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Thread: BC coilovers / spring rates

  1. #1
    Join Date
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    2007 Z4 M Coupe

    BC coilovers / spring rates

    Hey all,

    I am very interested in getting BC coilovers and could use your help with some info:
    1) Standard or extreme low version?
    2) Suggested spring rates?

    I am not looking to slam my car since it's my daily.

    Also, here are some measurements:
    Fender arch to wheels center cap = Front 16"; Rear 15"
    Gap from fender arch to the top of tire treads = Front 2 1/2"; Rear 1 3/4"
    Current: 2007 Z4 M Coupe (blue/black)
    Previous: 2001 740iL Sport (black/black), 2000 528i Sport (black/tan), 1995 318is (black/black), 1991 318is (white/black)

  2. #2
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    2001 740il
    I’ve had the standard drop bc on my il for 6 years no issues standard spring rate

  3. #3
    Join Date
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    Everett, WA, USA
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    '01 740i, '93 300ZX TT
    Standard 9k/6k spring rates (if I recall those correctly) but I would get extreme low. Extreme low at it's lowest would barely barely tuck the front tire. The standard would only get you ~1" lower than standard sport suspension and still leave you with wheel gap at it's lowest setting. The rear has plenty of adjustability on the standard set.
    To add, my settings are F10, R16 from the softest setting and everyone including my mom have never complained about ride quality.
    Last edited by PiotrC70; 03-11-2019 at 10:19 PM.

  4. #4
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    I got 1.5 in. Out of my standard height. which was perfect for daily driving

  5. #5
    Join Date
    May 2011
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    lA, ca, lA
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    BLK 01 sp, 20 Trail Boss
    I purchased the BC's with Swift springs but have not installed them as I got a Great Deal on some Bilstiein sports with H&R springs and at first didn't care for the stiffness but I liked the ride height and after a short time I decide I would just wait until these wore out then switch. The Swift spring is a bit softer and looks really cool most people I know think it's the best dollar for dollar deal on a quality coilover.......
    Last edited by setconstr; 03-23-2019 at 11:00 AM.

  6. #6
    Join Date
    Oct 2013
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    Louisa, VA
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    2007 Z4 M Coupe
    Thanks all for the input. I am trying to dig up more info about the drop rates between standard vs. extreme low, as most websites just talk about the general features.

    ECS Tuning has a little blurb but still not clear:
    1) Standard = "2 inch minimum and 3+ Inches of total potential drop"
    2) Extreme Low = "
    Extreme Drop version allows additional 1-1.5" lowering over the standard 2-4" lowering from traditional BR suspension kits" (so roughly 3-5" drop?)

    Since I want to get rid of my gaps (roughly F 3"/ R 2") and have a little extra wiggle room, based on ECS Tuning description, standard kit "should" fit my bill with the proclaimed 2-4" lowering. But,
    PiotrC70 says fronts are not low enough and still leave wheel gap.

    Also, are the standard 9k/6k spring rates great or would you up/down the rates, e.g. 10k/7k? I may consider the swift spring upgrade, which allow custom spring rates.
    Current: 2007 Z4 M Coupe (blue/black)
    Previous: 2001 740iL Sport (black/black), 2000 528i Sport (black/tan), 1995 318is (black/black), 1991 318is (white/black)

  7. #7
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    Sorry I don’t have a side shot on my phone, but here’s what standard drop bc coilovers look like. 1.5 front drop maybe 2 in. in rear. I set very little preload on springs and run 8-13 clicks front 11-15 rear on dampening. Ride quality is better than my m5 with lowtec springs and edc. This set up is perfect for daily driving, no scraping on speed bumps or dragging front or rear in driveways. Just my 2 cents.

  8. #8
    Join Date
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    Quote Originally Posted by Sundaycruzer View Post
    Sorry I don’t have a side shot on my phone, but here’s what standard drop bc coilovers look like. 1.5 front drop maybe 2 in. in rear.
    Sundaycruzer,
    My Bilstein B14s just asploded on me and I am considering standard BCs as a replacement. Is your car at the bottom of the range/middle/top? You look to be about where I have my 740iL on the B14/PSSes. I might be a little taller on the front. ( bad NJ/NY roads and such ).

    Between some of your posts, and others scattered on this and other forums, and I am not seeing any negative comments for the BCs for the e38. Thanks.

  9. #9
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    Quote Originally Posted by agentrnge View Post
    Sundaycruzer,
    Is your car at the bottom of the range/middle/top?
    ^ I would like to know that too. This info should give us some gauge about standard's potentials.

    From what I've read all over the place, these coils are great for e38/e39 community; and seem to be great in general.

    Here are other similar threads (maybe I should've bumped one of them ):

    https://www.bimmerforums.com/forum/s...ht=bc+coilover

    https://www.bimmerforums.com/forum/s...ht=bc+coilover


    PiotrC70, I saw that you had a dilemma with the fronts not being low enough, and that you had to get custom fronts, which makes me wonder if we should get a hybrid/custom set as well (e.g. extreme low front and standard rear).

    Also, my 2nd question is still standing: Are the standard 9k/6k spring rates great, or should they be upped/lowered?

    Current, stock suspension (gap has to go!):
    IMG_1530.jpg

    IMG_1780.jpg
    Current: 2007 Z4 M Coupe (blue/black)
    Previous: 2001 740iL Sport (black/black), 2000 528i Sport (black/tan), 1995 318is (black/black), 1991 318is (white/black)

  10. #10
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    To answer both questions, I had more adjustment to lower car more maybe another 1/2 to 3/4in. Maybe an in. lower or too max drop. When I first installed them I had them at max drop but for me, car was un drivable.

  11. #11
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    Here’s a better pic

  12. #12
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    2006 bmw 330xi
    Whats up everyone im new on here. I own a 2006 bmw 330xi and i recently just purchased BC extreme low coilovers. My front isnt low enough like i wanted to be. So is it ok if i leave the preload and spring alone and remove the bottom 2 locking collars and thread the strut body all the way up to the spring lock collar to get more low and that be used as a locking collar for that one collar??

  13. #13
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    Quote Originally Posted by Michael330xi View Post
    Whats up everyone im new on here. I own a 2006 bmw 330xi and i recently just purchased BC extreme low coilovers. My front isnt low enough like i wanted to be. So is it ok if i leave the preload and spring alone and remove the bottom 2 locking collars and thread the strut body all the way up to the spring lock collar to get more low and that be used as a locking collar for that one collar??
    I don’t recommend messing with spring preload that will destroy strut. I would try and leave at lest one lock collar or maybe see if you can put collar on the bottom of strut mount. I don’t think it would be smart to run without lock collar, but it’s your lose if it doesn’t work.

  14. #14
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    Quote Originally Posted by Sundaycruzer View Post
    I don’t recommend messing with spring preload that will destroy strut. I would try and leave at lest one lock collar or maybe see if you can put collar on the bottom of strut mount. I don’t think it would be smart to run without lock collar, but it’s your lose if it doesn’t work.
    Not messing with the preload at all the coilover has 3 locking collars. One collar to hold spring, another to lock that collar and another collar to lock strut. So basically jist saying remove the strut collar and the 2nd collar and leave the spring collar alone. Use actual strut housing to butt up againt the spring locking collar to lock the strut and spring collar. You know what i mean?

  15. #15
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    I've been interested in a mild drop to complement some 18" M Pars. How does the Sport springs with aftermarket shocks compare to a full blown BC coilover setup? Is there a significant difference?

  16. #16
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    Stock sport springs are about a 3/4" drop up front, but they're standard height in the rear. So not a massive drop. H&R Stage 1 is a little over a 1/2" lower than stock sport height all around.

  17. #17
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    BC coilovers / spring rates

    Quote Originally Posted by Michael330xi View Post
    Not messing with the preload at all the coilover has 3 locking collars. One collar to hold spring, another to lock that collar and another collar to lock strut. So basically jist saying remove the strut collar and the 2nd collar and leave the spring collar alone. Use actual strut housing to butt up againt the spring locking collar to lock the strut and spring collar. You know what i mean?
    Yes I do. Spring should have 2 lock collars and one on the strut mount. You could try it but the strut would eventually work itself loose I would think.
    Last edited by Sundaycruzer; 03-19-2019 at 09:36 AM.

  18. #18
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    Quote Originally Posted by rslifkin View Post
    Stock sport springs are about a 3/4" drop up front, but they're standard height in the rear. So not a massive drop. H&R Stage 1 is a little over a 1/2" lower than stock sport height all around.
    Thanks! How would you compare the ride between them?

  19. #19
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    I've only ever driven E38s with the stock sport springs, so I don't have a good comparison to the standard suspension or the H&Rs. The stock sport setup isn't super soft and cushy, but it's not harsh either. In my opinion, I'd say it's pleasantly firm but still appropriate for a big, comfy car. If you swap them in for lowering, swap the rears too even though they're the same height (they're a good bit stiffer than the standard springs).

    In terms of spring rate vs damper valving, the sport springs match up with the Bilstein HDs pretty well. Compared to stock sport shocks / struts I'd say the Bilsteins have a little more low speed compression damping and maybe a hair more low speed rebound, but they're otherwise pretty similar feeling. H&R stage 1 should work fine on the Bilsteins as well, from what H&R says they're only a little stiffer than stock sport springs.
    Last edited by rslifkin; 03-23-2019 at 10:18 AM.

  20. #20
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    Quote Originally Posted by Ruskii View Post
    ^ I would like to know that too. This info should give us some gauge about standard's potentials.

    From what I've read all over the place, these coils are great for e38/e39 community; and seem to be great in general.

    Here are other similar threads (maybe I should've bumped one of them ):

    https://www.bimmerforums.com/forum/s...ht=bc+coilover

    https://www.bimmerforums.com/forum/s...ht=bc+coilover


    PiotrC70, I saw that you had a dilemma with the fronts not being low enough, and that you had to get custom fronts, which makes me wonder if we should get a hybrid/custom set as well (e.g. extreme low front and standard rear).
    Yes, that's correct. If you look at one of my previous posts in the link below(hopefully the link works but if not, you can find it in the first link you posted)... my fronts are bottomed out/lowest setting with the custom fronts. Based on the pics I've seen, I sit about 1" lower than people with extremes bottomed out (again, only talking about the fronts here...)... At the time I purchased them years ago, BC tech support told me the extreme drop is about 1" lower than standard. I don't know if this has changed for the current kits but I sure as hell wouldn't go off of the ECS description claiming 2-3" drop on standards. The rears have WAY more adjustability and I can get my rears to really tuck but I don't like that look. As for spring rates, I'm perfectly happy with 9k/6k rates and use this car as a cruiser, not a sports car like some do. Even at their softest setting, it's still a tad stiffer than factory sport suspension. The car rides beautifully, absorbs & rebounds rough road great, and feels very planted.
    https://www.bimmerforums.com/forum/s...4#post29243084

  21. #21
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    Quote Originally Posted by rslifkin View Post
    I've only ever driven E38s with the stock sport springs, so I don't have a good comparison to the standard suspension or the H&Rs. The stock sport setup isn't super soft and cushy, but it's not harsh either. In my opinion, I'd say it's pleasantly firm but still appropriate for a big, comfy car. If you swap them in for lowering, swap the rears too even though they're the same height (they're a good bit stiffer than the standard springs).

    In terms of spring rate vs damper valving, the sport springs match up with the Bilstein HDs pretty well. Compared to stock sport shocks / struts I'd say the Bilsteins have a little more low speed compression damping and maybe a hair more low speed rebound, but they're otherwise pretty similar feeling. H&R stage 1 should work fine on the Bilsteins as well, from what H&R says they're only a little stiffer than stock sport springs.
    Super helpful post man. Thanks so much. After adding up Bilsteins with H&R springs (and a hardware refresh kit) it seems most sensible to just go for a set of mild coil overs and gain the adjustablity of that system.

  22. #22
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    Yeah, coilovers would give more adjustability, but I'm not sure if you'll gain any quality over the Bilsteins without spending a good bit more money. Bolt-in coilover options for the E38 are a little bit limited. Coilovers also do cost you a little bit of tire clearance to the inside, so depending on what you're running for a wheel / tire setup, that might be a concern.

    If camber adjustment is desired, you can get that without coilovers. Kmac makes camber plates for the E38, but I've heard mixed reviews. I've got a set of the Ground Control plates for an E39 M5 on my car (they bolt right in) and they've been good so far.
    Last edited by rslifkin; 03-24-2019 at 10:27 AM.

  23. #23
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    Go for extreme lows.
    I raised my car till stock to pass inspection, then back down.



    Lähetetty minun ONEPLUS A5010 laitteesta Tapatalkilla
    -E34 M60B40 + Tremec TKO 600 (sold)
    and sadly no old BMW anymore, only high powered Seat Leon Cupra 4Drive as a daily driver.

  24. #24
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    Nike32, I know that you sold your e38 pictured above, but do you recall the dampening settings you had (i.e. number of clicks from soft or hard?)
    Current: 2007 Z4 M Coupe (blue/black)
    Previous: 2001 740iL Sport (black/black), 2000 528i Sport (black/tan), 1995 318is (black/black), 1991 318is (white/black)

  25. #25
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    Quote Originally Posted by Ruskii View Post
    Nike32, I know that you sold your e38 pictured above, but do you recall the dampening settings you had (i.e. number of clicks from soft or hard?)
    Rear was half way, if I remember right something like 10-12 clicks starting from soft to hard.

    Front I was experimenting with Max hard, was just too bouncy, I tried with 50%, but then made it 100% soft, and it was in my opinion the best for me.

    Lähetetty minun ONEPLUS A5010 laitteesta Tapatalkilla
    -E34 M60B40 + Tremec TKO 600 (sold)
    and sadly no old BMW anymore, only high powered Seat Leon Cupra 4Drive as a daily driver.

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