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Thread: Supplied BC coilovers 6kg/mm spring rate, too soft for track e30m30?

  1. #1
    Join Date
    Nov 2009
    Location
    Brisbane, Australia
    Posts
    1,076

    Supplied BC coilovers 6kg/mm spring rate, too soft for track e30m30?

    Given the extra weight in the front of my car due to the M30B35 it *might* not be ideally sprung right now and after some google searches of rates and conversion tables it seems I have the 6kg/mm (315lb) springs all around where it seems that a far heavier 550lb ish spring seems preferable for your track day e30 rear end with the 315lb retained for the front.

    Springs are cheap, I'm willing to do some trial and error to achieve that go kart handling I so desire.

    So which way do I go??

    How long IS a piece of string?

    Someone has already told me I could comfortably double my spring rates they are so low, but his point of reference is a solid rear axle datsun 1200 race car he helped set up and an extensive Honda background so I'm looking for BMW based opinions.

    Simon Harrex of RX automotive has already told me an e30m30 will turn but has stated that spring rates are critical to set up, but he's too shrewd to give up his trade secrets when I could be paying him to set the car up for me (and I'll learn nothing).

  2. #2
    Join Date
    Nov 2007
    Location
    melbourne
    Posts
    2,238
    i would have thought thats quite low for the front.
    I run 12kg up front and 8 or 10 in the rear

    Depends how well the damper can control the spring.

    You are right 60mm ID Eibach springs are about 200 a pair.

  3. #3
    Join Date
    Oct 2005
    Location
    Melbourne
    Posts
    5,772
    What's the car doing where it's not handling properly.

    Understeer?
    No traction out of corners?

    What's your alignment spec u run on the track?

    What tyres are you running?
    1974 2002 M10, dogleg 2307cc
    1984 E24 M635csi M88/3 dogleg
    1987 E23 735i M30 auto
    1994 E34 540i M60 6spd supercharged
    1997 E36 M3 S50B32 supercharged (U/C)

  4. #4
    Join Date
    Jan 2013
    Location
    Sydney
    Posts
    3,150
    for track work you'd step up the stiffness a bit 6kg is more street oriented weighting

    The reason the e30 is supposed to use a stiffer rear spring is because of your horse kart suspension, the semi trailing arm horse kartness applies more angular mass on the spring, than say if you have a true coilover acting in the rear.

    there are a lot of factors when determining spring rates tho. Ideally you design spring stiffness to minimise or delete sway bars, but if you're not going to pay for the engineering for that than go stiff, 10/12's or 8/10's and use sway bar and alignment to fine tune the suspension.

    Burkey you run a true coilover at the rear don't you?

    I think you need to keep in mind are you actually a good enough driver to take advantage of the suspension tweaks that pro drivers use to gain 1/10ths of seconds, or will you even be able to push the car hard enough where any flaws are that obvious, do you expect you'll even know how to tell what suspension flaws are holding the car back?

    I say this because realistically if you went with a say stock standard 6/8 setup that was properly corner balanced and have the camber/caster/ toe setup by someone knowing what they're doing I think'd you be pretty damn happy with the handling
    E36 3182025M3iS aka "Bitsa" S50B32 - UUC Corsa Exhaust - Wilwood 332X 32 front rotors w/ Wilwood SL's Hawk HT10 Pads - TMS Braided Lines - DGR Coilovers - TMS rear camber arms - -4 FR -2.5 RR - Carbon Fiber Sunroof - Momo mod78 - AGI Half Cage - Road and Race Corner Balance (1160kg) - M3R/ LTW Front Splitter - STW Rear Spoiler - Hard/ STW Center Lock 18X8.5 on 245 Nitto NT01's - 3.91 1.5 way LSD

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