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Should new Bilstein sports feel this still.

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  • m3pat2
    replied
    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?

    Leave a comment:


  • stevesingo
    replied
    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 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

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  • caneswell
    replied
    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?

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  • caneswell
    replied
    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.

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  • hardtailer
    replied
    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.

    Leave a comment:


  • stevesingo
    replied
    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.

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  • hardtailer
    replied
    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

    Leave a comment:


  • hardtailer
    replied
    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.

    Leave a comment:


  • stevesingo
    replied
    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.

    Leave a comment:


  • caneswell
    replied
    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!?

    Leave a comment:


  • autox320
    replied
    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.

    Leave a comment:


  • caneswell
    replied
    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

    Leave a comment:


  • stevesingo
    replied
    Any chance of a translation?

    Leave a comment:


  • stevesingo
    replied
    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?

    Leave a comment:


  • hardtailer
    replied
    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?

    Leave a comment:

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