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springs for a 90 325is

Discussion in 'E30 (1984-1993)' started by ricco39, Dec 24, 2008.

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    I checked out the spring rate table off of e30tech.com and it gave two rates for stock E30 M3 springs: 114F/314R and 140F/250R. The first number came from the 6/87 issue of "Motor" (Magazine?), the second from who-knows-where. Those numbers don't mean too much unless we know if the drop is the same for both sets of numbers. Does anyone have any more information about rates or drops for stock M3 springs?

    BTW, the table says that the rates for H&R OE Sport and Sport springs are the same (180F/380R) but the Sport springs have a bigger drop. I suppose that the same rate with a shorter spring is what gives a firmer ride and better handling.

    cramartin guest

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    cabrio springs spreadsheet

    Great comments, guys. I'm building a spreadsheet with all these specs and comments, and I will publish it as it becomes mostly complete. Is there a way to post spreadsheets on bmwcca.org? If not, I'll make it public domain on google docs.
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    Huh? What do you mean? Do you know what a "spring rate" is? It is totally separate from the amount of 'drop'. You're concentrating on the static ride height and projecting that as more important than the actual spring rate. It is not. It is a completely separate issue.
    No ... I think you need to stop all this discussion about suspensions until you learn enough to know what each of these factors really means in terms of handling and ride quality. Your guesses aren't helping you or anyone else.

    cramartin guest

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    Mr. Hecht,

    Rather than shut down discussion and learning, would you like to please educate us suspension neophytes?


    cramartin guest

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    Correction, I meant to address this to Mr. Krieger. Thanks.
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    Did you wake up on the wrong side of the bed today? You might want to block any future posts I will be writing. I don't want to be responsible for causing you a stroke or a coronary. I have stated from the beginning on this forum that I am a neophyte and that I'm on a steep learning curve around automotive issues. It's clear from my posts that I am exploring these issues. If you don't have the patience to deal with that, please ignore me. As far as I know BMWCCA is for track stars and noobs.

    But back to the issue at hand. I wasn't saying that static ride height is more significant than spring rates, I was only trying to figure out their relationship. It only seemed logical to me that if you have two springs with the same rate and one has less height than the other then there will be a firmer ride (lower center of gravity). This seems to be the case with the H&R OE Sport and H&R Sport springs which have the same F/R rates according to the e30tech.com table I saw. But the Sport springs have a larger drop and are the firmer ride.

    I don't understand why you say that drop (i.e. height, length of springs, # of coils) has nothing to do with the spring rate.


    If the OE Sport has the same spring rate and more coils (less of a drop) than the Sport then I suppose that its wire diameter is decreased and/or the overall diameter is increased. If I'm missing something here I sure would like to find out what it is. Mr. Krieger, if you can't suppress your scorn for a pathetic ignoramus like me please take a pass. Thanks.

    Delphin25 guest

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    Stock 325i-----------------------106------------------------245
    Stock 325is----------------------118------------------------265
    Stock 325ix----------------------106------------------------308
    Stock M3-------------------------114------------------------314
    Stock M3--------------------------140------------------------250
    Dinan Sport-----------------------172------------------------300
    H&R OE Sport---------------------180------------------------380
    H&R Sport-------------------------180------------------------380
    H&R Sport (29664)---------------200------------------------285
    H&R Race-------------------------315------------------------ 570
    H&R Coilovers***----------------340------------------------380
    Eibach Pro-Kit--------------------102-------------------------277
    Eibach Race----------------------160-------------------------445
    IE SIII----------------------------315-------------------------570
    Koni Coilovers-------------------342-------------------------407
    Cosmo Coilovers----------------450-------------------------560
    TMS J-Stock**-------------------680------------------------1026
    FK 60/60 cup kit-----------------379--------------------------379
    Vogtland Standard***--------115/197-----------------------360
    Vogtland CS***---------------137/200-----------------------400

    Its the holy grail of E30 owners. tough choices but I cant even put into words the return.
    Ignore the buttheads. LOL Be patient.

    First Id go search
    r3vlimited (this list is from there, not complete GC will help you pick rates for coilovers)
    plus they have pics of E30's with different setup to see some ride hieghts wheel tire combos.
    then turnermotorsports, bimmerworld, groundcontrol, H&R, bilstein, ireland engineering
    elephant motorsports, flying brick, BMP, valley motorwerks

    my humble research opinions: ST bars 19.22mm, billy sports not HD, H&R Race not sports (most bang for the buck setup, NASA SPecE30 legal, not the fastest, but streetable, barely)
    BMP stress bar, (looks kool may help a bit, lol)
    GC coilovers, billy or H&R coilovers, Koni, Sachs, (coilovers are expensive but nice and adjustable)
    IE bars or H&R bars (not eibach)
    no eibach springs except with GC coiovers, not the conversion kit cant get good spring rates with it
    look at eibach numbers might as well go with springs off grandmas VW LOL
    no ST sport tech springs maybe speed tech
    no tokico, no KYB,

    PS: $125 to get tab supports welded. worth it.
    I installed rear bars on stock tabs, eventually broke one then got them welded.

    don stevens guest

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    Spring Shock Options

    Delphin 25's data amazes me.

    I have a Spec e30 so I know what the H&R race with Bilstein Sport combo feels like. I agree with him that it is streetable but it is very firm.

    I also have a convertible with Eibach Pro Kit springs and Tociko shocks. I have had the Eibach/KYB combo as well. Either combination is OK but not great (the front shocks are too weak).

    The Eibach springs are fine for the street and the give the car a nice posture. Notice the spring rates are essentially the same as stock, they are just shorter.

    I have a set of Bilstein sports in the garage that I simply have not gotten around to installing yet. From what I have read the Bilsetins should work well with the Eibach springs.

    What amazes me about the above data is the difference in spring rates between my Grandma Eibachs at 102/277 lb/in vs the H&R race 315/570. Having driven both on the track in my E30 (prior to converting it to race car) I would not guess the differences are that big.

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    Don't know why this thread got resurrected after a 4½-month slumber, but I have more time today and I can do a 'quick & dirty' summary if you haven't found this on your own ...

    I was not nasty; I was blunt and direct so you did not misunderstand.
    Your anomalous results are for exactly the reason I gave you in the first place. Spring rate is not related to spring height. You can make a very short spring with a very low rate if you wish. It would be kind of dumb to do that since it would make the suspension very easy to bottom out, but it can be done. You can also make a very high rate spring in stock length. It will ride like a buckboard and you'd hate it.
    OK; read that quote again. Where do you see any mention of spring length? It isn't there because it isn't a factor. You can make a 20-inch spring with a 200 lb/in rate and a 30-inch spring with the same rate. Putting a 200 lb load on either one will compress it one inch. Putting a 400 lb load on would compress it two inches. The only difference is the amount of weight you could ultimately put on the spring because the 20-inch spring will run out of compression room first.
    That is correct. However, because you run into the total suspension travel problem with a relatively low rate spring, nearly everyone* who makes shorter springs also makes them with a higher rate so the suspension does not bottom out. Now, remember the part about "active coils" affecting the rate? Here's how it works:

    When you take any spring and cut off some of the coils at the end, you wind up with fewer active coils. Part of the spring that was active is now 'dead' because it's against the bumper. The fewer coils left have a higher rate because there is less moving spring to take the same weight. If you have a spring with 10 active coils and a 200 lb/inch rate, each active coil will compress 1/10 inch under that 200 lb load. If you cut off enough to reduce the active coils by one, you then have a spring that will compress only .9 inches for the same 200 lb load. The effective rate is now 200 lb/0.9 in. or 222 lb/in. It can also help to understand this if you think of a leaf spring held at one end and free at the other. If it would deflect by one inch with a 200 lb load at the end, cutting off 10% of it and placing the same load would deflect it only 0.9 inches. Same thing happening, only in a coil.

    Now you should be able to see the reason we have to know both the length and the rate for replacement springs because they really are not related.
    Quit calling yourself names. I didn't.

    * Those who don't make springs that are very close to the same rate as stock. In combination with the rear set, these variances are used to tune understeer and oversteer characteristics. That's another Big Damn© lecture ...
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    CR, you just can't resist starting trouble, can you, in a 4.5-month-old thread, no less? :rolleyes:
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    Dude, look at the post dates. I didn't restart it. I just offered the answers they originally wanted. Tell the truth: That is a damn good explanation, isn't it? ;)

    z31maniac guest

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    I'm curious to see what my car is going to feel like with the new setup GC spec'd out for my swap and usage.

    550/750, with the 22mm UUC bar up front with spehrical end links and no rear bar.

    Hopefully the S52 swap will be up and running in the next week or two.

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