Complete Underside Refresh- Suspension, Steering, Arms, Subframes, Mounts...m50

[CMG]

CAR: 1989 BMW 325i Alpine Sedan w/ M50 & G260, and Z3 rack
PLAN: Complete suspension/steering refresh for a solid and fun daily driver (I don't mind a little stiffness and NVH). I have a ton of E30 and E36 parts already so goal is to use stuff I have or get best bang for the buck.
SWAY BARS: Currently car has stock 20/12mm. There are clearance issues sometimes with M50 but I'm gonna try to squeeze in either a stock 21mm oem bar or a 22mm ST front bar and 19mm rear bar (wtb 14.5mm oem rear sway bar)
SUSPENSION: Currently has Ground control basic coilover kit with adjustable spring inserts and blown Koni's. Checking to see about getting the Koni's rebuilt by GC.
STEERING: Car has Z3 steering rack. Which model do I use for replacement tie rods and ends?
BEARINGS: Gonna do all 4 corner 4 lug wheel bearing replacement. I think it's the front that you can only get bushings but the rear has cheap complete hubs and bushings for like $50 a pair so gonna give those a try.
SUBFRAMES/REAR TRAILING ARM: Absolutely everything is blown in the suspension, but all mounting points are good. I am local to Garagistic so I plan to use them to get replacement reinforced front and rear subframes and rear trailing arms. I will be using all their PU bushings which slide right in.
MOUNTS: Car currently has the E21 tranny mounts (they suck in my opinion, not a straight thru stud, one broke). Gonna use cup enforcers for that. Front mounts are E28 M5 with about 30mm spacers for M50 clearance.
HANDLING/PERFORMANCE: Currently car has stock E30 FCA and FSM, but it has revshift FCAB that are offset towards the outside of the car. For using standard E30 front strut housings, what is best FCA (e30/95 M3, or 96+ M3), best FCAB (centered or offset), and best FSM (stock or camber plates). With the goal being performance and handling.

[jeffnhiscars]

The front bearings come with the hub so you relpace the whole unit. Rear bearing are stand alone and for the effort involved in replacing them I'd stick with OEM which are typically FAG, SKF or Timken. Last one I bought was about $40

[CMG]

Yeah the rear bearing are under $40. I definitely need to do the rears for sure, I'll just repack the fronts if I can. There are cheap generic complete front hub pairs available for under $50, but the oem genuine ones are way more.
One question I had is about the front suspension. It uses the Z3 rack and oem strut housings w/ GC coilovers. I'm pretty sure the FCA are regular E30/96+ E36 ones, but the PO used revshift offset bushings, with them offset away from the middle of the car. For a moderately lowered E30 M50 car using the z3 rack and stock suspension what is the best combo for FCA and FCAB? Should I just use regular E30 FCA and centered FCAB, is there any benefit to just the offset FCAB?

[sklbase]

I have e30 FCA and offset FCAB. It gives you some camber to improve handling.


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[CMG]

I have e30 FCA and offset FCAB. It gives you some camber to improve handling.


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K thanks for the info. Right now the car is moderately lowered and visually looks to have negative camber and castor. I do like how it drives now, insane turning radius, and while light at high speed I wouldn't call it squirrelly. When using the z3 rack which tie rods and ends are the ones to use? Pretty sure they're all interchangeable but is there a difference between the e30 and e36 ones?

[CMG]

Another thing I was thinking about is the poly bushings. Off the top of my head I will need bushings for: rear subframe, lsd, tranny, rear trailing arms, etc. Since I will be using the garagistic stuff any bushing I use will be pretty much slide in. I'm tryin to check all the different manufacturers to see which are best for price and quality. There's garagistic, akg, and Ireland. Any recommendations. For some of my other cars Energy Suspension makes complete pnp bushing kits, wish they did stuff for bmw.

[jeffnhiscars]

K thanks for the info. Right now the car is moderately lowered and visually looks to have negative camber and castor. I do like how it drives now, insane turning radius, and while light at high speed I wouldn't call it squirrelly. When using the z3 rack which tie rods and ends are the ones to use? Pretty sure they're all interchangeable but is there a difference between the e30 and e36 ones?

You can use either but have to use the inner and outer from the same model as the threads are different. Keep in mind e36 tie rods are L&R. I've used e36 cause a) they are a bit beefier and b) they were less $$ when I bought them.

[CMG]

K, thanks for the info.

[CMG]

Finally getting to the point of getting this done. I'm going to try to keep it as simple as possible and use as much of the parts that I already have in hand. I had a couple of questions specific to the rear suspension. I am going to just drop the whole rear and do the subframe exchange with garagistic, and use poly trailing arm bushings. I had intended to use Turner Motorsport Delrin bushing for the LSD, and delrin tranny mounts too. The suspension is GC and has the solid GC rear strut mounts, and I am also using the IE rear sway bar mount reinforcements and rear strut bar. That pretty much leaves just the subframe bushings, and can't decide if I should do delrin or poly. I want the drivetrain to be stiff because due to M50 swap if that gets loose it can shove the engine into the radiator or cause clearance issues. I don't want the ride to be that firm, it's more of a daily driver than race car. Since I'm using Delrin LSD mount it would make sense to use delrin or solid subframe mounts, but really don't want to make the rear that stiff. Anybody ever used delrin diff mount with poly subframe bushings? Any insight into what might be a good combo for my needs?

[jeffnhiscars]

The only bushings that will allow engine movement are the engine and trans mounts. All the others you mention will only increase NVH at the expense of comfort.

[CMG]

Do you know that from experience? I have read lots of recommendations but having a hard time finding actual facts. Pretty much every company does say that the diff acts as a stressed member so basically diff and subframe bushings should be similar in hardness, so changed my mind and probably just gonna do poly diff and subframe bushings just to be safe.

[jeffnhiscars]

the only time I've ever seen an engine hit a radiator from a bad bushing is when the engine mount lets go. Beyond that you seem to have answered all your own questions

[CMG]

So, the end result of this thread was a full suspension refresh using oem bushings. I was really leaning towards using the garagistic exchange with poly bushings, the end cost would have been around the same price. In the end I decided to keep it stock because I didn't want to increase NVH, and I felt it would be better for long term resale value. I'm using GC coilovers and mounts, and front and rear strut bars, so that's stiff enough. Fresh bushings and ball joints makes the car ride like butter, and you can really feel the difference through corners.