplinks aren't pulling when stationary.
Drop links and bars have months. All installed at the same time.

To clarify, its not only a turn in problem. It feels simply a weight transfer issue. Like the undercarriage of the car is uneven with the body.
It happens on the turn in, mid and corner end. Its more noticeable at high speed.

Its nothing huge, but im a bit sensitive with the handling.
 

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I could be wrong, but, my suspicion is that it may have been around the time that your anti roll bar was replaced (which one?) that you first noticed a problem(?). To rule the suspect ARB in or out, perhaps try temporarily disconnecting one of the drop links, see if the asymmetric roll becomes unbiassed...

It seems like you have changed most things in the suspension, and the geometrical asymmetries you have given (camber, caster) are quite minimally different. I doubt it is a geometrical problem.

I have chased a subtle steering pull to the left in my 147 from soon after I bought the car. The steering felt a touch lighter steering left vs right. The car was more responsive right vs left. The handling was OK in either direction, but wasn't symmetrical in that it didn't feel the same in left vs right turns (either way was good enough, just felt like a slightly different car left vs right, a subtle affect, but I'm sensitive...).

I tried everything I could think of. Wheel aligned to symmetric settings repeatedly (I do my own alighments), to no significant affect. In desperation I also tried:

Asymmetric camber alignments where one side had up to 1° more negative camber than the other (I can adjust right side camber with slotted holes, to match whatever left side camber might be). Conventional wisdom says that the steering will pull toward the side with the least negative camber, but I was not been able to reduce the left biassed steering pull by making the left side negative camber greater than the right side camber. The tyres seem fairly insensitive to camber, at least how it affects a steering pull...

Asymmetric caster angles, up to 1° more caster on the left than right (I can change caster on the left side with slotted holes, to match whatever right side caster might be). Conventional wisdom says that the steering will 'pull' toward the side with the least caster, but this is not in my experience with this car where up to 1° less caster on the right side does not create a pull to the right, or even lessen an existing pull to the left.

Asymmetric thrust angle (to left and to right).

Aligned it with and without a driver equivalent mass in the drivers' seat. No substantial difference, but I do like it a bit better after aligning with driver weight accounted for (possible placebo...).

Corner weighted the car (as far as is possible, it can never be equally weighted left vs right).

Swapped tyres around, and new tyres.

Made adjustable ARB drop links front and rear, so all preload could be removed from the ARBs.

Made adjustable rear control arms to make rear camber adjustable, also with Toyota spherical rod ends and much stiffer Toyota rubber bushes (than the quite soft OE Alfa bushes).

Replaced any part which was obviously suspect or seemed possibly suspect. With one exception, the left side lower control arm seemed fine when on the car, ball joint was tight and both bushes seemed stiff when pried with a lever, but when I took it off the car the rear bush was in bad shape (damned thing did seem fine on the car...).

This turned out to be the main problem, at least the steering pull has gone since replacing the arm and it's offending bush. After all this effort and other things I have done, the handling is now amazingly good, for a fat FWD hatchback...

I have learnt some things along this journey;

Modern radial tyres seem quite 'numb' to camber angle. Setting my 147 up to have quite asymmetric side to side camber made no significant difference to the steering feel or handling. I suspect that car companies might request the tyre companies to design tyres that are relatively insensitive to camber, which would explain how the car companies get away with not providing camber adjustment these days. The stiffer the sidewall the more camber sensitive a tyre probably tends to be, but most radial tyres have pretty soft sidewalls...

Corner weight changes of quite a substantial nature have little discernible affect on how the car feels steers or drives, much to my surprise.

ARB preload has less affect than one might expect, i.e. very little.

At least some cars seem quite 'numb' to a significant difference in left and right caster angle. I suspect this may be related to scrub radius, i.e. if SR is near zero then the car will probably be relatively unaffected by unequal caster.

Regards,
John.
 

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Speculative food for thought;

The driver sits offset well to one side of the chassis. As a result he / she experiences roll motion not only as an angular change in the 'levelity' of the chassis platform, but also as an associated rise or lowering of the seat height. The driver will subconsciously sense the dynamic rising as opposed to the dynamic lowering of the seat, not the height itself (i.e. is the seat moving up, or is it moving down?).

This is because the driver is NOT located on (or even close to) the same axis around which the body roll motion actually occurs (BTW this is not the 'roll axis' because there are hardly any circumstances in which body roll actually articulates around the geometric 'roll axis' as defined by the front and rear 'roll centres', but that is a massive other discussion...).

The car body will respond to lateral force by 'rolling' in an arc which is centred on an axis of roll (again this is not the more or less mythical 'geometric roll axis', but an axis that is at most only partially defined by the front and rear geometric roll centres). Consider that the driver is offset from the axis of actual roll motion, above and to one side of it, and to a different side depending on the direction of turn. Because the driver is offset to one side of this axis, he / she will be moved either up or down as the body rolls, depending on which way the corner turns.

In left and right hand turns the driver will either rise more than he / she lowers (when the car is turning in the ther direction), or lower more than he / she rises, because when roll occurs one side of the chassis gets lower to the ground, the other side gets higher off the ground, and this tends to be an unequal height change.

So all else being equal, because the driver is substantially offset to one side of the chassis, if enough roll motion occurs the driver will experience a greater change in height related movement (a rise or a lowering). The driver will sense either 'up' or 'down' motion, but also the 'up' will be more than the 'down' or vice versa, depending corner direction and the dynamic specifics of the particular chassis.

I suggest that with this non equal behaviour in left vs right hand corners (of any theoretical point being offset from the chassis centreline), that it may well be possible for a driver to percieve the degree of body roll and therefore the level of roll stiffness as being different in left vs right hand corners, even if the roll stiffness and roll motion is actually quite symmetrical...?

I suspect that as roll stiffness increases (so less actual roll motion), that the scope for such a possibly incorrect perception of roll stiffness being unequal left vs right would diminish.

So is it possible that your problem is only a percieved roll stiffness asymmetry caused by the laterally offset position of the driver?

As I said above, this is all just speculation on my part.

Regards,
John.
 

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Speculative food for thought;

The driver sits offset well to one side of the chassis. As a result he / she experiences roll motion not only as an angular change in the 'levelity' of the chassis platform, but also as an associated rise or lowering of the seat height. The driver will subconsciously sense the dynamic rising as opposed to the dynamic lowering of the seat, not the height itself (i.e. is the seat moving up, or is it moving down?).

This is because the driver is NOT located on (or even close to) the same axis around which the body roll motion actually occurs (BTW this is not the 'roll axis' because there are hardly any circumstances in which body roll actually articulates around the geometric 'roll axis' as defined by the front and rear 'roll centres', but that is a massive other discussion...).

The car body will respond to lateral force by 'rolling' in an arc which is centred on an axis of roll (again this is not the more or less mythical 'geometric roll axis', but an axis that is at most only partially defined by the front and rear geometric roll centres). Consider that the driver is offset from the axis of actual roll motion, above and to one side of it, and to a different side depending on the direction of turn. Because the driver is offset to one side of this axis, he / she will be moved either up or down as the body rolls, depending on which way the corner turns.

In left and right hand turns the driver will either rise more than he / she lowers (when the car is turning in the ther direction), or lower more than he / she rises, because when roll occurs one side of the chassis gets lower to the ground, the other side gets higher off the ground, and this tends to be an unequal height change.

So all else being equal, because the driver is substantially offset to one side of the chassis, if enough roll motion occurs the driver will experience a greater change in height related movement (a rise or a lowering). The driver will sense either 'up' or 'down' motion, but also the 'up' will be more than the 'down' or vice versa, depending corner direction and the dynamic specifics of the particular chassis.

I suggest that with this non equal behaviour in left vs right hand corners (of any theoretical point being offset from the chassis centreline), that it may well be possible for a driver to percieve the degree of body roll and therefore the level of roll stiffness as being different in left vs right hand corners, even if the roll stiffness and roll motion is actually quite symmetrical...?

I suspect that as roll stiffness increases (so less actual roll motion), that the scope for such a possibly incorrect perception of roll stiffness being unequal left vs right would diminish.

So is it possible that your problem is only a percieved roll stiffness asymmetry caused by the laterally offset position of the driver?

As I said above, this is all just speculation on my part.

Regards,
John.
That would be valid and makes all the sense but i don’t think this is the case. The reason i think its not the case its because of the timing of the turn in is also different. And to me personally its a big difference. Its not only the motion, its the road feeling. I feel the outer front wheel to be very light during corner, not planted, which is strange. Normally i feel the stress on the body on the outer side. And at low speed that is the case. This happens mostly at high speed. Its like the car floats into the direction.

I’ve already wondered if it was something like tyre sidewall flex. I was running Toyo Proxes T1 Sport at the 4 wheels but recently put new Pilot Sport 4s at the rear and the rear Toyos came to the front. Will change them in the meantime because they’re also reaching the acceptable minimum. But if it was the case it would be equal in both cornering directions.

when i bought the car i felt it rolling more than now. The body roll now is substancially reduced when turning left. While turning right i dont feel the front as a block pointing to the direction but instead the front diving in an angular motion to the corner. The car grips but i don't feel it planted.
Never felt this on any car before so its quite disconcerting.

Now one thing that you said that made me wonder is about the left lower arm. The upper arms were changed at the same time but the lower ones didn’t. Being the left one, the oldest. It could be a possibility. I know... it should be changed on pairs. But at the time one of them was starting to knock and the other was new. I also noticed that when i’ve changed the lower arm, the caster value raised on the alignment.

It could be the case that if the arm bushings being worn, the arm could allow for a great camber only during compression...?

Another insteresting detail is that the left side is about 3mm lower compared to the right one. This after the proceidure we’ve done to the right damper lower fitting. We noticed that the right damper were incorrectly installed on the shop and it wasn’t properly sitting on the lower circunference. It was bolted in position but the damper has space to go down. We putted it right and the previous 9mm are now only 3mm. I wonder if driving for about 2years with uneven ride height (tilted to the left) could put enough stress to cause a premature wear on the left arm.
 

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Semi random thoughts and blather arising from your statements and questions:

Front camber can be affected if the front lower control arm bush is badly worn. Camber is affected if this bush is compressed or deforms under load because these things will cause the lower ball joint to move in or out relative to the chassis. This bush (if worn / damaged) will have very little if any affect on caster angle, because the lower ball joint doesn't move backward or forward due to LCA front bush damage / wear.

Note that it is concievable for this bush to have become softened with age while still being correctly concentric when only lightly loaded. So, lack of unusual static camber doesn't necessarily indicate that the bush is OK. This bush if old / damaged / softened will likely suffer from excessive compliance and deformation under load, allowing erratic camber change with varying lateral loadings in use.

The other LCA bush is of course the rear one. If damaged / worn this bush will have little to no affect on the static camber, but is likely to have a significant affect on the caster angle. When worn / damaged / softened this bush allows the rear end of the LCA to move in and / or out. This doesn't allow the lower ball joint to move in and out, but instead allows it to move backward and forward, thus changing the caster angle.

The same applies to this bush as to the other, i.e. the rear LCA bush can be soft but still reasonably concentric, so correct static caster doesn't necessarily prove that the bush is OK. On the other hand, if the bush or entire arm is replaced with new and the caster changes, then it is a good bet that the old bush was not in good shape.

If one LCA has already been replaced quite recently then it should not be necessary to replace it again just because you are now changing the other one and it is considered 'best practise' to always replace suspension parts in pairs. If the LCA is still reasonably newish then the two bushes should still be perfectly OK, and ought not to have softened appreciably enough to cause a significant asymmetry, or need to replace what is not a particularly cheap part.

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IMO tyre pressure seems very tyre sensistive. I have found that many tyres seem to work a lot better at quite high psi (or at least feel better, if by "better" we mean more responsive and fun to drive with), while others don't seem to need nearly as much. Tyres with less stiff sidewalls (i.e. most tyres) generally seem to require quite high pressure to be reasonably responsive, while 'sportier' tyres with relatively stiffer sidewalls (and treads to some degree) tend to be stiff enough at a lower psi, and higher pressure than that doesn't really seem to improve them.

Currently I have 44psi in my rear tyres and 39psi in the front tyres. Over the years of much experiment I have generaly found that I prefer it when I have more pressure in the rear tyres than the front ones.

I prefer higher psi in my road car tyres than most people, because I prefer a very responsive feel and behaviour. If I was racing on the same tyres I might not use quite such high pressure because as the pressure passes Xpsi the grip tends to decrease at least somewhat (while steering and handling response increases).

Horses for courses and everthing is a compromise. On the race track all that matters is what lowers the lap times, but on a 'sporty' road car we also want it to be responsive, sharp and fun to drive...

Regards,
John.
 
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