I just could nót let it go. The Sportivo kit ´dog bones´ kept bugging me.
The problem is that the ´Rear Suspension Member Spacer t=3.2 Material: Steel Changing roll-centre position´
lówers the rear roll centre.
As such it does nót ´correct´ the 20 mm. lowering of the suspension.
Appearantly TRD thought it important so Í thought it important to try understand WHÝ??!!
I think I have unraveled the enigma: It is about balance.
1. Roll centre tuning is much more about the front and rear roll centers in correlation with eachother than their absolute positions.
2. The effect is instantanuous and irrespective of roll.
I will explain the latter. Anti roll bars and springs are action= - reaction: the more they are distorted the more they push against this distortion.
The roll centre is ALL about geometry: The effect is from zero.
Ok, now back to the kit.
The Sportivo kit firms up the front more than the rear. The front gets more responsive, gets more traction.
Now a step back again, sorry.
As with understeer/oversteer, more traction fron/rear does NOT mean the inverse at the other end. It is relative to the rear.
This is more easily understood with a tyre example: Going from 185 to 195 at the front gives a bit more traction. a bit less understeer. It does nót give less traction at the rear although the efféct is ´more´ oversteer. The brackets are essential: It is relative.
We all know that our Spyder is very sensitive to changes in balance.
We have seen that roll centre tuning is ALL about balance.
Now, with the Sportivo kit, TRD lowers the front and rear the same.
It adds a relatively stiffer front arb though. This is connecting left and rear wheels with a stiffer torsion spring. Compressing one wheel will see the spring pushing the other wheel down with the same force.
Although not without down side, it overal keeps more front rubber on the tarmac; increases front traction thus responsiveness. It relatively! gives relatively more oversteer etc.
By slightly changing the roll centre balance towards more decline at the rear, the traction at the rear increases. It does in effect the same as a stiffer arb at the rear, without the down side and waht´s more from zero.
What the spacers do is;
(https://i1.wp.com/suspensionsecrets.co.uk/wp-content/uploads/2018/06/macphereson-rc.jpg?w=750&ssl=1)
(https://i.ibb.co/X75TqFv/rollcenterspacer.png)
lower the chassis attachement of the lower suspension side = lower the roll centre. It is easy to see that it is geometry. That it works at any position at any speed.
So, there we have it. The spacers in the Sportivo kit make the rear relatively more stable, will improve throttle control.
Now bear with me a bit more.
This álso applies to other stiffening of the front like by mounting a front strut brace!!
A front brace adds a support between the two McPherson struts. Forces on the one are supported on the other.
Not the same as an arb but it does give more traction at the front. More responsiveness, less understeer = réatively more oversteer.
And now we get to the fire cracker: Imo the spacers are also beneficial when ónly a front strut brace is mounted. It restores the balance without the down side of stiffening springs/arb.
Me digging this up was triggered by stateside questioning TRD´s wisdom.
Boris (Snelbaard) has sold very few.
Now, it does work.
If you have a front strut brace then PÍNG!
I say get them while they are availeble; they are easy to fit, cheap, work and roll centre tuning is quite trick. They are the dog´s ... bones :))
Fascinating stuff.
Can follow it and understand it. Could not explain it back.
Quote from: Ardent on May 9, 2020, 09:50Fascinating stuff.
Can follow it and understand it. Could not explain it back.
Simples: Have a front strut brace? Do the spacer too.
Why: To maintain traction balance.
Says I and you know how I am about bolt óns....
Thats my take away.
As i do not have any additional bracing.
Nothing for me to do.
Quote from: Ardent on May 9, 2020, 11:41Thats my take away.
As i do not have any additional bracing.
Nothing for me to do.
Spot on.
Interesting. Wonder how that applies to my setup.
TRD being based on a stock MR2 with stock wheel/tyre sizes and stock struts, camber etc.
If all of that is different, do they still make a difference? Or has the balance been counteracted already somewhere else..
Quote from: shnazzle on May 9, 2020, 13:27Interesting. Wonder how that applies to my setup.
TRD being based on a stock MR2 with stock wheel/tyre sizes and stock struts, camber etc.
If all of that is different, do they still make a difference? Or has the balance been counteracted already somewhere else..
Go back to the TRD Sportivo kit.
The kit consists of several elements which do different things ánd TRD also had most availeble as a seprate set too:
Coil overs with lowering springs, balanced front rear as set.
ARBs front rear, balanced as set.
Imo you can thus take them out of the equasion concering front strut brace and/or subframe spacers.
So, the front strut brace and the subframe spacers. Imo balanced as set.
Now if you would firm up only the rear arb a whiff, that would also match the front strut brace but with the down sides of a stiffer arb.
The odd thing is that they only provided the spacers with the complete kit, not when the brace was sold seprately.
I thínk that is because the Sportivo set was to be non plus ultra and beefing up the rear arb even more has downsides. Thus they came up with this.
Why so much focus on these little unobtrusive, when mounted invisible even, spacers? Well, becaúse they are. Why would TRD come up with them, include them in the kit whereas it is the one and ony non-bling part of the kit?
Imo it is glaringly obvious that Toyota thought them important.
I thínk I have worked out why.
Back to your question.
If you have your mods balanced to achieve what you want, including balancing the effect of the strut brace, then it is superfluous.
This takes into account that you may have prefered chánging the balance. I myself p.e. have more air in the front tyres because I prefer a whiff less initial understeer.
Lastly there is a difference in balance between the pre face lift and face lift models.
Bottom line is you may or may not want to match what the strut brace does.
A neat explanation of what the TRD Sportivo subframe spacers do; as per TRD info ´correct roll centre´:
http://speed.academy/suspension-tuning-how-to/2/
got the right size bar - making them for when the subframe goes back on - great read by the way
Quote from: tets on October 28, 2020, 19:56got the right size bar - making them for when the subframe goes back on - great read by the way
Boris (Snelbaard) had them on the shelf. Thanks.
Quote from: Petrus on October 28, 2020, 19:38A neat explanation of what the TRD Sportivo subframe spacers do; as per TRD info ´correct roll centre´:
http://speed.academy/suspension-tuning-how-to/2/
I've got roll centre correcting ball joints in storage somewhere.
Will fit one day.
Quote from: 1979scotte on October 28, 2020, 20:16I've got roll centre correcting ball joints in storage somewhere.
Will fit one day.
Where did you get them from?
Looked around on the web and find them a bit costly.
Quote from: Petrus on October 28, 2020, 20:27Quote from: 1979scotte on October 28, 2020, 20:16I've got roll centre correcting ball joints in storage somewhere.
Will fit one day.
Where did you get them from?
Looked around on the web and find them a bit costly.
Gt4 play I think had them years.
Made by hard race.
MR2Ben is the only one at the moment. Indeed HardRace. His price is in line internationally. Just think it costly. Will think about it but probably bite that bullet.
Why have you not fitted them yet?
Quote from: Petrus on October 28, 2020, 21:07MR2Ben is the only one at the moment. Indeed HardRace. His price is in line internationally. Just think it costly. Will think about it but probably bite that bullet.
Why have you not fitted them yet?
Because I'm on my 3rd mr2 and still own 2 and always have other mods to do.
Was told it was a great handling mod buy somebody who had them fitted seems to be rare.
Stupink it was I think.
Quote from: 1979scotte on October 28, 2020, 21:39Was told it was a great handling mod buy somebody who had them fitted seems to be rare.
Stupink it was I think.
I totally get the need; it is simple geometry.
About nobody fitting them I am not that surprised as it is not cheap yet not visible. I do think it a bit odd if dedicated racers did not fit them.
Quote from: Petrus on October 28, 2020, 20:12Quote from: tets on October 28, 2020, 19:56got the right size bar - making them for when the subframe goes back on - great read by the way
Boris (Snelbaard) had them on the shelf. Thanks.
I know but I have the correct size bar so drilling 2 holes and cutting to length is easier!
Quote from: tets on October 28, 2020, 22:01I know but I have the correct size bar so drilling 2 holes and cutting to length is easier!
Ok.
Hello,
I wonder how thick the bones are and why not just take some washers instead ?
Going to replace my rear subframe over winter and I intend to give it a try.
BR
Ralf
they are 3mm thick. Washers could also be used but I wanted to make as exact a replica of the TRD items as I could, so I did :)
Quote from: 1979scotte on October 28, 2020, 21:39Quote from: Petrus on October 28, 2020, 21:07MR2Ben is the only one at the moment. Indeed HardRace. His price is in line internationally. Just think it costly. Will think about it but probably bite that bullet.
Why have you not fitted them yet?
Because I'm on my 3rd mr2 and still own 2 and always have other mods to do.
Was told it was a great handling mod buy somebody who had them fitted seems to be rare.
Stupink it was I think.
Ah, the ball joints are not a replaceble item?! Need to fit a replacement lower arm assy? How does thát work?! You´d still need to fit the after market ball joints! If that is possible on say a Yaris arm, how come the OEM ball joints cannot be swapped?
Quote from: Petrus on October 29, 2020, 18:00Quote from: 1979scotte on October 28, 2020, 21:39Quote from: Petrus on October 28, 2020, 21:07MR2Ben is the only one at the moment. Indeed HardRace. His price is in line internationally. Just think it costly. Will think about it but probably bite that bullet.
Why have you not fitted them yet?
Because I'm on my 3rd mr2 and still own 2 and always have other mods to do.
Was told it was a great handling mod buy somebody who had them fitted seems to be rare.
Stupink it was I think.
Ah, the ball joints are not a replaceble item?! Need to fit a replacement lower arm assy? How does thát work?! You´d still need to fit the after market ball joints! If that is possible on say a Yaris arm, how come the OEM ball joints cannot be swapped?
This was discussed in the thread ending here :
https://www.mr2roc.org/forum/index.php?msg=836158
Quote from: Joesson on October 29, 2020, 19:17This 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.
Hope you're not asking me not got a clue
Quote from: 1979scotte on October 29, 2020, 20:08Hope you're not asking me not got a clue
Ok, send me yours and I´ll try for free :-))
Quote from: Petrus on October 29, 2020, 20:05Quote from: Joesson on October 29, 2020, 19:17This 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).
I stand corrected.
TCB info suggests they cán be replaced.
So; whó dunnit?
Quote from: Petrus on October 29, 2020, 20:35I 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/
Quote from: Joesson on October 29, 2020, 20:53Quote from: Petrus on October 29, 2020, 20:35I 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´ :-)
Quote from: Petrus on October 29, 2020, 20:05Quote from: Joesson on October 29, 2020, 19:17This 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.
Quote from: Dev on October 29, 2020, 21:14These 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.
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.
Quote from: Petrus on November 1, 2020, 21:08Reading 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.
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 ;-)