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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > Roll Center?



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      02-04-2013, 04:53 PM   #1
pits200
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Roll Center?

Why do none of us e90/92 guys really ever talk about this. With lowering the car a few inches aren't we in need of addt'l suspension parts to bring the roll center back up?

With the control arms aiming up instead of level isn't this kind of offsetting the body roll we gain by lowering the car.

Anyone have some knowledge on this?
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      02-04-2013, 06:48 PM   #2
Techevo
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Yes, lowering the car will change the roll center and resistance to roll, but can be quite difficult to adjust correctly without inducing bump steer and changing roll centre balance.

I personally adjust spring rates, roll bars, geometry and ride height, then if I still have a problem with under steer or excessive roll, look at adjusting roll center. On my Evo 6, I manufactured my own lengthened ball joints to change front roll center, but eventually reverted to the standard setup due to upsetting the roll center balance (the rear was very difficult to adjust without major chassis changes)

Unless you're chasing fractions of a second on track or really enjoy developing your own parts like me, it's probably not worth it.


Last edited by Techevo; 02-04-2013 at 07:13 PM.
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      02-04-2013, 07:11 PM   #3
pits200
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I guess I ask because I feel I still have more sway than I'd like especially up front it feels like. I'm trying to learn but at least knowing that the roll center won't effect the car that drastically is good to know.
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      02-04-2013, 07:14 PM   #4
Techevo
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What spring rates and roll bars are you using?
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      02-04-2013, 07:22 PM   #5
pits200
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I'm an xi, ast coils, 426lb (somewhere around there)front springs and 672 rear. Rear m3 bushings, m3 rear bar, m3 strut brace.

Thats about it for my suspension mods. I'm sitting about 25.25 inches on all 4 corners with adjustable rear endlinks and waiting for the front adjustable endlinks.

I'm just unsure about drop height and the damper settings on my asts to find a happy balance. I'm about 6 clicks from soft in front and back.
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      02-04-2013, 08:11 PM   #6
Techevo
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Why the adjustable end links, do you plan on corner weighting?

What sort of balance do you have, mid corner, trailing throttle, and what is the adjustment range on the AST's?

Lastly, what tyres are you running and sizes?
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