I put paint lines on my eccentrics after alignments years ago and I've never seen them slip. I think the eccentric delete is useful for use with adjustable arms though to make side-to-side adjustments easier and eliminating the need for alignment when removing arms etc.
The rubber bushings definitely add a lot of deflection under load. They also add a lot of suspension stiffness which is why it's important to torque them at ride height. Eliminating these bushings and moving to M3 or aftermarket bits softens the rear suspension quite a bit. I remember when I had all the stock rear end components sitting in the driveway all the suspension arms stuck straight out. The weight of the spring, rotor, and caliper wasn't even enough to sag the arms from their static height. Those rubber bushings add I would guess 60-100lb/in of wheel rate and limits travel as they wind up. The rear sway bar was also bound by design which again added to the effective rear wheel rate.
Did the shaker rig testing more focus on strut/spring tuning? I've seen a VW report showing a base car vs a GTI and it broke down every bit of difference in ride height, camber change, and toe change throughout the suspension movements. The GTI cars actually performed much worse on paper due to their lowered ride height and worsened alignment changes. I can't find a link anymore. The GTI is still obviously the better handling car but that doesn't mean it doesn't make sacrifices to get there over the street trim car. Another interesting thing was that even with the ridiculously low spring rate they got from the factory the cars measured out to have over 1000lb/in of effective wheel rate. Probably similar story to above where control arms, sway bars, and bump stops added roll resistance. I am debating on moving up to stiffer spring for this reason as I have eliminated a lot of these things on my car. Makes me wonder how you came up with 7k/12k as a "track" (modified car) setup when that is basically the same rate( 6k/12k) that Ohlins uses for their regular r&t setup. So basically you are just revalving them? Doing the platform specific valving R&D for Ohlins that they should have already of done but instead they just use generic valving like everyone else?
After out last discussion I put a bit more though into my own aftermarket suspension setup. I like where it's at in terms of bump/droop distribution and ride height. Close to 55/45 strut travel distribution front and rear and 4.25" of ground clearance (ride height) with 6k/16k springs. However, I notice my control arms are oriented significantly different then a stock car which sits over an inch higher. I am also running the M3 rear end and M3 front control arms (longer camber arm). Front arms have reduced angle so I probably have less front steer than stock. I am thinking I could use a bit of bump steer correction up front. My rear arms are just about parallel to the ground at static height so I am guessing I actually experience toe-out when accelerating now and toe-in when braking into a corner. Rear toe-in under braking might be why the car is looser with the M3 components and lowered ride height. Static alignment changes might need to be made in the mean time. This is just guessed based on looking at the arms. Being multi-link maybe things aren't that simple though. I really need to measure all of this out. Just need to rig up some diy string alignment tools. I can foresee wanting to adjust some pickup points though eventually. Unfortunately, this level of tuning usually also puts you way out of class in competitive Motorsports... Straight to street mod in autocross for a basic bump steer kit lol.
Yes the rubber bushings do add a spring rate to the equation of the suspension. I have no idea what the rate is of all of them combined when measured at the wheel. Assuming all the rubber joints are torqued at ride height (IE no preload), 1 inch +/- of suspension travel at the wheel is very minimal rotation of the rubber meaning very minimal spring rate. But regardless, I agree 100% it does need to be accounted for although I've found the rear of BMWs to be less sensitive to spring changes than the front. In other words, I don't know that you would feel much of a difference in the car if all things stayed the same and bushing spring rate was removed.
As a side note... For those curious about poly bushings... This is why OEMs use rubber instead of Polyurethane. Friction is the enemy of suspensions and rubber doesn't have friction, only a spring rate (because the inner sleeve and outer sleeve are bonded). Since the inner and outer sleeve of Poly bushings are not bonded (because poly has poor elasticity) they have a fair amount of friction and to overcome that requires greasing them. This, of course, leads to self destruction as the grease traps dirt and turns it into sandpaper. If an OEM want's to reduce compliance in certain locations, they use ball joints which have minimal friction.
Shaker rig testing was damper/spring analysis. Anything beyond that such as body roll, etc requires hooking up the other "posts" of the shaker rig. Big $$. That's why I'm modeling everything.
I just want to first say that suspension tuning is a very subjective thing. Every car is different, every driver is different, everyone has their own opinions about NVH, the list goes on. What works for one person may not work for the other.
As for the spring rate, the Ohlins spring rates of the E9X 3 Series BMS-MI00 "regular" setup is 350 lbs/in front and 400 lbs/in rear which is 6.3k/7.1k respectively, not 6k/12k. I chose those rates based on a balance of streetability and track use, the added power of the 335i, and past experiences, observations, and testing.
As for the valving, Ohlins definitely does not use generic valving. Each kit has it's own specific valving. My only guess is development on the e9X 3 series kits was done on something like a 325i. There probably wasn't much squat when powering out of a turn with a 325i lol. Much like with any company, testing every variation of every make and model of every manufacturer would not be practical, nor the prediction of the upgrade path of each of those models and catering to that. When you look on paper at the difference between a 325i, 330i and 335i you are looking at ~215, ~260, and ~300 HP respectively. They probably decided its not worth the R&D time to distinguish suspension kits between the models with such minimal power differences. Add 100+ HP to the 335i and that starts to change things.
@Bnks334 when you say you are running the M3 rear end are you talking about the linkages, subframe, spindle or combination of them? The rear suspension is so hard to figure out because its hard to measure the deflection of the rubber bushings when loaded as you well know. Static measurement is one thing, what its actually doing under load is another and could be totally different than static.
As for the front camber/toe curve, I have the same M3 arms up front and am getting ready to measure the camber and toe curve so I can verify the modeling spits out similar numbers. I will definitely let you know what I find. Same with the rear.
lol.
