Added a fairly complete tech article on tires, did some editing, and added a link to Turner’s excellent spacer guide.
Table of Contents:
I Introduction
II Both Axles
Shocks/Struts
Springs
Coilovers
Wheel Bearings
Sway Bars (Anti-Roll Bars)
III Front Axle
Front Axle Diagram/Overview
Control Arms
Lower/Front Control Arm Bushing (LCAB/FCAB)
Strut Mounts
Tie Rods
IV Rear Axle
Rear Axle Diagram/Overview
Rear Trailing Arm Bushings (RTAB)
Trailing Arm Bushings
Camber Arm/Rear Lower Control Arm
Subframe/Differential Bushings
Rear Shock Mounts (RSM)
V Suspension Kits
VI Technical Discussions
The Tire as a Critical Suspension Component
Helpful Links
Spacers Guide
E36 M3 Alignment Guide
__________________________________________________
I – Introduction:
This FAQ was designed for anybody interested in E36 suspension.
Organization is by axle. Each specific item contains a description, and BMW OE part numbers. Some components also include a failure mode description. Note that only major components are covered. Small bolts, nuts, and interconnecting pieces are not referenced. I suggest www.realoem.com for locating specific things.
I use the word OBD1 M3 to describe the 1995 US model year M3 with the S50B30 engine. OBD2 M3 to describe 1996-1999 US model year M3s with the S52B32 engine. 3-Series to describe 328, 325, 323, 318 i, si, ic, and ti cars with M50, M52, and M4x series engines. This guide is focused on US spec cars, although much of this information no doubt applies to the world market as well. Also perhaps, but not necessarily, applicable to the E36-based Z3 Roadster and Coupe
Yeah man, fantastic job… I will definitely be referencing this thread when I have a suspension issue.
Incredible write up. Thank you for posting this.
Nice work, this should make for a good start for people. One question, do you know who does reasonably priced Bilstein revalving?
Wow! Very well done, sir.
A+ thread!
thank you im done with my suspension but this is really going to help the community.
did you type all of this up?
A+ write up!
thanks a lot!
now if we can teach people to search
Cheers folks. Put it to good use. If you see anything incorrect, any points I did not make, grammatical errors, things you would like to see added, anything at all… let me know.
Yes I did, result of too many "wtf do I do about my suspension?" threads. I’m just going to drop this link into every one I see… and the "I got a new BMW" threads… et cetera. I encourage everybody else to do the same. Figured people might actually pay attention if I used diagrams with pretty colours. When I’m satisfied with its accuracy and completeness I may make a request to have it stickied in some form or another.
PM’d you.
This is a thread-in-progress. I will continue to update, fine tune, and collate data and images on the matter. Goals at the moment:
- What exactly is different about forward control arms between all models? Bushing density, replaceability, and geometrical differences. As well as the true advantages of each.
- The actual geometrical advantage posed by the M3 forward swaybar design and any inherent disadvantages it may have (I have seen folks hint that there are a few).
- Clarify the diagrams somewhat. They are my composites using realoem.com diagrams as a base point.
- Provide an image of each main OEM piece, and if possible explain what primary failure modes they exhibit, how to detect failure, and why these failures happen.
- Determine if there is a shortage of grease in OE wheel bearings, and if so how to pull them apart and pack them for proper life.
- Some sort of more comprehensive aftermarket parts listing for each component.
- Links to and perhaps reformatting and compiling of DIYs on these topics.
NOTE: If anybody wants to donate server space I can turn this into a website instead (more navigation and organization options).
At some point in the future I may compile other topics in this way… most likely starting with brakes or the cooling system.
WTG, this is a really good effort. So talk to us more about valving shocks, since you identify that as being so critical. Like if I call up Bilstein and tell them that I have an E36 with H&R springs, will they pop some nonstandard valves into their shocks for me?
My 95 has the original shocks under it. I am considering what to put on it. I don’t plan on racing the car, but I do want something comfortable and handles the road well. I was considering the stage 2 kit from pelican, do any of you have it?
Because I do not dabble in valving shocks intimately (just racing the results), I’m better off letting this thread explain it to you: http://forums.bimmerforums.com/forum…=981161&page=2
Know that I have ridden on custom valved shocks side-to-side with the factory valved variants (all other things being equal) and the difference is simply alarming. It took a few experiences with different shocks, springrates, and vehicles but I am an absolute believer in correct valving. If you think about it though, most everything logically falls into place once shock valving is the central issue.
The shock is what governs the wheel’s reaction to the road. If you hit a bump, yes the spring compresses, but more than that the impact forces the shock to absorb the bump at a rate which will keep the tire in contact with the surface. Then push it back down at a rate that not only maintains does not ‘bounce’ or unsettle the vehicle and still maintains tire contact. There is low, medium, and high speed rebound and compression occurring in a shock (and perhaps more than that). Various speeds of piston movement result in different reactions.
The geometry (bushings, control arms, trailing arms, ball joints, mounts) controls the alignment and articulation of the tire. The spring separates the sprung and unsprung masses with a flexible yet transmissive layer. The shock is responsible for keeping the tire attached to the road.
Why does the H&R Sport behave like crap with Bilstein Sports, but much more civilized with Konis? Well… mid-speed rebound and damping (the part of the shock response that most actively controls the spring) are so different between them. Why are coilovers so much smoother despite having identical spring rates to many individual spring sets? It’s due to the fact that they are factory valved to work well with the springs they ship with. Why can you drive a very harsh spring setup (700/800) and still have the car be relatively tolerable, yet another car with much softer springs (320/400) feels like it’s crashing into every bump? A properly valved shock can control the spring’s reaction, thus maintaining the suppleness of the ride and tire contact.
I will see if I can’t get a better dissertation on this in the future. From somebody that knows more than me ideally. I do not believe Bilstein (or any other shock company for that matter) will custom-valve you a shock set, unfortunately. I wish they would.
Wow, thank you for making this thread. Being pretty new to this I learned a lot. The diagrams were a great touch. I look forward to reading more of your right ups.
Why does the H&R Sport behave like crap with Bilstein Sports, but much more civilized with Konis?
I was getting ready to purchase the H&R sport springs and the Bilstein sport shocks for my 95 325i vert but now I am re-thinking this based upon your post (well-written by the way) and this particularly quoted comment.
Could you enlighten me just a bit more about this combination? I am a pretty regular reader of these posts but have not really heard about this. Thanks very much
Well primarily I was speaking of the E36 M3 variant of the Bilstein Sport. For some unknown reason Bilstein seems to have gotten the valving on that shock completely wrong and it is, no other word for it, dreadful.
The standard 3-Series Bilstein Sport setup is nowhere near as bad, to the best of my knowledge it is valved in a relatively pleasing way. Konis do tend to provide a more comfortable ride than Bilsteins with factory valving and are adjustable (if you feel like getting technical).
I would pull the trigger on the H&R/Bilstein combo so long as you stay with the shocks designed for the 325/328. Just fyi there is an ongoing Bilstein group buy that has the best prices I’ve seen. Tire Rack tends to have good prices on H&R Springs.
It is weird that most people haven’t heard of the concept of shock valving. Actually off-road guys are pretty hip to it and have been doing it for years. I’m sort of confused why it hasn’t trickled down to the performance car enthusiast yet in a big way.
Cheers.
Awesome, thanks for making the contribution
Good thread. Thanks for putting it together.
Doug
Lovely thread.
Bumping this thread due to substantial content changes. Here are the hilights:
- Roughly twice the information as the last version.
- Post has been restructured, moved to an external editor, and fully spellchecked (apologies for misspellings previously).
- More detailed information on a variety of components (front control arms, spring hats, etc…).
- Table of Contents added (when your post needs a table of contents, you need to get a life )
- Most everything has been re-worded in the interest of objectivity, accuracy, and brevity.
- Added motion ratios for those of you really serious about suspension calculations.
- Better layout to all component entries providing a description of what it is, where it attaches, and often how it fails.
As always, if anything is not to your liking feel free to contact me about it.
Very well done Spoonman! You’ve done a great job here. Thanks for the link in the Definitive Alignment thread, these subjects go hand in hand.
Years ago (on DTM Power IIRC) there was a table of spring rates of the popular aftermarket spring choices for E36, if you could find that I think it would be helpful.
Also, I wonder if actually giving advice about some of the tried and true E36 Coilover systems (Koni/GC, PSS9s, ASTs, etc) may be helpful to reduce the question…"how are xyz coilovers".
From my experience, Koni SA shocks and struts have comfortable compression damping on the street, and perform well up to about 500-550# spring rates. I just switched to the PSS9 kit (dampers only using GC coils), and the compression is noticeably stiffer, but they can control significantly higher spring rates, which where Im creeping toward. Also, I know there are fundamental differences between twin tube and monotube (monotube have higher gas pressures, and less hysteresis), but I don’t know enough about the differences to be really knowledgeable. Maybe you can shed some light on that too.
Also, maybe you are willing to go into suspension theory of the E36 chassis. I don’t know if anyone has yet explained the concept of keeping the front end stiff with lots of static neg camber, and running the rear softer to allow for a nice dynamic camber curve. Also, the concept of tuning with sway bars, spring rates, and shock damping. You think those things are realistic to tackle?
Oh yeah, this should be stickied in the new Suspension Forum! (….and the Alignment Guide )
+1 on stickied. Awesome very informative thread.
That would be handy advice, as well as a more detailed explanation on springs, spring rates, and what they do. I’ll use the all-powerful Google and see what can be dug up. Vorshlag is also attempting to compile a list as well it seems… everybody send them your used OE springs! http://www.vorshlag.com/tech_springrates.php
I am actually currently in the process of compiling just such a list. From DDM to Motion. Part of the aftermarket compilation (along with bushings, swaybars, et cetera…). Trying to pick up rides in as many different sort of individual setups as I can… I hate just regurgitating information without verifying it myself.
Thanks for the review. Yes… I am currently facing the same problem of simply not understanding more than the fairly simply basics of shock valving. I know a couple guys who can explain a bit more though, I might see if I can have them chime in. Or explain it down to my level.
Definitely is possible. I have included a section for just such more in-depth dissertation (technical discussions), I will add it to my list of things to write. The guide is trying to cater to the novice user as well as the sophisticated and intermediate user. Being able to separate initial purchase maintenance questions from coilover corner balancing questions is important (and a function of organization, not content sophistication).
Cheers!
One thing I’m confused about is the two mentions of Trailing Arm Bushings related to the rear axle. One is mentioned as RTAB, and one merely "Rear Trailing Arm Bushing". Should I change both?
On another note, I wanted to change my front LCABs and so I ordered 33-32-1-136-311, but that’s actually something completely different! eEuroparts.com lists it as "trailing arm bushing (lower)" for the rear! Instead I need 31-12-9-059-288 for my front LCABs.
So now I need to figure out what the hell I need to do my RTABs. Do I need 33-32-6-770-786? eEuroparts.com list that as "Trailing Arm Bushing (upper)" for the rear.
The other thing I ordered — 33-32-1-097-009 — I have no idea what it’s for! Rogue Engineering show it as the 1995 E36 RTAB.
Wow great write up, this should come in handy this summer when I do my suspension overhaul.