I Need Your Suspension Advice , Can You Help ??

[nrubenstein]

Unless you are running huge wheels with big roll center spacers, your roll center is way too low for the suspension to work right. There is no aftermarket suspension setup for an E30 that puts the front roll center above ground level. If your control arms are level or slope inward toward the oilpan, your roll center is below ground level and that is a bad thing. :down: No, cranking the preload on the spring way up does nothing because it doesn't increase the length of the strut from top hat to control arm, it just compresses the spring. The strut insert dictates the total length, and coil overs trade roll center and suspension travel for lower ride height and center of gravity.

I don't have a clue as to why manufacturers have done this other than to cater to the fan boy lowered car crowd. From my measurements you need about a 19 inch wheel (epic fail, too big, heavy and ugly) to clear big enough spacers between the control arm and the bottom of the strut to fix the issue (this is with GC race camber/caster plates. Stock non adjustable plates are about an inch taller, so that helps some, but still not enough, and you can't adjust the camber or caster enough)

I have H&R race springs, custom made 1.5" spacers that fit on top of modified GC race camber/caster plates to get things back to having the control arms level with the ground, but I still cant run the lower spacers with my stock 15 inch wheels. I'm not sure how much room I'll have with the 16 inch BBS RKs that arrived today. I have the UUC 22mm front bar and stock rear. I also have adjustable heim joint end links for the front.

Will

I haven't personally taken the measurement, but a friend of mine (who is a rocket engineer, and therefore understands precision) did some roll center measurements and calculated the roll center as 2" above ground at a ride height of 12.6" fender to wheel center.

Roll center correction matters. A lot. But you are way off base here.

Also, the point of the short stack camber plates is that they allow you to lower the car and retain suspension travel. In fact, with short stack camber plates and shortened struts, you may well gain travel, depending on your ride height choices.

[Paddlee30]

Can you enlighten me more on incorrect roll center and its effect on handling . Im no expert by no means and just beginning my journey in suspension knowledge/tuning. Thanks in advance !

[BlackbirdM3]

Unless you are running huge wheels with big roll center spacers, your roll center is way too low for the suspension to work right. There is no aftermarket suspension setup for an E30 that puts the front roll center above ground level. If your control arms are level or slope inward toward the oilpan, your roll center is below ground level and that is a bad thing. :down: No, cranking the preload on the spring way up does nothing because it doesn't increase the length of the strut from top hat to control arm, it just compresses the spring. The strut insert dictates the total length, and coil overs trade roll center and suspension travel for lower ride height and center of gravity.

I don't have a clue as to why manufacturers have done this other than to cater to the fan boy lowered car crowd. From my measurements you need about a 19 inch wheel (epic fail, too big, heavy and ugly) to clear big enough spacers between the control arm and the bottom of the strut to fix the issue (this is with GC race camber/caster plates. Stock non adjustable plates are about an inch taller, so that helps some, but still not enough, and you can't adjust the camber or caster enough)

I have H&R race springs, custom made 1.5" spacers that fit on top of modified GC race camber/caster plates to get things back to having the control arms level with the ground, but I still cant run the lower spacers with my stock 15 inch wheels. I'm not sure how much room I'll have with the 16 inch BBS RKs that arrived today. I have the UUC 22mm front bar and stock rear. I also have adjustable heim joint end links for the front.

Will

[6SPD]

I'm in for the info as well.

Shooting for the same suspension setup on my projekt when the coins come together.

[Paddlee30]

Forgot to mention its an E30 M3 .

[Paddlee30]

Thanks for viewing and for your advice , here is where im at with my suspension :

I have ordered the Ground Control Kit with the single adjustable Koni's , front spring rate 440 & rear is 650 . I now need to order a Sway Bar Kit and am having trouble deciding on what kit to get.
The main use for my car will be " Very Swift Mountain Runs" and occasional Auto Cross. Im NOT concerned with a harsh ride as this will not be my DD. I want to corner balance the car and know that a SB kit with adjustable end links is needed. As you guys know there are several SB kits out there in various sizes, please chime in with your opinion and why. Thanks in advance !!

Also on a side note , how will front and rear strut tower bars affect the handling after choosing a sway bar kit ?? I am planning on a S54 swap in the future .

H&R Front 22mm , Rear 18mm

Bimmerworld Front 22mm , Rear 19mm
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Suspension Technique Front 22mm ,Rear 19mm

UUC Swaybarbarian Front 22mm , Rear 19mm

IE Front 25mm , Rear 22mm

Eibach Front 19.5mm , Rear 16mm