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  • #61
    The source is here: http://www.s14.ctmnet.de/0053/0053.htm
    Ride height is given for a 15" wheel (foot note 2) with 205/55r15 tyres. 16" with 225/45r16 are not 13mm taller!
    All data given is valid for konstruktionslage='design height' where there is a 68kg driver And passenger on each front seat And one or two (I dont know unfortunately) 68 kg passenger on the rear seats. Each has 7kg in the trunk, I.e. 21kg. This info stems from the German equivalent of the Haynes manual 'jetzt helfe ich mir selbst'.
    Your correct in the bump and rebound travel as translation for f-weg ein and ...aus.

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    • #62
      Originally posted by caneswell View Post


      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
      That's not how motion ratio is calculated...
      It is the cosine of the angle between horizontal and the connecting line between tyre contact patch and roll centre times the cosine of the angle between vertical and strut in front view, if I'm not mistaken

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      • #63
        Originally posted by hardtailer View Post
        The source is here: http://www.s14.ctmnet.de/0053/0053.htm
        Ride height is given for a 15" wheel (foot note 2) with 205/55r15 tyres. 16" with 225/45r16 are not 13mm taller!
        All data given is valid for konstruktionslage='design height' where there is a 68kg driver And passenger on each front seat And one or two (I dont know unfortunately) 68 kg passenger on the rear seats. Each has 7kg in the trunk, I.e. 21kg. This info stems from the German equivalent of the Haynes manual 'jetzt helfe ich mir selbst'.
        Your correct in the bump and rebound travel as translation for f-weg ein and ...aus.
        That is a great resource, if you speak German. Haha.

        RE Ride height. If the ride height is measured from the wheel arch lip to the bottom of the wheel rim, fitting a 16" wheel will not change the distance from the wheel centre to the wheel arch, but it will add 1/2 of the diameter increase, i.e 13mm.
        Sport Evo No.47

        My Sport Evo Restoration

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        • #64
          When changing wheel diameter the sidewall height of the tyre changes such that the tyre diameter remains (almost) the same.

          Apart from that the definition of ride height in this case is the distance between the road surface and the center of the wheel hub.

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          • #65
            Originally posted by hardtailer View Post
            That's not how motion ratio is calculated...
            It is the cosine of the angle between horizontal and the connecting line between tyre contact patch and roll centre times the cosine of the angle between vertical and strut in front view, if I'm not mistaken
            Yes. That makes sense now I've thought about it more. It's not to do with lever arm lengths for struts. It's just the resultant of the angle the strut make to the vertical.

            It's only on the rear end semi trailing arms that lever arm length should be considered.
            If everything seems under control, then you're just not going fast enough...

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            • #66
              Surely this all means we should basically remove almost all of the bump stops in order to get some sensible wheel travel before they contact?
              If everything seems under control, then you're just not going fast enough...

              Comment


              • #67
                Originally posted by hardtailer View Post
                When changing wheel diameter the sidewall height of the tyre changes such that the tyre diameter remains (almost) the same.

                Apart from that the definition of ride height in this case is the distance between the road surface and the center of the wheel hub.

                I disagree.

                You cant take a measurement from the road surface to the centre of the hub as a valid measure of ride height. Such a measurement is a measure of wheel and tyre radius.

                Am certain the BMW method of measuring ride height is from lower lip of wheel to edge of wheel arch. An example can be seen on P30 of this PDF. It also explains that for every 1 increase of wheel diameter we must add 13mm to the measurement.

                http://www.bmwclub.lv/files/BMW_X5_S...on_Systems.pdf
                Sport Evo No.47

                My Sport Evo Restoration

                Comment


                • #68
                  Thanks for the great info. on cutting the bump stops Steve. Can someone confirm that I won't have to worry about the pressurized gas if I attempt to trim my bump stops on the Billy Sports?
                  Pat

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                  • #69
                    The bump stops sit outside of the pressurised chamber, so no worries.

                    http://www.r3vlimited.com/board/showthread.php?t=239380
                    Sport Evo No.47

                    My Sport Evo Restoration

                    Comment


                    • #70
                      So does anyone with Billy sports that feel "right" have a ride height measurement they can share? After raising my car I am sitting at ~13" from center of the wheel to the fender on the front, and ~12" at the rear. Just curious if this should be high enough to get the billy sports from riding on the bump stops, or if I should go higher or cut the bump stops down.

                      EDIT - think I found what I wanted - http://s14net.vbulletin.net/forum/s1...ight-samplings

                      Comment


                      • #71
                        Originally posted by stevesingo View Post


                        I disagree.

                        You can’t take a measurement from the road surface to the centre of the hub as a valid measure of ride height. Such a measurement is a measure of wheel and tyre radius.

                        Am certain the BMW method of measuring ride height is from lower lip of wheel to edge of wheel arch. An example can be seen on P30 of this PDF. It also explains that for every 1” increase of wheel diameter we must add 13mm to the measurement.

                        http://www.bmwclub.lv/files/BMW_X5_S...on_Systems.pdf
                        Oops, you are right...I had a few things mixed up there. Your remark that from the wheel center to the pavement one would be measuring tyre radius switched on the light for me :-)

                        Comment


                        • #72
                          Originally posted by Daniel View Post
                          So does anyone with Billy sports that feel "right" have a ride height measurement they can share? After raising my car I am sitting at ~13" from center of the wheel to the fender on the front, and ~12" at the rear. Just curious if this should be high enough to get the billy sports from riding on the bump stops, or if I should go higher or cut the bump stops down.

                          EDIT - think I found what I wanted - http://s14net.vbulletin.net/forum/s1...ight-samplings
                          From what we've concluded so far that 13" measurement would be compressing the bump stops 1.6 inches and be almost locked solid.....I think we are missing something here!!

                          I think the change in camber means that the motion ratio is not 0.93 at the outer wheel rim.....,no idea what it is though :-)
                          If everything seems under control, then you're just not going fast enough...

                          Comment


                          • #73
                            Originally posted by caneswell View Post

                            From what we've concluded so far that 13" measurement would be compressing the bump stops 1.6 inches and be almost locked solid.....I think we are missing something here!!

                            I think the change in camber means that the motion ratio is not 0.93 at the outer wheel rim.....,no idea what it is though :-)
                            It does seem like it. My before measurements from the ground were 23 3/8" front, 23" rear, and after from the ground are 24 3/8" front 23 3/8" rear. It seems a lot of those folks running Billy/H+R were at about the same as me now.

                            Comment


                            • #74
                              Originally posted by stevesingo View Post
                              The bump stops sit outside of the pressurised chamber, so no worries.

                              http://www.r3vlimited.com/board/showthread.php?t=239380

                              Thanks Steve! I should have probably read through all the links, but I haven't had much time lately.
                              Pat

                              Comment


                              • #75
                                I spent yesterday measuring , stripping, examining, ect my Bilstien inserts.

                                Firstly I took a measurement of the compressed strut (spring plate to spring plate) with the car sat on flat ground- 112mm.

                                Measured front ride height- 570mm (16 wheel Sport Evo fender-Equivalent to 560mm with 16 wheel and Stock fenders and 557mm 15 wheel with stock fender)

                                Then raised the car and measured the extended strut (spring plate to spring plate) - 240mm

                                If we take the compressed measurement from the extended measurement 240-112= 128 mm compression.

                                We believe the Bilstien has 82mm travel before the bump stops, so it would seem that the car is sat on the bump stops and compressing them by 128-82= 46mm

                                To confirm this I stripped the struts and measured the travel.

                                Extended -120mm

                                PIC

                                Compressed by hand 20mm

                                PIC

                                So I have 18 mm more travel than we think I should have. Why?

                                I pulled the inserts and knocked off the end caps (Simple!) and this is what I found.

                                PIC

                                Bump stops are shot to pieces! This was the same both sides. The car must have been riding on these the whole time, so it is not surprising they let go.

                                I estimate that the bump stops were about 80mm long and the length of the rod is 160mm in total, so that would make sense of the 82mm travel as stated by Bilstien.

                                I was left with no choice but to trim off the damaged portion which left me with 25mm of bump stop and put them back together. This leaves me with 135mm of free travel in the shock before the bump stops take effect.

                                How much travel do we need? Well, I am already on 128mm of compression, so I have 7mm remaining before the bump stops.

                                The other consideration is the spring becoming coil bound. This would be a serious issue as the suspension becomes solid in such a case.

                                My spring is 240mm long and is made of 6 coils of 13mm wire. Its coil bound length is 6*13= 78mm. Take this from the compressed length and we should get the remaining travel 240-78=162mm of spring travel, or 2mm more than the total shock travel less bump stops.

                                Conclusion- I will not become coil bound before the bump stops take effect. All OK on that front!

                                After putting it back together I went for a short drive and it is more supple on the front end. A longer more spirited drive will be needed before a full conclusion can be made.

                                For the record the whole effort took about 2 hrs.
                                Sport Evo No.47

                                My Sport Evo Restoration

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