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      08-25-2021, 05:49 PM   #67
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Quote:
Originally Posted by tlrid3r View Post
I have invested a bit of time and effort to create this for myself. Rear axle roll center correction and bump steer like schirmer cars. This is 16mm of roll center correction. This is the kinetics schirmer speaks of. I took inspiration of what is current available, but create my own design, CAD and measurements.
It can be done. I'll be testing it out soon.
More info to come.
This is awesome - really interested in seeing how this turns out. Run the strom uprights in the front as well and would love an accessible solution for the rear. Keep us posted!

Last edited by OG Shark; 08-25-2021 at 07:05 PM..
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      08-25-2021, 08:13 PM   #68
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tlrid3r I'm excited to see what you can do at Laguna after some testing!

Looks great! Do you know how much roll center correction is required for 10mm below competition package? I'm guessing that's 20mm from factory height if you were talking the standard height.
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      08-25-2021, 09:53 PM   #69
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Quote:
Originally Posted by derbo View Post
tlrid3r I'm excited to see what you can do at Laguna after some testing!

Looks great! Do you know how much roll center correction is required for 10mm below competition package? I'm guessing that's 20mm from factory height if you were talking the standard height.
Correct. Comp pack plus 10mm below is about 20mm. From my measurements going positive on roll center correction doesn't have a negative affect. But just because I said 16mm of roll center correction that # means very little. Its the amount offset allowed with in the oem subframe mount hard points. The real # that will make an affect is the amount of degree change the arm gains. At 25mm lowered you are back at oem roll center. Lowered further than 25mm you start to lose a bit of roll center correction. Less than 25mm lowered you are positive on roll center correction. Might be better but I haven't tested.
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      08-26-2021, 11:05 PM   #70
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Quote:
Originally Posted by tlrid3r View Post
Correct. Comp pack plus 10mm below is about 20mm. From my measurements going positive on roll center correction doesn't have a negative affect. But just because I said 16mm of roll center correction that # means very little. Its the amount offset allowed with in the oem subframe mount hard points. The real # that will make an affect is the amount of degree change the arm gains. At 25mm lowered you are back at oem roll center. Lowered further than 25mm you start to lose a bit of roll center correction. Less than 25mm lowered you are positive on roll center correction. Might be better but I haven't tested.
That's pretty neat. I do wonder without front roll center correction, this seems moot to my car.

You are making me regret not getting in on that Strom group buy now..haha
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      08-27-2021, 12:33 PM   #71
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Quote:
Originally Posted by derbo View Post
Quote:
Originally Posted by tlrid3r View Post
Correct. Comp pack plus 10mm below is about 20mm. From my measurements going positive on roll center correction doesn't have a negative affect. But just because I said 16mm of roll center correction that # means very little. Its the amount offset allowed with in the oem subframe mount hard points. The real # that will make an affect is the amount of degree change the arm gains. At 25mm lowered you are back at oem roll center. Lowered further than 25mm you start to lose a bit of roll center correction. Less than 25mm lowered you are positive on roll center correction. Might be better but I haven't tested.
That's pretty neat. I do wonder without front roll center correction, this seems moot to my car.

You are making me regret not getting in on that Strom group buy now..haha
I bought the Strom upright mostly cause I'm a sucker for machined aluminum parts and it's something outside of my capability. Plus it's also helps with mounting 295-305 tire clearance upfront. The rear you can already do that. You can fix front roll center with two control arm from SPL. Easy and cheaper.
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      08-27-2021, 03:15 PM   #72
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Quote:
Originally Posted by tlrid3r View Post
I bought the Strom upright mostly cause I'm a sucker for machined aluminum parts and it's something outside of my capability. Plus it's also helps with mounting 295-305 tire clearance upfront. The rear you can already do that. You can fix front roll center with two control arm from SPL. Easy and cheaper.
mounting the 295/30/18 up front sounds like a good benefit too.

Do you plan to make a few extra sets of your rear sphericals?
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      08-27-2021, 04:05 PM   #73
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Could also move the subframe up a bit with these (12mm of correction for extra $):

http://www.mk-motorsportteile.de/epages/63717011.mobile/en_GB/?ObjectPath=/Shops/63717011/Products/%22Alu%20Lager%20e92%22



Quote:
Originally Posted by tlrid3r View Post
Im not a expert, just an engineer with an interest and looking for a solution to our platform. It's not just about being lowered or not. It's that lowering exacerbates this negative affect exponentially. Because it all adds up. Loading into a corner, riding the berms all impact roll center when you most demand it.
High spring rates can help but the car may be great a one track and not the other. Because proper suspension articulation is what provide mechanical grip. But the word articulation is not use to say that more movement is better.
Simply put, if your car is lowered and your roll center is in the proper place. The moment arm with have a less leverage on moving the chassis, your 600lbs spring may be sufficient where your would need 1000lbs spring with improper roll center.
Than to add on top of that. Camber loss, bump steering due too improper motion. Roll Center correction should fix all that.

My design and from what I can see from the limitation of the rear subframe (with-out major modifications of cutting into the subframe) all other providers of roll center correction kit can only correct a max of a 25mm drop from factory height.
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      08-27-2021, 04:55 PM   #74
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Ha! I have the BW subframe bushings installed on my car, they dont correct for roll center that I am aware of. It doesnt make sense to me that moving the subframe away from the car corrects geometery as that would further make it worse. Moving it up as the car is lowered makes more sense to correct geometery.


Quote:
Originally Posted by SAMM3Y View Post
Interesting you just shared these as I was pondering this last night while talking to some other m3 dudes about about roll center correction. These bush actually divorce the subframe from the chassis not move it closer. The BimmerWorld bush do the same thing.
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      08-27-2021, 05:08 PM   #75
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Quote:
Originally Posted by M43S7RO View Post
Ha! I have the BW subframe bushings installed on my car, they dont correct for roll center that I am aware of. It doesnt make sense to me that moving the subframe away from the car corrects geometery as that would further make it worse. Moving it up as the car is lowered makes more sense to correct geometery.


Quote:
Originally Posted by SAMM3Y View Post
Interesting you just shared these as I was pondering this last night while talking to some other m3 dudes about about roll center correction. These bush actually divorce the subframe from the chassis not move it closer. The BimmerWorld bush do the same thing.
I do too and I'm trying to figure out why, when they're installed from the bottom up all the way to the flange, they move the subframe away from the car. Looks like that link you posted though the rc correction is +100euro. So does that include the offset bush for the lower control arms?
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      08-27-2021, 10:35 PM   #76
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Quote:
Originally Posted by derbo View Post
mounting the 295/30/18 up front sounds like a good benefit too.

Do you plan to make a few extra sets of your rear sphericals?

I can, but I paid a big penny for these. Mainly because the low quantity run with the machine shop. I purchased all the spherical bearings at full price, I didn't get any discount. Only thing I regret is having the bushing black anodized, they get scratched with a press fit install, I would do clear anodizing, plus it cost less. I didn't cheap out on anything. I also did several 3D printed parts to check fitment and design which also cost a lot. In all I spent $3100. I would have to do at least enough for 10 cars to be able to bring the cost down. I think the cost has to be cut to at least half or else just buy Schirmer or MK parts. I think we need a group-buy to be set up.

Also a little update, I finished the complete install, I got to drive the car to my work to use a lift so I can do a string alignment. It feels more hooked, I feel like I have more grip, my street wheels have 275 square PS4S, I hope it's not placebo. I will soon do a track test, but it has just been too hot here in California, plus all the fires are not so pleasant. My track wheel runs 295 square AR1's. Here is a little video of the suspension motion and where the control arms end up at ride height with my Hubstands that I also made. They are perfectly horizontal from pivot point to pivot point.

FullSizeRender

Bonus picture (In home HubStand setup)
Only way I can properly do suspension development at ride height and get proper measurements.
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Last edited by tlrid3r; 02-22-2024 at 12:13 PM..
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      08-27-2021, 10:40 PM   #77
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Quote:
Originally Posted by M43S7RO View Post
Could also move the subframe up a bit with these (12mm of correction for extra $):

http://www.mk-motorsportteile.de/epa...Lager%20e92%22
I heard form someone here on the forums that you need to cut and weld to install this one because you need to create clearance for the subframe or it hits the body.
but I can't find any real info on that.
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      08-28-2021, 12:36 AM   #78
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Quote:
Originally Posted by tlrid3r View Post
I can, but I paid a big penny for these. Mainly because the low quantity run with the machine shop. I purchased all the spherical bearings at full price, I didn't get any discount. Only thing I regret is having the bushing black anodized, they get scratched with a press fit install, I would do clear anodizing, plus it cost less. I didn't cheap out on anything. I also did several 3D printed parts to check fitment and design which also cost a lot. In all I spent $3100. I would have to do at least enough for 10 cars to be able to bring the cost down. I think the cost has to be cut to at least half or else just buy Schirmer or MK parts. I think we need a group-buy to be set up.

Also a little update, I finished the complete install, I got to drive the car to my work to use a lift so I can do a string alignment. It feels more hooked, I feel like I have more grip, my street wheels have 275 square PS4S, I hope it's not placebo. I will soon do a track test, but it has just been too hot here in California, plus all the fires are not so pleasant. My track wheel runs 295 square AR1's. Here is a little video of the suspension motion and where the control arms end up at ride height with my Hubstands that I also made. They are perfectly horizontal from pivot point to pivot point.



Bonus picture (In home HubStand setup)
Only way I can properly do suspension development at ride height and get proper measurements.
Unfortunately, I dont see a video but the pics look great! The cost of curiosity. It definitely sounds like it makes more sense to just buy the MK bushings. I'm not sure what kind of group buy interest there would be or who would be willing to facilitate one.
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      08-28-2021, 01:28 AM   #79
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@derbo

I'll gather more details and finish my testing. Than I can look into group buy. Again I think if there is enough people it's possible to bring the price down to maybe $1400 to $1500. Maybe even cheaper. MK bushing is $1850 mainly because international ship. Schirmer is $2400+
Only reason I didn't just buy one those is because I working on other development stuff for my car.

https://flic.kr/p/2mjApct
Not sure if this works. If not I'll fix it tomorrow
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      08-28-2021, 01:59 AM   #80
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Quote:
Originally Posted by tlrid3r View Post
@derbo

I'll gather more details and finish my testing. Than I can look into group buy. Again I think if there is enough people it's possible to bring the price down to maybe $1400 to $1500. Maybe even cheaper. MK bushing is $1850 mainly because international ship. Schirmer is $2400+
Only reason I didn't just buy one those is because I working on other development stuff for my car.

https://flic.kr/p/2mjApct
Not sure if this works. If not I'll fix it tomorrow
That video works! Shipping internationally from Europe definitely is costly.
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      08-28-2021, 10:10 AM   #81
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Quote:
Originally Posted by tlrid3r View Post
@derbo

I'll gather more details and finish my testing. Than I can look into group buy. Again I think if there is enough people it's possible to bring the price down to maybe $1400 to $1500. Maybe even cheaper. MK bushing is $1850 mainly because international ship. Schirmer is $2400+
Only reason I didn't just buy one those is because I working on other development stuff for my car.

https://flic.kr/p/2mjApct
Not sure if this works. If not I'll fix it tomorrow
Loving what you are doing! Do you mind sharing what ride height you are currently at? Like the standard bmw measurement bottom of rim to fender lip (with the wheel diameter), or hub center to fender lip measurements.

Trying to balance your feedback of the roll correction amount you have achieved against the ride height changes you have made.
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      08-28-2021, 10:24 AM   #82
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Quote:
Originally Posted by Biginboca View Post
Quote:
Originally Posted by tlrid3r View Post
@derbo

I'll gather more details and finish my testing. Than I can look into group buy. Again I think if there is enough people it's possible to bring the price down to maybe $1400 to $1500. Maybe even cheaper. MK bushing is $1850 mainly because international ship. Schirmer is $2400+
Only reason I didn't just buy one those is because I working on other development stuff for my car.

https://flic.kr/p/2mjApct
Not sure if this works. If not I'll fix it tomorrow
Loving what you are doing! Do you mind sharing what ride height you are currently at? Like the standard bmw measurement bottom of rim to fender lip (with the wheel diameter), or hub center to fender lip measurements.

Trying to balance your feedback of the roll correction amount you have achieved against the ride height changes you have made.
Sure no problem. My current ride height.

18" wheel
Front 580mm
Rear 564mm
This is measured from bottom of rim lip to fender edge.
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      08-28-2021, 10:54 AM   #83
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I just got the fall line LCA. It comes with a camber shim set. Does this help with roll center correction, or does it need to be in the bushing?
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      08-28-2021, 11:33 AM   #84
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Quote:
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I just got the fall line LCA. It comes with a camber shim set. Does this help with roll center correction, or does it need to be in the bushing?
The shims just help lock adjustments into place from what I know. The bushings are needed to change the geometry of the suspension itself.
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      08-28-2021, 11:38 AM   #85
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Quote:
Originally Posted by roastbeef View Post
I just got the fall line LCA. It comes with a camber shim set. Does this help with roll center correction, or does it need to be in the bushing?
Nope. The arm pivot points need to be moved up or down in order to change roll center.
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      08-28-2021, 12:22 PM   #86
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Quote:
Originally Posted by derbo View Post
Quote:
Originally Posted by roastbeef View Post
I just got the fall line LCA. It comes with a camber shim set. Does this help with roll center correction, or does it need to be in the bushing?
Nope. The arm pivot points need to be moved up or down in order to change roll center.
Quote:
Originally Posted by roastbeef View Post
I just got the fall line LCA. It comes with a camber shim set. Does this help with roll center correction, or does it need to be in the bushing?
Quote:
Originally Posted by derbo View Post
Quote:
Originally Posted by roastbeef View Post
I just got the fall line LCA. It comes with a camber shim set. Does this help with roll center correction, or does it need to be in the bushing?
Nope. The arm pivot points need to be moved up or down in order to change roll center.
Yup it does not. That adjustment shim is for camber setting.

derbo is correct.
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      08-28-2021, 05:49 PM   #87
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Great accomplishment, and I look forward to the results on the track! From what I see, you did correction on the camber link. Did you consider correction on the rest of the arms? If not, why? Thanks.
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      08-28-2021, 10:06 PM   #88
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Great accomplishment, and I look forward to the results on the track! From what I see, you did correction on the camber link. Did you consider correction on the rest of the arms? If not, why? Thanks.
I did the correction also on the trailing arm a total of 8 bushings. The Trailing arm corrects bump steer.

2 eccentric bushing with spherical bearing internals for Camber arm (Roll Center correction)
2 eccentric bushing with spherical bearing internals for trailing arm (bump steer correction)

Per side of the car.
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