Like a dog with a bone

[1979scotte]

Hope you're not asking me not got a clue

[Petrus]

Hope you're not asking me not got a clue

Ok, send me yours and I´ll try for free :-))

[Joesson]

This was discussed in the thread ending here :
https://www.mr2roc.org/forum/index.php?msg=836158

I see that in #73 you mention you changed ´just the ball joint´.
Further on I read OEM DIY refurbishing too.
Also read Dev commenting that on some cars they cannot be removed.
Hmmm....
Just ´want´ to swap the ball joints and not get into a complex going for more expensive still project.

#73 was to do with a Ford Fiesta Track rod end ball joint where I was saying the aftermarket rubber boot perished quickly 30 years ago (as seems to be the case today with the Yaris aftermarket lower control arm ball joint rubber boot).
The last posts include a quote from TCB for parts that include a replacement ball joint for the OE arm (or the Yaris aftermarket arm).

[Petrus]

I stand corrected.
TCB info suggests they cán be replaced.
So; whó dunnit?

[Joesson]

I stand corrected.
TCB info suggests they cán be replaced.
So; whó dunnit?

Here's a link that could be of interest to you:
https://www.spyderchat.com/threads/control-arm.152031/

[Petrus]

I stand corrected.
TCB info suggests they cán be replaced.
So; whó dunnit?

Here's a link that could be of interest to you:
https://www.spyderchat.com/threads/control-arm.152031/

Thank you; múch obliged.
He dunnit and says ´easy´ :-)

[Dev]

This was discussed in the thread ending here :
https://www.mr2roc.org/forum/index.php?msg=836158

I see that in #73 you mention you changed ´just the ball joint´.
Further on I read OEM DIY refurbishing too.
Also read Dev commenting that on some cars they cannot be removed.
Hmmm....
Just ´want´ to swap the ball joints and not get into a complex going for more expensive still project.

On some cars they are part of the arm. On our car it can be a serviceable part but some have had failures with its mounting clips.
I suppose it depends.

Those roll center ball joints correct the roll center from extreme lowering. I believe they were brought about for drifters and people that like to slam their car but I imagine they might have a race purpose for those that have radical set ups. For our cars its not necessary unless you go too low and screw up the geometry of the car making it handle much worse.  You have to consider that the spring rates will be effected and that is taken into consideration when they design a coilover system.
A little lowering is just fine without any major detrimental effects but once you go beyond a certain point there is a exponential drop off. 

These ball joints do the opposite of what the dog bones do.  The dog bones make the roll center worse going in the opposite direction.

[Petrus]

These ball joints do the opposite of what the dog bones do.  The dog bones make the roll center worse going in the opposite direction.

Yes, the dog bones are ´tuning´ the rear to match the lowered front. The Sportivo kit lowers the front more than the rear, creating rake.
This the front roll center drops more than the rear. The dog bones ´correct´ that mismatch to a degree.

I will go with the TRD rear arm braces first, then hopefully the Whiteline ARBs and thén, when I have set tose to my liking, máy ... whatever.
At the moment though confined within municipal borders with the ´touge´ fun this morning having proven a large step forward.

[Petrus]

Reading up on something else tripped over the specs of the Tein S lowering springs; 36 mm lower front, 31 rear. Sportivo spacers I´d say.

[Beachbum957]

Reading up on something else tripped over the specs of the Tein S lowering springs; 36 mm lower front, 31 rear. Sportivo spacers I´d say.

That is the spec, but on our MR2 with Tein-S springs, the drop was 1 3/4" front (44 mm), and about 1 5/8" in the rear (40 mm) with both KYB struts and Koni inserts. We have since raised the front about 1/4 inch with a thicker spring insulator at the top.

As for using dogbones, it also depends if you want to lower the rear inner mounts the to keep a near stock roll axis or allow a slightly higher rear roll center without them, which would give a slightly higher rear roll rate and a greater bias toward oversteer.  Since the spring rate increase from OEM with the Tein is greater in the front than rear, that has a bias toward understeer.  Add in the impact on camber gain when lowered because of the arm angles, and it is a bit more complicated than just correcting the roll axis.

Our solution for the street with the Tein springs was to use a stock front bar and remove the rear bar.  The handling is very predictable.  But this probably would not be the best solution for the track as it is biased toward understeer.

There are many ways to get similar results.  The goal is a combination that works and gives the feel and predictability that works for each driver.

[Petrus]

Suspension tuning is part art part science; part emperical part geometry.
You change óne thing, you change éverything and more so with McStruts front ánd rear.

With McStruts the larger the change the more compromised things get and 40mm is rather a lot. Yes, with 40 mm. the angles change markedly.
The spreadheet Adam28 gave is rather enlightening. Toyota knew a thing or two with not going a lot lower even with the TRD race springs.

The subframe spacer is ónly to tune the rear roll centre in the same direction as a lower front without lowering the rear.
In you case thus only without the spacer on the spring.

For mé the biggy is predictability.

As to the ARBs that remains an enigma for me:
Seems many people prefer lighter/no ARB rear which I get from traction pov. but less so because that is generally with OEM spring rate ratio front/rear, 100/150%.
TRD keeps them OEM stiffness ratio front/rear which I do not entirely get because they double the spring rate rear vs front whereas OEM is only 50% more.
Some, p.e. Spirit team goes a LÓT stiffer rear than front, taking a step further still in the above direction.
A bit large differences for personal preferences and not all explained by road/track either.
Glad I ordered adjustable ones ;-)