Sway bars, anti roll bars

[AdamR28]

Cool beans. Glad I'm not alone in enjoying this nerdy stuff! Ha 

I'll have a do at bashing the MR2 in my spreadsheet then, see what pops out...

Nowt wrong with a bit of wheel lift IMO... here's me exiting Cascades at Oulton Park doing about 80-90mph in 4th gear (on 185 section Uniroyal Rainsports!):

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A front wheel in the air just means the inside rear wheel still has plenty of load on it = traction for days 

[tets]

Cool beans. Glad I'm not alone in enjoying this nerdy stuff! Ha 

I'll have a do at bashing the MR2 in my spreadsheet then, see what pops out...

Nowt wrong with a bit of wheel lift IMO... here's me exiting Cascades at Oulton Park doing about 80-90mph in 4th gear (on 185 section Uniroyal Rainsports!):

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A front wheel in the air just means the inside rear wheel still has plenty of load on it = traction for days 

Looking forward to the numbers!!

Great pic that is and nothing wrong with Rainsports, I have a set for wets as do a lot of the race lads!

[Petrus]

Right, the Sportivo legs are under.
The ´ride´ hight ís a bit lower but static less than 10mm. and the springs are slightly firmer hence I put the ´ride´ between brackets.
Did do a shake down run and nothing shaked. The ride quality is definitely better but will do nothing remótely quick till I have the allignment sorted, hopefully Monday.

Nów I want the sway bars sooner ofcourse   

Also looking forward to some MR2 numbers in your table Adam. I lóve numbers as it quantifies the science, making  it easier to ´get´ and it provides a solid base for settings to depart from unlike the proverbial wet finger in the air 

[Petrus]

Found spring rates:

kg/mm                Front       Rear
Stock                  1.3        2.1
Sportivo               1.6        3.4

Note that the Sportivo rear springs have over double the rate of the front ones whereas the stock rear springs under half more.
TRD ´race´ springs are 2.4 and 4.7 kg, following the doubling of the rate.
Spirit S Asano san also advises this ratio for street set up although he suggests 5 and 10 kg. I dó now understand why he did not ungrade the front sway bar!!

Now the striking thing is that after market springs follow the stock ratio, just stiffer, ending up with the front stiffer than Sportivo and the rear softer.

That sure makes sway bar settings (for stock ratio or TRD ratio) different!

[tets]

Found spring rates:

kg/mm                Front       Rear
Stock                  1.3        2.1
Sportivo               1.6        3.4

Note that the Sportivo rear springs have over double the rate of the front ones whereas the stock rear springs under half more.
TRD ´race´ springs are 2.4 and 4.7 kg, following the doubling of the rate.
Spirit S Asano san also advises this ratio for street set up although he suggests 5 and 10 kg. I dó now understand why he did not ungrade the front sway bar!!

Now the striking thing is that after market springs follow the stock ratio, just stiffer, ending up with the front stiffer than Sportivo and the rear softer.

That sure makes sway bar settings (for stock ratio or TRD ratio) different!

I'm on TTE springs which after much research seem to be approx the same spring rates as stock, just 30mm lower

[Petrus]

I'm on TTE springs which after much research seem to be approx the same spring rates as stock, just 30mm lower

By Jove, that is sériously less dynamic ride hight then :-O  How much tyre rubbing do you experience?

[Ardent]

TTE springs before and tein S now.
Rubbing on stock size rims and tyres = zero.

[tets]

yep - no rubbing for me either

[Petrus]

I had some before with OEM ride hight!! and still have now: Going véry fast trough a corner and hitting a depression/bump will have it rub a moment. Will reduce with the nagative camber and no doubt also with stiffer sway bars.
Silly speed level I will admit and nothing on the smooth. Very little smooth here though, especilly up and down:
Going up after down sees the car pressed down. Have that going fast through corner and... rubs.
A more tricky one is the crown between going up and down. The car gets lighter and has less traction. Have that going fast through a corner and... you prefer oversteer to understeer 

Have a mail to Whiteline outstanding; would like to know the % of torsional stiffness between the adjustments. Easy enough to calculate if I could méasure the bar but as I don´t have them quite yet...

[Petrus]

Have received answer from Whiteline and they included a pdf with a cross ref chart.

The front bar is 146 175
The rear bar is  165 207 257 316

Thus front stiffest hole, rear softest hole would be equal to TRD Sportivo.

As a rule of thumb, LSD makes a step stiffer possible at the rear. The Spirit car obviously has LSD.
Asano san´s setting of the car is stock front, Cusco rear; 100 / 260. 

[AdamR28]

Those numbers look... odd. Be interesting to see if my calculations match up! I'll let you know.

[Petrus]

Those numbers look... odd. Be interesting to see if my calculations match up! I'll let you know.

They look awfully stiff.
The Whiteline pdf is clear though and it matches with the differences in diameters.
Mind that I take the stock braces as 100/100.
That makes 47% stiffer 147.
Hence 207, 207%, twice as stiff.
The rear though... uffff!

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[AdamR28]

Link here for anyone who has a set and wants to run the numbers more quickly than I can!

https://balancemotorsport.co.uk/suspension/anti-roll-bars

Edit: Just seen the PDF... I think we can pretty much ignore that, too generic.

[Petrus]

Edit: Just seen the PDF... I think we can pretty much ignore that, too generic.

It is only for the values of the settings of the Whiteline bars. It is where the stiffness values I updated come from.

[Petrus]

Link here for anyone who has a set and wants to run the numbers more quickly than I can!

https://balancemotorsport.co.uk/suspension/anti-roll-bars

There is one aspect missing: The angle of the link rod with the arm. At 90 degrees the torsional force is the most direct, largest. As the angle increases a larger part gets vectored alóng the rod, straining, pulling or pushing the bushing on the frame and that part of the force is not resulting in torsional resistance.
This, the angle resulting in force on the bushes, is why with extreme stiff bars/setting the mounting cán shear off.

[AdamR28]

I would guess that's too negligible to make much difference? Certainly with rod end type drop links and the sorts of angles we are talking about.

[Petrus]

I would guess that's too negligible to make much difference? Certainly with rod end type drop links and the sorts of angles we are talking about.

Just had a look at the stock set up and a virtual hole either way would be in the order of 2 degrees.
Add another hole and make it 4,5 degrees on for calculatings sake 90 = 5%, indeed not an issue.

Also noticed a glitch in my reading of the pdf. Will need to have another look when back from the garage.

[AdamR28]

Done part of 'the numbers' today, using a handy website called vSusp. Some of these values plug into the ARB calc I have, then some numbers that come out of the ARB calc can plug back in here to figure out if suspension improvements can be made.

I take no responsibility for any of this being a load of old cobblers, it's hard to measure accurately and a few mil here and there can make a big difference - BUT in general it works out as I would expect: Toyota knew what they were doing, and lowering the car is bad! Bad for body roll, bad for camber correction, bad for handling (both steering feedback and 'snappy rear end').

This is pretty tech, apologies for all the numbers. I've tried to annotate to explain best I can.

Some wording used:

Roll centre: A theoretical point, derived from the suspension geometry, through which the loading acts during cornering. Green dot on vSusp.

Roll axis inclination: Imagine a line drawn from the front roll centre, to the rear roll centre. This is the roll axis.

Roll couple: The distance (and direction) between the roll centre and the centre of mass of the car. Think of it as a lever - force (the car being acted on by lateral acceleration) x distance (the distance between the centre of mass and the roll centre). This is based upon an estimated CoG height of 18" for a standard car.

A large roll couple - therefore a low roll centre - will transfer the loads more through 'soft' items (springs and dampers) and a lower roll couple (a high roll centre) will do it more through the length of the solid suspension components / lower arm. The same comes about when the roll couple either acts in the same direction as cornering force, or the opposite, due to roll centre migration in the horizontal direction. You can then imagine that lower roll centres (and ones which have migrated in the opposite direction to cornering loads) make the car feel 'squishy' in body roll, and high roll centres (and those migrated in the same direction) make it feel 'snappy'.

Camber correction: When the car rolls over, the ideal is that both tyres are kept upright (or at least as close as possible to the static camber value). Double wishbone systems are better than Mac Struts at doing this (when designed half-right!).

A note: There is some real weirdness going on with the rear roll centre after the car has been lowered around 20-25mm or more (when using my measurements - therefore it is possible due to measuring errors that this tipping point could be 35mm, for example, especially if toyota themselves offer a kit which lowers the car 30mm). At this point the roll centre location actually reverses the direction in which it migrates compared with standard ride height during body roll  (in both X and Y directions) - this will absolutely explain 'snappy' rear ends.

The diverging roll centre migration front to rear in both X and Y planes at standard ride heights (and maybe down to -30mm ish, depending on accuracy of my measurements as explained above) may explain why our cars seem to benefit so much from chassis bracing. Each end is trying to do something quite different, so stiffening the chassis will be felt drastically.


So here we go:

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The links for the suspension setups are as follows...

Standard ride height:

http://vsusp.com/#0.8%26project_name%3Adefault%20values%26trim%7Bbody_roll_angle%3A0%7Cfront.left_bump%3A0%7Crear.left_bump%3A0%7Cfront.right_bump%3A0%7Crear.right_bump%3A0%7D%26front%7Bframe.susp_type%3A1%7Cframe.bottom_y%3A15600%7Cframe.center_to_upper_mount_x%3A54700%7Cframe.bottom_to_upper_mount_y%3A58000%7Cframe.center_to_lower_mount_x%3A36200%7Cframe.bottom_to_lower_mount_y%3A2800%7Ccontrol_arms.upper_length%3A24800%7Ccontrol_arms.lower_length%3A33900%7Cknuckles.hub_to_upper_x%3A15000%7Cknuckles.hub_to_lower_x%3A7000%7Cknuckles.hub_to_lower_y%3A10000%7Cknuckles.hub_to_upper_y%3A13000%7Cknuckles.hub_to_strut_axis%3A19500%7Cknuckles.strut_incl%3A8700%7Csteering.active%3A1%7Csteering.hub_to_outer_tie_rod_x%3A6500%7Csteering.hub_to_outer_tie_rod_y%3A6000%7Cwheels.offset%3A4500%7Cwheels.diameter%3A1500%7Cwheels.diameter_expl%3A35000%7Ctires.size_convention%3A0%7Ctires.section_width%3A18500%7Ctires.aspect_ratio%3A5500%7Ctires.diameter_expl%3A50000%7Ctires.width_expl%3A7620%7Ctires.compression%3A0%7D%26rear%7Bframe.susp_type%3A1%7Cframe.bottom_y%3A16800%7Cframe.center_to_upper_mount_x%3A48000%7Cframe.bottom_to_upper_mount_y%3A63000%7Cframe.center_to_lower_mount_x%3A30400%7Cframe.bottom_to_lower_mount_y%3A2500%7Ccontrol_arms.upper_length%3A24800%7Ccontrol_arms.lower_length%3A37800%7Cknuckles.hub_to_upper_x%3A15000%7Cknuckles.hub_to_lower_x%3A9000%7Cknuckles.hub_to_lower_y%3A10000%7Cknuckles.hub_to_upper_y%3A13000%7Cknuckles.hub_to_strut_axis%3A17000%7Cknuckles.strut_incl%3A7800%7Csteering.active%3A0%7Csteering.hub_to_outer_tie_rod_x%3A7620%7Csteering.hub_to_outer_tie_rod_y%3A7620%7Cwheels.offset%3A4500%7Cwheels.diameter%3A1500%7Cwheels.diameter_expl%3A35000%7Ctires.size_convention%3A0%7Ctires.section_width%3A20500%7Ctires.aspect_ratio%3A5000%7Ctires.diameter_expl%3A50000%7Ctires.width_expl%3A7620%7Ctires.compression%3A0%7D%26pref%7Bdiag1.px_per_mm%3A300%7Cdiag1.front_or_rear%3Afront%7Ctab.active%3A0%7Cunits%3A1%7Cshow.f%3A1%7Cshow.ca%3A1%7Cshow.k%3A1%7Cshow.st%3A1%7Cshow.stl%3A1%7Cshow.w%3A1%7Cshow.t%3A1%7Cshow.rc%3A1%7Cshow.rcl%3A1%7Cshow.ic%3A1%7Cshow.icl%3A1%7Cshow.fvsa%3A0%7Cshow.tl%3A0%7Cshow.kpil%3A0%7Credraw_during_drag%3A1%7Cchart.x_axis_center%3A0%7Cchart.x_axis_window%3A10%7Cchart.x_axis_num_steps%3A21%7Cchart.x_axis_field%3Atrim.body_roll_angle%7Cchart.y_axis_fields%3A%5BFR%5D.tires.left_camber%7D


30mm lowered (eg. lowering springs):

http://vsusp.com/#0.8%26project_name%3Adefault%20values%26trim%7Bbody_roll_angle%3A0%7Cfront.left_bump%3A0%7Crear.left_bump%3A0%7Cfront.right_bump%3A0%7Crear.right_bump%3A0%7D%26front%7Bframe.susp_type%3A1%7Cframe.bottom_y%3A12600%7Cframe.center_to_upper_mount_x%3A54700%7Cframe.bottom_to_upper_mount_y%3A58000%7Cframe.center_to_lower_mount_x%3A36200%7Cframe.bottom_to_lower_mount_y%3A2800%7Ccontrol_arms.upper_length%3A24800%7Ccontrol_arms.lower_length%3A33900%7Cknuckles.hub_to_upper_x%3A15000%7Cknuckles.hub_to_lower_x%3A7000%7Cknuckles.hub_to_lower_y%3A10000%7Cknuckles.hub_to_upper_y%3A13000%7Cknuckles.hub_to_strut_axis%3A19500%7Cknuckles.strut_incl%3A8700%7Csteering.active%3A1%7Csteering.hub_to_outer_tie_rod_x%3A6500%7Csteering.hub_to_outer_tie_rod_y%3A6000%7Cwheels.offset%3A4500%7Cwheels.diameter%3A1500%7Cwheels.diameter_expl%3A35000%7Ctires.size_convention%3A0%7Ctires.section_width%3A18500%7Ctires.aspect_ratio%3A5500%7Ctires.diameter_expl%3A50000%7Ctires.width_expl%3A7620%7Ctires.compression%3A0%7D%26rear%7Bframe.susp_type%3A1%7Cframe.bottom_y%3A13800%7Cframe.center_to_upper_mount_x%3A48000%7Cframe.bottom_to_upper_mount_y%3A63000%7Cframe.center_to_lower_mount_x%3A30400%7Cframe.bottom_to_lower_mount_y%3A2500%7Ccontrol_arms.upper_length%3A24800%7Ccontrol_arms.lower_length%3A37800%7Cknuckles.hub_to_upper_x%3A15000%7Cknuckles.hub_to_lower_x%3A9000%7Cknuckles.hub_to_lower_y%3A10000%7Cknuckles.hub_to_upper_y%3A13000%7Cknuckles.hub_to_strut_axis%3A17000%7Cknuckles.strut_incl%3A7800%7Csteering.active%3A0%7Csteering.hub_to_outer_tie_rod_x%3A7620%7Csteering.hub_to_outer_tie_rod_y%3A7620%7Cwheels.offset%3A4500%7Cwheels.diameter%3A1500%7Cwheels.diameter_expl%3A35000%7Ctires.size_convention%3A0%7Ctires.section_width%3A20500%7Ctires.aspect_ratio%3A5000%7Ctires.diameter_expl%3A50000%7Ctires.width_expl%3A7620%7Ctires.compression%3A0%7D%26pref%7Bdiag1.px_per_mm%3A300%7Cdiag1.front_or_rear%3Afront%7Ctab.active%3A0%7Cunits%3A1%7Cshow.f%3A1%7Cshow.ca%3A1%7Cshow.k%3A1%7Cshow.st%3A1%7Cshow.stl%3A1%7Cshow.w%3A1%7Cshow.t%3A1%7Cshow.rc%3A1%7Cshow.rcl%3A1%7Cshow.ic%3A1%7Cshow.icl%3A1%7Cshow.fvsa%3A0%7Cshow.tl%3A0%7Cshow.kpil%3A0%7Credraw_during_drag%3A1%7Cchart.x_axis_center%3A0%7Cchart.x_axis_window%3A10%7Cchart.x_axis_num_steps%3A21%7Cchart.x_axis_field%3Atrim.body_roll_angle%7Cchart.y_axis_fields%3A%5BFR%5D.tires.left_camber%7D


50mm lowered (figure a lot of track cars on coilovers would go about here):

http://vsusp.com/#0.8%26project_name%3Adefault%20values%26trim%7Bbody_roll_angle%3A0%7Cfront.left_bump%3A0%7Crear.left_bump%3A0%7Cfront.right_bump%3A0%7Crear.right_bump%3A0%7D%26front%7Bframe.susp_type%3A1%7Cframe.bottom_y%3A10600%7Cframe.center_to_upper_mount_x%3A54700%7Cframe.bottom_to_upper_mount_y%3A58000%7Cframe.center_to_lower_mount_x%3A36200%7Cframe.bottom_to_lower_mount_y%3A2800%7Ccontrol_arms.upper_length%3A24800%7Ccontrol_arms.lower_length%3A33900%7Cknuckles.hub_to_upper_x%3A15000%7Cknuckles.hub_to_lower_x%3A7000%7Cknuckles.hub_to_lower_y%3A10000%7Cknuckles.hub_to_upper_y%3A13000%7Cknuckles.hub_to_strut_axis%3A19500%7Cknuckles.strut_incl%3A8700%7Csteering.active%3A1%7Csteering.hub_to_outer_tie_rod_x%3A6500%7Csteering.hub_to_outer_tie_rod_y%3A6000%7Cwheels.offset%3A4500%7Cwheels.diameter%3A1500%7Cwheels.diameter_expl%3A35000%7Ctires.size_convention%3A0%7Ctires.section_width%3A18500%7Ctires.aspect_ratio%3A5500%7Ctires.diameter_expl%3A50000%7Ctires.width_expl%3A7620%7Ctires.compression%3A0%7D%26rear%7Bframe.susp_type%3A1%7Cframe.bottom_y%3A11800%7Cframe.center_to_upper_mount_x%3A48000%7Cframe.bottom_to_upper_mount_y%3A63000%7Cframe.center_to_lower_mount_x%3A30400%7Cframe.bottom_to_lower_mount_y%3A2500%7Ccontrol_arms.upper_length%3A24800%7Ccontrol_arms.lower_length%3A37800%7Cknuckles.hub_to_upper_x%3A15000%7Cknuckles.hub_to_lower_x%3A9000%7Cknuckles.hub_to_lower_y%3A10000%7Cknuckles.hub_to_upper_y%3A13000%7Cknuckles.hub_to_strut_axis%3A17000%7Cknuckles.strut_incl%3A7800%7Csteering.active%3A0%7Csteering.hub_to_outer_tie_rod_x%3A7620%7Csteering.hub_to_outer_tie_rod_y%3A7620%7Cwheels.offset%3A4500%7Cwheels.diameter%3A1500%7Cwheels.diameter_expl%3A35000%7Ctires.size_convention%3A0%7Ctires.section_width%3A20500%7Ctires.aspect_ratio%3A5000%7Ctires.diameter_expl%3A50000%7Ctires.width_expl%3A7620%7Ctires.compression%3A0%7D%26pref%7Bdiag1.px_per_mm%3A300%7Cdiag1.front_or_rear%3Afront%7Ctab.active%3A0%7Cunits%3A1%7Cshow.f%3A1%7Cshow.ca%3A1%7Cshow.k%3A1%7Cshow.st%3A1%7Cshow.stl%3A1%7Cshow.w%3A1%7Cshow.t%3A1%7Cshow.rc%3A1%7Cshow.rcl%3A1%7Cshow.ic%3A1%7Cshow.icl%3A1%7Cshow.fvsa%3A0%7Cshow.tl%3A0%7Cshow.kpil%3A0%7Credraw_during_drag%3A1%7Cchart.x_axis_center%3A0%7Cchart.x_axis_window%3A10%7Cchart.x_axis_num_steps%3A21%7Cchart.x_axis_field%3Atrim.body_roll_angle%7Cchart.y_axis_fields%3A%5BFR%5D.tires.left_camber%7D


And for comparison here is a double wishbone setup I designed for a single seater, based around a Mk1 Miata, which I never got round to building sadly:

http://vsusp.com/?tool=2d#0.8%26project_name%3AMXR1%26trim%7Bbody_roll_angle%3A0%7Cfront.left_bump%3A0%7Crear.left_bump%3A0%7Cfront.right_bump%3A0%7Crear.right_bump%3A0%7D%26front%7Bframe.susp_type%3A0%7Cframe.bottom_y%3A8500%7Cframe.center_to_upper_mount_x%3A38100%7Cframe.bottom_to_upper_mount_y%3A27000%7Cframe.center_to_lower_mount_x%3A32892%7Cframe.bottom_to_lower_mount_y%3A7800%7Ccontrol_arms.upper_length%3A17300%7Ccontrol_arms.lower_length%3A28000%7Cknuckles.hub_to_upper_x%3A12776%7Cknuckles.hub_to_lower_x%3A7745%7Cknuckles.hub_to_lower_y%3A8559%7Cknuckles.hub_to_upper_y%3A12344%7Cknuckles.hub_to_strut_axis%3A14000%7Cknuckles.strut_incl%3A8000%7Cwheels.offset%3A3500%7Cwheels.diameter%3A1300%7Cwheels.diameter_expl%3A35000%7Ctires.size_convention%3A0%7Ctires.section_width%3A18500%7Ctires.aspect_ratio%3A6000%7Ctires.diameter_expl%3A50000%7Ctires.width_expl%3A7600%7Ctires.compression%3A0%7D%26rear%7Bframe.susp_type%3A0%7Cframe.bottom_y%3A10500%7Cframe.center_to_upper_mount_x%3A39000%7Cframe.bottom_to_upper_mount_y%3A25200%7Cframe.center_to_lower_mount_x%3A26000%7Cframe.bottom_to_lower_mount_y%3A5900%7Ccontrol_arms.upper_length%3A19500%7Ccontrol_arms.lower_length%3A36500%7Cknuckles.hub_to_upper_x%3A15391%7Cknuckles.hub_to_lower_x%3A11907%7Cknuckles.hub_to_lower_y%3A9525%7Cknuckles.hub_to_upper_y%3A12065%7Cknuckles.hub_to_strut_axis%3A14000%7Cknuckles.strut_incl%3A8000%7Cwheels.offset%3A3500%7Cwheels.diameter%3A1300%7Cwheels.diameter_expl%3A35000%7Ctires.size_convention%3A0%7Ctires.section_width%3A18500%7Ctires.aspect_ratio%3A6000%7Ctires.diameter_expl%3A50000%7Ctires.width_expl%3A7600%7Ctires.compression%3A0%7D%26pref%7Bdiag1.px_per_mm%3A200%7Cdiag1.front_or_rear%3Afront%7Ctab.active%3A0%7Cunits%3A1%7Cshow.f%3A1%7Cshow.ca%3A1%7Cshow.k%3A1%7Cshow.w%3A1%7Cshow.t%3A1%7Cshow.rc%3A1%7Cshow.ic%3A1%7Cshow.fvsa%3A0%7Cshow.tl%3A0%7Cshow.kpil%3A0%7Credraw_during_drag%3A1%7Cchart.x_axis_center%3A0%7Cchart.x_axis_window%3A5%7Cchart.x_axis_num_steps%3A21%7Cchart.x_axis_field%3Atrim.body_roll_angle%7Cchart.y_axis_fields%3A%5BFR%5D.general.roll_center.y%7D]MXR1

Have a play with wiggling the wheels round and you will see there is very little roll centre migration, plus good camber correction under both bump and roll.

[tets]

Will have to leave this until tomorrow - had a couple of beers and it's wine o-clock now!!

[Petrus]

Thanks Adam, much obliged. Playing with it and as much confirmed as stunned.

[ralf321]

Guys, what I now don't understand at all are the dogbones. As far as I understood after playing with the settings for the lowered car from above, they seem to make things even worse.
The subframe should be lifted, not lowered.
Do I miss something ?

BR
Ralf

[Petrus]

Guys, what I now don't understand at all are the dogbones. As far as I understood after playing with the settings for the lowered car from above, they seem to make things even worse.
The subframe should be lifted, not lowered.
Do I miss something ?

BR
Ralf

Thát THE question Ralf.

Point is that the front roll centre lowers too.
Hence my thinking that they tried restore a bit of the balance. Meaning that with RC ball joints they should come out?

[Dev]

Guys, what I now don't understand at all are the dogbones. As far as I understood after playing with the settings for the lowered car from above, they seem to make things even worse.
The subframe should be lifted, not lowered.
Do I miss something ?

BR
Ralf

That is correct sir. Im happy that Boris is making them for whom ever wants to tune or try them out and this is not about harming his sales for them but they do exactly the opposite of what you want and will make things worse especially if you want to lower the car further.

[Dev]

Guys, what I now don't understand at all are the dogbones. As far as I understood after playing with the settings for the lowered car from above, they seem to make things even worse.
The subframe should be lifted, not lowered.
Do I miss something ?

BR
Ralf

Thát THE question Ralf.

Point is that the front roll centre lowers too.
Hence my thinking that they tried restore a bit of the balance. Meaning that with RC ball joints they should come out?

  I think you actually may have solved the reason for the dog bones.  It is because they were designed for the TRD Sportivo kit as a whole.  Its possible that the fronts were designed with a particular amount of lowering or the rear needed to be higher for clearance which could be due to all kinds of reasons possibly regulations, looks  or because the supplier for the springs and dampers could not get the right size and therefore the rear roll center  had to be lowered to match the front.  Toyota is quiet conservative trying to make everything safe for road use.

 This is why you shouldn't use the dog bones as a separate item without considering the entire kit or what you want to do with the car as far as a radical set up but I cant see a scenario where they are beneficial for anything but the kit. If you buy a different system there shouldn't have any benefit with the dog bones and there is a good argument to be made that it will make it worse not being able to preserve the roll center.

 if you have a set of coil overs you can set the ride height and do essentially the same thing.   

[Dev]

Double post.