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Planning the evolution of my j-stock car

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  • Planning the evolution of my j-stock car

    So I've been basically driving my old j-stock car as is for ages. Other than losing about 50-60 pounds by taking out the A/C and carpet and misc interior bits, it's still on the same TMS j-stock suspension it had when I bought it in 2006.

    It's back at VSR for an engine rebuild, and I'm figuring out where to take it from here.

    I'm likely to get some more power from the rebuild (from cams + engine management, and am thinking about trying to take some more weight out (sunroof delete, possibly a CF hood).

    My goals:
    - make it a bit more streetable
    - give up as little track capability as possible
    - keep the cost of the build somewhat reasonable
    - prefer not to make one-way modifications to struts, etc

    I've generally been happy with the j-stock suspension; I'm not racing competitively anymore, and for instructing and track days it's been great. That said, it's pretty harsh on the street and it's not adjustable at all.

    Questions:
    1) does anyone have any real world track experience with the new KW V3 suspension? Any comparison to the j-stock suspension?
    2) how well will the j-stock suspension do with a <2600lb car?
    3) am I missing other options or ideas?

    thanks in advance!
    Seattle, WA
    currently:
    1988 M3 ex j-stock
    1984 911 RoW 3.2
    http://cars.g93.net

  • #2
    I'd also be curious to know how the KW's or other options are for a car at that weight.

    As I've lightened my car over the years I find the J-stock suspension too stiff for anything but very smooth tracks. It's especially noticeable in braking zones, or if I grab a bit too much curb and get tossed. I've adjusted my driving to slide the car more, since it wants to sit so flat, and have to run tires that don't mind that. In the rain it can be downright sketchy, even with no rear bar.

    It's been on my short list to replace it for about 7 years and I just haven't gotten to it.

    Comment


    • #3
      Originally posted by Mick View Post
      I'd also be curious to know how the KW's or other options are for a car at that weight.
      Probably depends a lot on spring rate.

      BTW - Both the KW V1 and the V3 versions for the M3 are in stock at Bimmerworld.

      BMW E30 M3 Coil Over Kit - KW Variant 1 (bimmerworld.com)

      BMW E30 M3 Coil Over Kit - KW Variant 3 (bimmerworld.com)
      1990 M3

      Usually it's best not to know how much money you have into your M3

      Comment


      • #4
        Originally posted by mwagner10702 View Post

        Probably depends a lot on spring rate.

        BTW - Both the KW V1 and the V3 versions for the M3 are in stock at Bimmerworld.

        BMW E30 M3 Coil Over Kit - KW Variant 1 (bimmerworld.com)

        BMW E30 M3 Coil Over Kit - KW Variant 3 (bimmerworld.com)
        I don't think they stock them but they can certainly order them for you.


        E30M3 is a Legend

        Comment


        • #5
          Yeah, I’m sure I can get them; what I’m less sure about is what they actually are. I’ve called Bimmerworld to ask about spring rates for the V3, and the only answers I get are ‘mumble mumble proprietary mumble ‘not published’’ etc. I don’t think they know either.

          KW makes a clubsport variant for other chassis that’s suppsedly stiffer, but not for the E30.

          If anyone has any real world experience with the KW kit, I’m all ears.
          Seattle, WA
          currently:
          1988 M3 ex j-stock
          1984 911 RoW 3.2
          http://cars.g93.net

          Comment


          • #6
            springs are cheap and the KW's probably use a standard size spring, so if they turn out too soft, can just get stiffer springs. it would be nice to know what the rate is though..

            fwiw, someone on the e30sig mentioned that the v1 and v3 use the same springs. difference is the adjustable dampers on the v3. no personal knowledge to confirm this.
            88 M3 Henna
            95 M3 Orange
            97 M3 Techno

            Comment


            • #7
              Originally posted by mlytle View Post
              fwiw, someone on the e30sig mentioned that the v1 and v3 use the same springs. difference is the adjustable dampers on the v3. no personal knowledge to confirm this.
              That was me . . .

              Here is the TUV document for both the Variant 1 and Variant 3. Note that both versions use the same spring nomenclature.

              https://www.kwsuspensions.com/extras...DB_1059-20.pdf

              A couple of items noted:
              1) Front main spring is 140mm tall (5.5 in) - untensioned height. It is a linear spring. Appears the ID is 70mm.
              2) The front tender spring is 80mm tall (3 in)
              3) Rear springs are 170mm tall (6.7 in) - untensioned height. It is a progressive spring.
              4) Unfortunately no springs rates are given on the TUV document.

              Mark
              1990 M3

              Usually it's best not to know how much money you have into your M3

              Comment


              • #8
                Dave the J-Stock setup is a bit too stiff for a 2600# car. run 700# front 900# rear (stock rear spring location) and disconnect the rear sway bar. Modify the ramp angles in the diff and you will LOVE how it handles.

                I have a backup set of AST 4250 rear doubles I am looking to sell BTW, and if you need a built diff I have a 3.73 with modded ramp angles I can part with as well.
                sigpic
                2010 BMW Club Racing E30 M3 Touring Car Champion
                2011, 2013 SCCA Runoffs Super Touring Under 3.0L Bronze Medalist
                2011 SCCA Jim Fitzgerald Rookie of the Year
                2012 SCCA Northeast Divisional STU Champion
                2015 SCCA Runoffs STU Polesitter

                Comment


                • #9
                  Thanks Eric, that’s really helpful.
                  Just to make sure I’m clear - you mean 2600lb without driver or?

                  Also - thanks for the offer on the diff. My gearbox is the standard US box, so unless I get a line on a reasonably priced dogleg box, I probably want to go shorter for the final drive vs taller, I think.
                  Seattle, WA
                  currently:
                  1988 M3 ex j-stock
                  1984 911 RoW 3.2
                  http://cars.g93.net

                  Comment

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