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    #1

    Rear Suspension Advice

    Hey everyone, I want to get your advice about how I should modify my rear suspension for my intents.

    The car is not a daily, just a second car that I'd like to get back into open lapping with. Sunday Funday car.
    ​​​​​​
    I am building custom coilovers built around koni sa IX shocks upfront and koni sa M3 shocks out back. Eibach springs with undecided rates but leaning towards 650/350.

    Primarily, I want to get the suspension geometry right. For track fun purposes.

    I was planning on the subframe risers from Condor and the eccentric adjustment kit.

    What I'm looking at now is IRP's rear DTM style camber/ toe adjustment. With standard subframe bushings, Condor would be my choice.

    The question centers around how well does the rear end grip with the risers and eccentrics? I feel it's going to be flawed due to me thinking that it will likely be toeing out under bump with this setup. I do not want a drift car.

    ​​​​​​​I don't want to do eccentrics now and then redo everything later, has anyone experienced both? Suggestions? I feel like I might be over thinking this...
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    #2
    My thougths are as follows, please let me know if they are correct.

    Despite whatever the toe/ camber values are, they change in direction at the horizontal point. I am thinking horizontal is center of the wheel/axle and the front pickup points of the control arms. At normal ride height, as things start compressing, you gain camber and TOE-IN (correct?). I spent some time underneath the car today but short of cutting my bumper off could not really figure out if this is the actual relationship. I would think it would be like this per design?

    If this is the case, I think I may do the eccentrics and riser bushings so long as I'm past the horizontal point and will not induce an increase in toe on compression.

    Really makes me wonder, if the above is the case. I really don't see the need for the DTM style camber/toe adjuster as made by MRT and IRP. Other than getting a spherical bearing in the inner joint/ heim joints and far greater range (not really useful if your not going to go there).

    The whole point of my concern is that with the eccentrics alone, I may not get the negative camber reduction I want and with the eccentrics+riser bushings do I have this weird thing happening where on bump im getting toe out. IF this is the case I will do the DTM style rear control arm mod, but if not I don't need it.

    Comment

      #3
      DTM style adjusters do NOT adjust sweep angle so there is a positive there. If you need much adjustment at all with any of the slotted adjusters the trailing arms will bind at an increasing rate as adjustment goes up.

      But you can not have an idea of how far out the alignment is until you get your ride height set.

      Spring, sway bar, rake, and High caster also have a great effect on rear grip.

      Find your ride heigh you want with the subframe bushing you want to go with, then check alignment and see where you want to go.


      I was up above it, Now I'm down in it ~ Entropy - A Build thread.
      @Zakspeed_US

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        #4
        Thanks. I'll figure out my desired ride height and go from there.

        Thoughts on the stim tech spherical RTABs? I don't understand how they will make up for the binding that would be introduced with eccentrics? I can't see the construction clearly.

        This is getting expensive fast, eccentrics plus these RTABs mount be more than the DTM style

        Comment

          #5
          Imagine taking A front door that has 2 hinges on it and putting eccentrics on them. The hinges have "zero" deflection they run on the same axis that is "Parallel" to the door. With the eccentrics you now have 2 axis running parallel with each other, and the more adjustment you need, the further out they are. How well do you think that door would operate?

          OK for rubber bushings or spherical where however much you adjust, you're just changing the angle of the axis and not the the separation of the axis.

          I have the Stim Tech spherical rtabs, was about 80% done designing my own kit when I found those units. The trailing arm moved up and down like butter. A+

          I was up above it, Now I'm down in it ~ Entropy - A Build thread.
          @Zakspeed_US
          • Likes 1

          Comment

            #6
            Originally posted by moatilliatta View Post
            Imagine taking A front door that has 2 hinges on it and putting eccentrics on them. The hinges have "zero" deflection they run on the same axis that is "Parallel" to the door. With the eccentrics you now have 2 axis running parallel with each other, and the more adjustment you need, the further out they are. How well do you think that door would operate?

            OK for rubber bushings or spherical where however much you adjust, you're just changing the angle of the axis and not the the separation of the axis.

            I have the Stim Tech spherical rtabs, was about 80% done designing my own kit when I found those units. The trailing arm moved up and down like butter. A+
            Did it stop the toe adjuster from moving on you as well?

            Do you think a pair would have been sufficient? I guess it would come down to the deflection allowed.

            I've asked, he doesn't sell them in pairs but they are pricey. Add to that I've already got condor RTAB's in hand.

            Comment

              #7
              NM, I think I just realized why a pair alone wouldn't work. Correct if I'm wrong pls.

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