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Should new Bilstein sports feel this still.

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  • #46
    The Bilstein rep also stated that their shocks could be compressed a further 65mm on the bump stops up to their max test load of 5000N, so they must be significantly longer than the stock versions...

    Why are they designed to basically run on their bump rubbers??
    If everything seems under control, then you're just not going fast enough...

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    • #47
      So basically I need to trim my Bilstein's bump stops!

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      • #48


        I did some Googling and it would seem the Bilstein bump stops are about 75mm long



        And if this E28 example is anything to go by, available in different hardness.




        Sport Evo No.47

        My Sport Evo Restoration

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        • #49
          OK so measuring at the wheel rim (16x8 ET23) i'm getting ~105mm of travel from rest to fully extended on my standard (>170k mile!!) front springs.

          I've measured the motion ratio whilst I was there at ~0.62 (the ~0.9 numbers stated online are for the centre of the contact patch, so quite different at the edge of the rim)

          This means I'm sat at 65mm of shock compression from a total 82mm. Giving me 28mm of wheel rim travel before they contact, which doesn't seem to be very much and the bump rubbers must be very soft as I'm not noticing a sharp increase in rate when driving. Certainly seems like you will have to trim them when lowering. I'll see if my Bilstein contact has any feedback as to why they are like this.
          If everything seems under control, then you're just not going fast enough...

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          • #50
            Good info. What is your ride height from bottom of wheel rim to wheel arch?

            My ride quality on 155lb/in front spring at stock ride height is pretty good mostly. Where I do notice an imbalance front to rear is when hitting compressions at speed. The front does feel quite firm compared to the rear. I think I will conduct the same test as you at the weekend.
            Sport Evo No.47

            My Sport Evo Restoration

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            • #51
              565-570mm left to right (probably not the most level driveway) How does that compare? Wheel looks to be pretty concentric in the arch.
              If everything seems under control, then you're just not going fast enough...

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              • #52
                Mine is about the same, although I have the Sport Evo front fenders/wings which have a 10mm larger arch, so I would say I am using 10mm more of the available wheel travel than your good self.
                Sport Evo No.47

                My Sport Evo Restoration

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                • #53
                  Originally posted by caneswell View Post
                  I've measured the motion ratio whilst I was there at ~0.62 (the ~0.9 numbers stated online are for the centre of the contact patch, so quite different at the edge of the rim.
                  Which travels did you measure and how did you calculate your motion ratio?
                  Since the edge of the rim is solidly attached to the contact patch the motion ratio at the edge of the rim has to be the same.
                  One of main characteristics of a McPherson strut suspension is that the motion ratio is almost 1, apart from that the motion ratio of 0.9 stems from official BMW documents, so it would be a shame if you'd base further calculations or decisions on a wrong assumption.

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                  • #54
                    This is the source for the motion ratios:

                    About halfway of the page where it says FederÜbersetzung and DämpferÜbersetzung



                    Rear suspension:



                    PS anybody noticed that the thread starter never replied/reacted to all the valuable info in this thread?

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                    • #55
                      Originally posted by hardtailer View Post
                      PS anybody noticed that the thread starter never replied/reacted to all the valuable info in this thread?
                      Who cares? I find some of the best catalysts for discussion come from nowhere.

                      That info is gold dust, thanks for posting. What is the document?
                      Sport Evo No.47

                      My Sport Evo Restoration

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                      • #56
                        Any chance of a translation?
                        Sport Evo No.47

                        My Sport Evo Restoration

                        Comment


                        • #57
                          Originally posted by hardtailer View Post
                          Which travels did you measure and how did you calculate your motion ratio?
                          Since the edge of the rim is solidly attached to the contact patch the motion ratio at the edge of the rim has to be the same.
                          One of main characteristics of a McPherson strut suspension is that the motion ratio is almost 1, apart from that the motion ratio of 0.9 stems from official BMW documents, so it would be a shame if you'd base further calculations or decisions on a wrong assumption.

                          I was looking at it like this:

                          http://www.worksevo.com/Spring_Rates_1.pdf

                          ...and then taking it to the edge of the rim.

                          However I think those dimensions are wrong. As you say the hub assembly will move vertically with the outer ball joint, so the correct numbers are the distance from outer ball joint to lower shock mount. Rather than the contact patch. Which will be much closer to 1:1
                          If everything seems under control, then you're just not going fast enough...

                          Comment


                          • #58
                            If you guys drive hard and I know you are then your on the stops. Trim until you only have one bump knuckle on the shaft and the issue goes away. Travel is restored. I'm on the FIA rumbles all the time at VIR and it's mainly possible due to trimmed stops. Rode in a e30 with the stops and the front went hard through the esses. Not a good place to lose compliance where your pucker factor is already an 8.

                            An old autocross trick is to put a zip tie on the base of the shaft. Go drive and see where it ends up. Then account for the bumpstop.
                            Photos

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                            • #59
                              So if the motion ration value is in the region of 0.93 then these shocks are running on the bump stops sat on the drive......with the highest ride height springs anyone ever fits....surely that can't be the intention!?
                              If everything seems under control, then you're just not going fast enough...

                              Comment


                              • #60
                                Trying my best to translate the above document...

                                hohenstand = ride height 556mm presumably with 15" wheel which is equal to 569mm with a 16" wheel.

                                Federweg Ein = Travel a (possibly compression)? 95mm
                                Federweg Aus = Travel from (Possibly rebound)? 75mm

                                Add them together we 170mm of travel. Multiply by the motion ratio and we get 170*0.9326=158mm of shock travel. Compared to the 82mm of the Bilstein, I must be missing something.

                                That is if google translate for German is any good.
                                Sport Evo No.47

                                My Sport Evo Restoration

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