Suspension questions

JohnG7

Member
 Texas Gulf Coast- near Houston
Hello all,
Last year I purchased my Zed and I love it. Mine is a 2010 s30i auto (non sport) , I've always been partial to the N52, but honestly I do (at times) think about the 35i/35is instead (maybe one day). I did love driving at speed, but my racing days are behind me. This is my daily driver.

I have a few questions relating to tightening up the suspension just a bit. Mine is low mileage, @ 30k miles, I believe the front springs/shocks are too soft or struts weak). I rarely bottom out at speed, but still is pretty soft. I constantly bottom out as I leave my local grocery store. It doesn't appear to hurt anything, but I feel the suspension hitting the stops fairly abruptly. The 2 exits there are perfect for torturing my front bump stops, at any speed. Annoying at least.

My suspension is soon to see some change, yet I do not desire to stiffen it more than needed. I currently have run flats on the factory 17" wheels, may pick up a set of 18" wheels and non RF tires if I do decide to track it. Our roads vary widely in quality (many great, many not-so great), I fear I'd probably damage rims if I went 19". And, I read of rear spring problems that require replacement.

I wish I could say money was no object, but I can't. Yet, I do not wish to go halfway to getting it right. Was leaning toward just tossing a set of Bilstein B6 struts on her and be done, but that would allow the spring issue to bite me later (are the rear springs that fragile)? Looking at the Bilstein B12 pro kit that is in my acceptable price range, and would drop the car a bit. Living right on the gulf coast, driving a dropped car just doesn't feel smart when water is on the roads (I've mostly driven large pickups the last 45+ years of driving). Dropping the car by an inch really shouldn't hurt, I do pretty much park this car when flooding is local- but lately we flood streets often.

I have held back asking for advice while reading previous threads- I know others have asked these same type questions. I cannot find much on e89 suspension mods. I searched many bimmer boards and found lots of info on the M's, 2's, 3 's, etc and much will apply- not all. If anyone has links to good info that applies, I'd greatly appreciate being pointed in that direction.

I see the various coil over kits, and see prices start at affordable then go up. I find little to no feedback on the lower end kits (like the HR CO kit). Does anyone have experience with these they'd share? Has anyone here just installed a set of Bilstein B6/B8 struts and seen much improvement? Are the rear springs enough a problem that they should be changed as I replace the struts?

Again, I want to see improvement in damping to eliminate/lessen the front bottoming out mostly, lessening body roll would be great also- (but I really don't want teeth rattling stiffness). I would love to track this thing, but the 99% of time not tracking it is where I want to feel the springs. Like people everywhere, I must allow for our roads and potholes. Since the board is a little slow, I figured I'd toss this out there to see what I can learn. I promise I've searched and read all the zed4 areas I'm aware of. I'd appreciate any/all info you guys/gals have, I'd love to learn from others (mistakes and successes). A grand or so is my goal, but willing to raise this some if the benefit clearly outweighs cost. If anyone knows where to find relevant info, or who to ask, I'd be grateful. I really have looked for info, and found lots- just very little that helps in this case. I do most of my own wrenching, so any tips will help. And lastly, I believe all bushings are still solid, but am not opposed to swapping bushes or other parts if needed (altho shocks/struts take dibs). Thanks much.

Edited for grammer and mo' questions... (and this was the short version)...
 
Firstly Welcome and I apologies for my understanding on suspension.

Firstly do you want to track your car - as an track car needs different setup than a road car or daily driver (this is the section I currently preside in)

I decided to install KW'3 as I can change my setup for Daily Driver and Track day usage

Here is some insites - however its a cut and paste from another forum

Front tension struts:
Stock - soft bushings which will deflect under load
Upgrade - replace with ones from E9x M3 which have stiffer rubber bushings.
Effect - less deflection in front toe with a little more vibration transferred into the steering wheel. Will help reduce under steer.

Front wishbones:
Stock - soft bushings that will deflect
Upgrade - none currently as the headlight leveling rod is on the opposite side on the E89 and E9x. Still working on some possible solutions here

Front upper spring perch / guide plate:
Stock - no real "issue" other than stack height and lack of adjustment.
Upgrade - replace with ground control or Vorshlag camber plates.
Effect - camber and caster adjustment. lower stack height on the camber plate will give more travel in the strut when lowered

Front springs / struts:
Stock - no ride height adjustment. minimal adjustment to rebound possible (comfort vs sport mode)
Upgrade - fully adjustable coilovers or lowering springs
Effect - lower/adjustable ride height (also allows for corner weighting). adjustable compression and rebound can be made stiffer at the sacrifice of ride quality.

Front sway bar end links:
Stock - no real "issue" at stock ride height. Incorrect length when car is lowered causes geometry to be off.
Upgrade - adjustable sway bar end links
Effect - sway bar geometry restored so that frame mount and end of bar on same horizontal plane increasing effectiveness

Front sway bar:
Stock - a little on the soft side which can lead to under steer and limited roll control
Upgrade - replace with H&R 27mm sway bar
Effect - reduction in under steer, better roll control and turn in response

Rear lower wishbone:
Stock - no adjustment for camber, soft rubber inner bushing which can deflect under load
Upgrade - E46 adjustable rear camber arms with inner bushing replaced with rod end (solid mount)
Effect - large adjustment range for rear camber. slightly rougher ride with rod-end, but no deflection under load.

Rear trailing arm bushing:
Stock - lots of deflection under load will cause rear toe to change during hard corners
Upgrade - E46 rear trailing arm bushing limiters. These are just shims that are installed on both sides of the bushing greatly reducing deflection
Effect - rear toe maintained under hard cornering, no impact on ride quality

Rear trailing arm upper ball joint:
Stock - no issues, part used in E89 is the same as E46 M3 which is already fairly stiff
Upgrade - none

Rear trailing arm lower ball joint:
Stock - rubber bushing that will deflect under load
Upgrade - none. unfortunately BMW used a different size lower bushing in the E89, in the E85 and E46 this could be replaced with the better upper ball joint.

Rear upper wishbone inner ball joint:
Stock - rubber bushing that will deflect under load
Upgrade - Turner E46 monoball or Group N E46 bushing
Effect - Group N bushing uses stiffer rubber than stock will reduce deflection; Turner monoball replaces rubber bushing with a bearing that will not deflect.

Rear springs / shocks:
Stock - no ride height adjustment. minimal adjustment to rebound possible (comfort vs sport mode)
Upgrade - fully adjustable coilovers or lowering springs
Effect - lower/adjustable ride height (also allows for corner weighting). adjustable compression and rebound can be made stiffer at the sacrifice of ride quality.

Rear sway bar:
Stock - a little on the soft side which can lead to under steer and limited roll control
Upgrade - replace with H&R 21mm adjustable sway bar
Effect - increase in over steer, better roll control


Recommended stages

Stage 1:
- Stock struts/shocks (with adaptive suspension)
- Eibach or H&R lowering springs
- Front M3 tension struts 31102283575 / 31102283576
- Front adjustable sway bar end links
- Rear adjustable camber arms https://www.turnermotorsport.com/p-340474-rear-adjustable-camber-arms-pair-e36-e46-e85-turner-motorsport-streettrack/

Stage 2:
- Everything in Stage 1
- H&R front and rear sway bars
- rear trailing arm bushing limiter https://www.turnermotorsport.com/p-964-turner-motorsport-rear-trailing-arm-bushing-limiter-kit-rtab-shim-kit/
- rear upper wishbone inner ball joint replacement (Group N or Turner)

Stage 3:
- Everything in Stage 1 & 2
- Vorshlag or Ground Control front camber plates
- Fully adjustable coilovers
- rear subframe bushings (if available)


However the comon solution is Bilstine B12 or Elbach Pro Kit - both effective but these are cars that are not used on track
 
Many thanks for all that, I'll work on digesting it- all good info. I'm kinda bad about being unclear, I guess I should state my goals.
I would like to make my car one that is 99% road driven, yet (maybe) capable the 1% on a track or in track type use. Am at the stage of trying to not let the 1% dictate too much influence on the daily driving. My driving abilities are not that great and most likely will not improve. Diminishing returns too. I still could work towards stage one.

The car (as it is) handles better than this drivers ability to push it hard, and the 3.0 non-turbo motor would not be my choice for serious track use. I've owned a few cars with sports suspensions, I'm really not needing to set this car up for the track- as bad as I wish I could. I haul eggs more than ass anymore, am wanting to split the difference as much as possible.

I would be better served spending funds for improving my skills before setting this car up for the track. If I can improve it's agility and be able to still hit the occasional potholes without jarring my teeths I'm ahead of now. This thing impresses me as it is, but I feel me bottoming out happens too easy. I do not see anything showing damage and the shocks/struts still have some bounce- but I can do better.

I will file this info away and make sense of it all, much of it will come in handy. Right now, am leaning toward either the bottom of the C.O. kits, or the Bilstein spring/strut kits, these options are within the $1k range give or take. And since everything is a tradeoff for something. I would probably not justify much more expense for my uses. Were this car in my past, yes I would pursue stage 2 or maybe stage 3.

I read where people try this or that on the more populous BMWs, not so much on these. I do prefer to stay ahead of maintenance, without breaking the bank. Thanks much, I'll file it away. Is good food for thought.

I am in no big hurry, I'll start ordering whatever parts over the next couple months (probably nothing but summer here for a while). If anyone has experience with the Bilstein B12, Eibach, or similar struts/spring kits I'm listening.
 
i would try the sway bars first , see my other post , no downsides to ride quality , no reduced height issues
 
I was reading that thread and will definitely consider trying different sway bars, makes good sense. Would sway bars affect my bottoming out (when at slower speeds)? Either way I believe I would see benefit from slightly stiffer sway bars.

Maybe a set of lower coils along with new HD struts, and maybe a better sway bar at both ends make my list so far. The first reply covers the bases on all the options. If I was more able to track it, I would really benefit (but I'm not going that serious). I do desire this car to remain as a comfortable daily driver, yet maybe improve it's potential if pushed.
Almost everything I do ends up costing more than my initial plan, this is not un-expected. I do not mind spending the coin when it clearly makes things better.

I'll read up more on sway bars. More is better than less, but where is enough? :headbang: I'll read more...

reEDIT or UPDATE (06-13)--->> I HAVE READ EVERYTHING that I can find and even talked directly with enough people to now really be confused. I started originally thinking I'd be best served by something like the Bilstein B12 pro kit. But now, after reading many hundreds of pages of threads and manufacturers propaganda I believe I might best be served by something like the Bilstein B12 kit.

I was hoping someone had first hand experience with spring/strut changes on our E89. As much as I wish there was vast knowledge on these cars, I cannot find it when I look on my own. Many thanks to twin turbo and 35i-nut for their help, lots of great info. I do not wish to build mine into what it's potential holds, I see how these bush's and parts affect each other in use.

Thanks guys...
 
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