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Thread: E31 suspension rebuild illustrated

  1. #1
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    E31 suspension rebuild illustrated

    There's reason why E31 are priced around $6K on used car market. Restoring/rebuilding the thing is expensive. If you are looking for dealer/indy to do work for you prepare to pay about 3x more than price of the car.

    But if you DIY, it is fun and even a bit pleasure. I will not cover whole process, just most interesting places and places that by today will need attention on almost every car.

    I'll start with rear and cover ball joints, springs and struts.

    Parts needed:
    ball joints:




    more ball joints:



    wishbones



    enlarged part number:



    Also all new nuts for suspension. No pic.

    Here are parts to be replaced:



    Struts/Springs:



    Tools needed:

    BMW special toos/kits. Both are available from dealer ~$300 each. Takes about 2-3 months to deliver, my guess is they make them per request.
    Doing this job without those tools will be much more painful.






    Harbor freight kit:



    Press (optional),
    propane torch,



    impact wrench (if you want to make process easier),

    various tool grade bolts etc.






    Now the process. I had exhaust already removed from the car. Jack up rear arm, remove strut:










    Unbolt sway bar link. Unbolt cross member, lower jack remove spring:




    Then remove wish bone and cross member. Rest is pretty much - unbolt all suspension components that use ball joints. Remove brake rotors and hand brake assembly, otherwise you will not have clearance to get to lower ball joint.





    1st view on glory details:




    Removing ball joint from cross member is piece of cake:




    tool usage:


    After:



    Removing other ball joints requires right tools, and some fiddling torch heating and sweat:





    Here's why you need to remove hand brake assembly brake cable do not lets to place tool in place to remove lower ball joint.



    Later I used impact - much easier. Still need to heat up with torch:






    Inserting new ball joints is pretty much straight forward. Make sure you heat up parts and chill ball joints:




    Before putting things back, clean up your wheel arches:





    Here's finished side:





    Oleg.
    Last edited by perelet; 04-07-2012 at 11:52 PM.

  2. #2
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    Here are some observations about H&R springs and net rumors:

    Original rear spring vs H&R:



    Note H&H has one less coil.

    Spring wire diameter:








    According to basic physics H&R should be stiffer:

    Spring calculator

    Maybe I was "lucky" and got "right" H&R springs, but I'd call myth about H&R rear springs being weaker - BUSTED.


    For reference. Here's pic comparing rear Bilstein & original strut.




    Here's note about ball joints in wishbones. IMHO BMW is full of BS when they force you to buy new wishbones with ball joints. I pressed out ball joint out of wish bone - nothing special, same as in cross member, just different size. I'm sure by looking around one can find correct replacement part:













    Oleg.
    Last edited by perelet; 04-07-2012 at 06:57 PM.

  3. #3
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    thanks man, need to tackle the rear here shortly so this will come in handy for sure!

  4. #4
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    Ho Oleg,

    nice write up.
    I fully agree with you on what you say about BMW and the rear wishbones. So far I haven't been lucky in finding a plug&play ball joint as a replacement. I tried turning down an existing new spherical bearing to the 39mm outside diameter but the cage isn't thick enough. It just fell apart.
    So I'm actually taking an existing new joint, disassemble it in order to use the inner part of it and have the outer cage manufactured to my specs. Quite complicated and rather expensive but still only about 50% of the price of new OEM arms. And my arms are powder coated while BMW just paints them.

    Dust covers are mounted after the bearings are pressed in.
    Last edited by wokke; 04-08-2012 at 03:09 AM.



  5. #5
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    Thanks for that H&R spring comparison. I am not removing mines after all.

  6. #6
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    Nice write up and thanks for all the pictures. Job well done - much appreciated.
    "Adversity cause some men to break; others to break records." -William A. Ward

    "There" is no better a place than "here." When your "there" has become a "here", you will simply obtain another "there" that will again look better than "here."

  7. #7
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    Hopefully for under $50 you replaced the upper shock mounts.

  8. #8
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    Gotta love write-ups with lots of pics. Thanks for the effort Oleg!

    Tony

  9. #9
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    Maybe H&R has re-engineered their rear springs? A phone call would shed some light, if anyone is inclined. Here's the chart that MWrench put together a while ago:

    http://www.mwrench.com/Whitepapers/M...ing%20Dyno.pdf
    How come the middle half of any project always takes the most time?

  10. #10
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    Bill, disregard my e-mail from earlier... shop was talking about lower ball joints. They lifted the car and showed me what they were talking about, made a lot more sense than the initial "you need new spindles", lol.

    Thanks for the post Oleg! I too have to tackle the rear here soon.

  11. #11
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    Here's continuation - front suspension. I was lucky (or not?) dealer replaced front arms for previous owner, so I missed a bit of fun doing that. But I just redid front on my wifes E39 so I do not miss too much pressing out ball joints.

    Anyway here we go ...

    Front shocks come with new upper screw. Also bump stops sre build in,
    no need to order new ones.


    1st steps do with shock in the car - this will save a lot of wrestling on the floor.

    Lift rubber dust cover and pop up top cover. Noe you can loosen top mount (good luck with that). Do not unscrew it completely now - it will get really messy.


    Disconnect ABS sensor.


    Remove sway bar


    Loosen, but do not remove 3 mounting 19mm bolts on bottom of the strut. Jack up whole suspensoin few inches up.


    remove rotors and calipers


    I use impact to remove top bolt. Make sure your jack is secure. After bolt is removed lower jack slowly, hold strut and spring whole thing will pretty much lower down.


    Remove lower 3 bolts, holding the rest of the thing. Strut/spring will fall out


    Here's shock and spring.


    comparison of H&R and stock spring


    Wire diameter


    Carefully unscrew top nut, some oil will spray out, remove nut, remove factory strut,
    Drain the oil


    Clean wheel arches - mandatory


    Insert Bilstein, hand tighten new nut. You will tighten it up when strut is in the car


    Put jacj under suspension


    Put strut/spring dust cover, upper washer back, fit lower part, loosely screw old bolts,
    Guide top of the strut in hole. Jack whole thing up.


    Use o2 sesor wrench and hex bit to put right torque.


    I used new lower strut bolts and thread locking compound




    Suspension is in place.


    Oleg.
    Last edited by perelet; 04-21-2012 at 05:56 PM.

  12. #12
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    Thanks for showing those rear bushings! It's nice to see how those go in.

    However I must be the one to...

    Quote Originally Posted by perelet View Post
    Here are some observations about H&R springs and net rumors:

    According to basic physics H&R should be stiffer:

    Spring calculator

    Maybe I was "lucky" and got "right" H&R springs, but I'd call myth about H&R rear springs being weaker - BUSTED.
    They are not "net rumors." Numerous people have proven through either scientific testing or driving experience that the rear H&Rs are incorrectly sprung. People who end up removing them can't believe the difference it makes.

    Your smug and simplistic approach is the same mistake that H&R made when they designed them. The E31's suspension geometry is fairly complex. Forgetting to square a number or making the coils skinnier, even by less than a full millimeter can be a big deal. That small reduction in coil diameter is how they get the height drop out of them. Your "spring calculator" would work on most applications, but not this one.

    http://mwrench.com/Whitepapers/Mwren...ing%20Dyno.pdf

    http://mwrench.com/Whitepapers/Sprin...ear%202009.xls

    Auraraptor's E31 Suspension Sticky

    H&R Rears + Passenger = Dangerous


    I agree that too many times people base their opinions on forum-majority opinion and nothing else, but this is one of those things that has been objectively measured and recorded as well as road tested. Don't ignore the amount of effort and time that was spent researching and testing this phenomenon and just say "according to basic physics H&R should be stiffer" because they aren't...even though you are are correct in thinking that they should be.

  13. #13
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    Awesome post....thx for taking all those pics

  14. #14
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    Brilliant, informative post. Thanks for your efforts in sharing the process, makes the E31 slightly less enigmatic to non mechanically trained people like me. Makes me want to do my own

  15. #15
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    Thanks for the post. I have been struggling with how I was going to remove the old inserts. Your approach was extremely helpful. I was going to add bumpsteer spacers with the lowered front end. How does it drive with the new suspension?

  16. #16
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    How much are we talking for a full suspension overhaul? $2000? (in parts)

  17. #17
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    Informative and helpful post for the forum... Thanks

  18. #18
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    excellent illustration....I'm curious, why didn't you use the spacer plates from Phoenix motorsports?
    CB42366 - 1991 850i 6-speed. Brilliantrot & Black Nappa Leather
    CD00144 - 1994 850CSi. Hellrot & Black Nappa Leather


    My other projects:
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  19. #19
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    +1 :
    Quote Originally Posted by CaifanSC View Post
    excellent illustration....I'm curious, why didn't you use the spacer plates from Phoenix motorsports?
    (I need to get those things)

    And about the spring diameter, the H&Rs are narrower... wouldn't that make them softer, not stiffer?

    Oxford Green Metallic, Parchment leather, 854 badge, EDC stock struts, M-Sport springs, 3.91 LSD, CSI rear sway, 18" M-Pars, M-Sport wheel w/flappy paddles, CD-43 head unit, Strong Strut brace, Euro FTPs, CSI rear defuser
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  20. #20
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    Thanks for all the detailed photos perelet.

    I need to replace #2 bearings at both ends of the cross member (#1) and #23 bearings at the top of the wheel carrier (#22).







    No play yet, but just a matter of time with the seal compromised. Has anyone had experience replacing these bearings using something other than the factory tools? Don't mind buying tools, just not spending $300 for a tool that I will likely use once.

    It appears that these two bearings are unique to the E31.

  21. #21
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    I was the individual that originally announced in 2005, on Roadfly that the H&R rear springs was -17% weaker than the stock E-31 rear spring. The H&R rear spring dimensions I had were .0551 wire dia. x 3.8” coil dia. x 8.65 coils = 341 lbs/in”.
    That fact didn't go over very well at the time but this is a fact that has been independently confirmed numerous times.

    Unfortunately it is not a myth nor is an H&R springs with a 14.47mm (.562”) wire diameter stiffer than the stock rear springs.

    I’ve calculated tons of springs and adding +.010 to a spring wire diameter does very little to the spring rate!! It is also possible the +.010 could be contributed to a thicker paint. If it is actually a larger wire diameter the spring rate would still be only 370 lb/in and -10% weaker than the stock E-31 rear spring at 410 lbs/in.

    After disputing with every one I could reach at H&R, that their rear springs were 17% weaker than the stock E-31 and their less than willing to listen attitude, I personally had the H&R rear springs measures along side the stock 850, CSi and Dinan Stage-1 rear springs. All H&R did after I sent them the written results was to give me my money back!!

  22. #22
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    Quote Originally Posted by Mike in CT View Post
    Thanks for all the detailed photos perelet.

    I need to replace #2 bearings at both ends of the cross member (#1) and #23 bearings at the top of the wheel carrier (#22).

    No play yet, but just a matter of time with the seal compromised. Has anyone had experience replacing these bearings using something other than the factory tools? Don't mind buying tools, just not spending $300 for a tool that I will likely use once.

    It appears that these two bearings are unique to the E31.
    This will sound pretty low rent, but those spherical bearings will go on damn near forever if you inject some thick grease into what's left of the boots. You could even simply clean them up, squirt a shot of oil down into the interior, and then judiciously apply some bloogoo to seal them up again. Not primo practice, of course, but the point is that these things are ridiculously overbuilt and strong. After 200k miles they only loosen to the point that you can wobble the ball in the socket by hand a little easier, instead of real tight when new.

    You can grind down a cheap socket to press them with, on a press or with an acme thread. The threaded rod is easier; they're awkward to position on a press.
    How come the middle half of any project always takes the most time?

  23. #23
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    I actually did that with the grease Bill. Used a marine grease used for outboard motors that resists getting washed away.

    http://www.easternmarine.com/johnson...-grease-508298

    I had the cross member disconnected for removing springs, so I was able to work quite a bit into the bearing.

  24. #24
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    Quote Originally Posted by Mike in CT View Post
    Thanks for all the detailed photos perelet.

    ....
    No play yet, but just a matter of time with the seal compromised. ...

    Mike, mine were not worn badly - just a bit play, felt only after I removed them. But my car had that CSI with rear steering feel - fancy but felt weird. Rear had life on it's own and went where it wanted. I guess a bit of play makes for good change in rear toe in/out.

    Now after I put car together and aligned (with a correct toe in in front) I can feel what this car was meant to be - quiet and straight going at speed. No more that boat feeling. Honestly I have hard time understanding why people put laud exhaust on e31's. Get yourself 911 for that

    Quote Originally Posted by sctttoth View Post
    ... I was going to add bumpsteer spacers with the lowered front end. How does it drive with the new suspension?
    Scttoth, after putting car together and aligning I measured front camber - 0.7 deg that's even desirable amount of camber. With this amount no need to worry about bumpsteer. Bumpsteer is usually get's in play with hard A arm aka 911, 2 ball joint bmw front geometry does not need it at such small lowering.

    Rear suspension has about +- 1deg of camber adjustment, I set it 0.3deg.

    Oleg.
    Last edited by perelet; 04-26-2012 at 09:34 PM.

  25. #25
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    i was wondering if you have the pics available for this post? im rite in the middle of doing this exact same DIY'er and i'm looking for all the help i can get.....
    thanks!
    2011 LandRover RangeRover SC "White"
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    1991 BMW E31 850i M70

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