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AC Schnitzer subframe "spacers"

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  • #16
    I've just taken another look at those ACS spacers and it looks like with the shape of the machined surface fitting downwards, as described in their instructions, there is absolutely no movement of the subframe possible in the horizontal plane (fore/aft/lateral) and so the subframe bushes can only allow a small amount of vertical movement only. They should work very well.

    /// Exdos ///
    "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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    • #17
      Ive been circuit racing for years, and rallyin decades before that. Ive been doing a lot of research of the suspension geometrics. The alloy plate ASC sell with the kit, does it drop rear suspension by its thickness? If it goes between body and bush, it does more than stiffen the bush. If the rear subframe drops it will will drop rear rollcenter making the whole roll axis to move. Dropping the subframe would move the understeer-oversteer balance to understeer. Changing 5mm will make a total difference in balance. I cannot figure out from the pictures whether it goes on top of the stock bush aluminum center, or around it, on top of the rubber? If its around it it will just press the rubber tighter, making the feel stiffer.
      Last edited by 131; 23-06-2011, 06:01 AM.

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      • #18
        If you take a close look at the subframe on the MC in situ, you'll see that there is a gap of about 10mm between the top of the subframe (and bush) and a large circular disc on the underside of the body where the subframe pin is bolted. The ACS disc fits into that gap and so goes on top of the OEM bush and because the ACS disc is lipped, it will sit inside the subframe, thus preventing, fore/aft and lateral movement of the subframe.
        /// Exdos ///
        "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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        • #19
          So subframe location dont move? Ok, then it only stiffens it.

          But, if someone races on track, you could adjust the balance by lifting or dropping the subframe. Factorybuild E30 M3 DTM racers had it adjustable.

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          • #20
            Originally posted by 131 View Post
            But, if someone races on track, you could adjust the balance by lifting or dropping the subframe. Factorybuild E30 M3 DTM racers had it adjustable.
            Since the subframe also acts as the diff carrier, if you were to move the subframe closer to the body, then you'd also be moving the propshaft closer too and I'm not sure how much clearance there is to do that. OTOH, you could move the subframe away from the body, but would you want to do that?

            Does adjusting the subframe relative to the body have much of a difference to adjusting the rear ride height on the spring perches, as with aftermarket adjustable suspension kits, provided that you also adjust camber and toe accordingly?
            /// Exdos ///
            "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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            • #21
              Interesting, you can imagine that raising the subframe up especially if you've lowered the car will reverse some of the extra camber/toe. The only issues as said is the angle of the propshaft but this should have enough give in the joint, the rear diff bush does definitely, so it would all raise up together.

              It's a shame the diff's mounted on the subframe otherwise you could play about with this easier (also clearance from the boot floor isn't that great above the diff at it's highest point).

              I don't imagine it would affect the ride height much/at all, the angle of the trailing arm where the spring sits is moving all the time anyway, it may just re-angle it slightly but not enough to change the ride height noticeably IMO.

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              • #22
                Originally posted by c_w View Post
                It's a shame the diff's mounted on the subframe otherwise you could play about with this easier (also clearance from the boot floor isn't that great above the diff at it's highest point).
                Also the Diff is mounted to the subframe AND also the "ear" which is attached to the body, so you'd have to modify that too. On a racecar you could cut through the boot floor and make a much stronger and height adjustable bracket to attach the diff.
                /// Exdos ///
                "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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                • #23
                  http://www.e30m3project.com/e30m3per...m_pickup-1.jpg

                  In this picture you can see how the DTM version had the roll adjustment. They had subframe bolted into body and the trailinarm could be moved up and down. Also the toe and camber were adjustable by separate adjustments. Moving the subframe does the same roll adjustment. It does change ride height a bit, but cause of the roll adjustment is +/- aprox 3mm maximum, the ride height changes propably cannot even be measured. Ride height changes cause the spring perch angle changes slightly twisting the spring a bit. This isnt significant change. Also the diff mounting is so flexible it dont need anything done. Shaft angles dont change either too much. But, I dont suggest anybody to do such adjustment, except if theyr racing and are lookinf for the last tenth of the second. To clubracers its easier to change toe or rear ride height to make car understeer/oversteer as wanted. For serious racers this is one important place to make adjustments. Forexample, you can choose the cars ride height as you want, then adjust the roll axis to make the car handle as you wish, along with the other adjustments.
                  http://www.131abarth.com/bmw_325.htm some pics of our racer. Going to 24 hours race in three weeks, should make some slight maintenance to make it do the whole race! We won it last year.

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                  • #24
                    Originally posted by exdos View Post
                    Also the Diff is mounted to the subframe AND also the "ear" which is attached to the body, so you'd have to modify that too. On a racecar you could cut through the boot floor and make a much stronger and height adjustable bracket to attach the diff.
                    As said I reckon the diff ear would have enough give if the subframe is raised 10mm. The subframe probably moves more than that in normal use anyway on the standard front bushes!

                    Looks like the E30 race setup was quite different though.

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                    • #25
                      Originally posted by c_w View Post
                      Looks like the E30 race setup was quite different though.
                      Very little like the OEM set-up. With many of these racecars there's barely any similarity to the production car to which they are supposed to be.
                      /// Exdos ///
                      "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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                      • #26
                        found this picture on a old thread of the spacer fitted,

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                        • #27
                          Dave,

                          Thanks for that, I'll put that in a current thread on the zroadster forum.
                          /// Exdos ///
                          "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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