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  • wheelrate/springrate ratio

    Does anybody have any information regarding how E30 M3 rear trailing arms affect the wheelrate/springrate ratio? Do the rear wheels truly see the 900 lb/in of the spring?

    I assume the front control arms keep a 1/1 ratio.

    Im just trying to take everything into account before I order my set of K W variant 2 coilovers

  • #2
    Uhh.. Thats a sweet kit you're concidering.

    I've got a KW on mine and it works great.

    I think my model is: Competition with adjustable bound and rebound
    in addition to height adjustment front and rear.

    I don't know the rear springrate, but i think i'm running 140N up front
    Steffen Otto Jensen
    จจจจจจจจจจจจจจจจจจจจจ
    1989 318is
    1989 M3 Cecotto (196/505)
    www.cecotto.dk

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    • #3
      by the way have a look at this:
      http://www.e30m3performance.com/tech...e/eff_rate.htm

      It might be helpfull
      Steffen Otto Jensen
      จจจจจจจจจจจจจจจจจจจจจ
      1989 318is
      1989 M3 Cecotto (196/505)
      www.cecotto.dk

      Comment


      • #4
        As per Gustave's website, the conversion factors (motion ratios) are 0.88 for the front and 0.45 for the rear.

        A stock E30 M3's springs are

        Front 140 lbs/inch * .88 = 123 lbs/inch wheel rate
        Rear 250 lbs/inch * .45 = 112 lbs/inch wheel rate

        So, the front/rear wheel rate mirrors the weight distribution, about 52/48%.

        Your 900 lbs/inch rear spring would be 405 lbs/inch at the wheel.

        Hope this rambling helped!

        Anders
        Anders

        "Objects in mirror are losing..."

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        • #5
          so If I'm running 600lb rear springs in the rear, that means I have only 270lbs at the wheels. Is this too soft?

          what are the stock rates?

          Karl Kraus --Education is a crutch with which the foolish attack the wise to prove that
          they are not idiots.

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          • #6
            As I stated above, stock spring rates are 140 Front / 250 Rear. You're running 2.4 times stiffer than stock...

            Anders
            Anders

            "Objects in mirror are losing..."

            Comment


            • #7
              it seems one would then want to get springs in rates where the front/rear wheelrates would be kept in a ratio mirroring weight distribution.

              its too bad I dont have access to a set of scales. I really dont know where the longitudinal center of gravity is in my car. assuming 50/50 is optimal, I could just select springrates conforming to this ratio, and worry about getting the weight distribution right later. It shouldnt be tough to get right, there are so many ways of gaining/reducing weight front and rear.

              However, is 50/50 really optimal? would a further rear bias not be better? I was thinking higher loaded fronts during braking and entering, therefor more grip up front, would be better than having that more load on the rears during application of throttle on exit. yes, you do want to be focused more on exit speed than entrance, but i question whether the rear tires of even a highly tuned s14 powered e30 m3 are highly strained at the rpm ranges the motor would be spinning during the first bit of throttle application upon exit.

              i surely dont know what im talking about, i can hypothesize, but thats all it is. can anyone chime in?

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