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  1. #1
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    Default Which one makes a bigger differnce

    Changing bar length or mounting height on birdcage. Standard length B/G Rocket length mounted at 11" spread on birdcage. I am way better at engine stuff than suspension, just learning as we go.

  2. #2
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    Quote Originally Posted by Mopar DLM View Post
    Changing bar length or mounting height on birdcage. Standard length B/G Rocket length mounted at 11" spread on birdcage. I am way better at engine stuff than suspension, just learning as we go.
    Not quite enough info on what you want to change here, but in general, changing a bar length, where you are moving the frame end, and maintaining the ride height wheelbase, is a pretty small change. Changing location on the birdcage can be a very significant adjustment.

    That 11", if you are measuring in a straight line from upper mount to lower mount on cage, is not a standard length.
    Last edited by MasterSbilt_Racer; 04-18-2022 at 01:41 PM.
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  3. #3
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    The top bar is at the correct measurement but the bottom bar is currently mounted way to far down on the cage per Rockets specs. In a perfect world with all other things being correct, if only moving the bottom bar up closer to axle tube on the cage side and move frame side to keep angles correct what would kind of changes would we most likely see. Just generally speaking. I know there are timing changes and extended load changes but just wondering if there is a suspension for dummies answer. If you move the bar it makes the car ____ here.

  4. #4
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    Quote Originally Posted by Mopar DLM View Post
    The top bar is at the correct measurement but the bottom bar is currently mounted way to far down on the cage per Rockets specs. In a perfect world with all other things being correct, if only moving the bottom bar up closer to axle tube on the cage side and move frame side to keep angles correct what would kind of changes would we most likely see. Just generally speaking. I know there are timing changes and extended load changes but just wondering if there is a suspension for dummies answer. If you move the bar it makes the car ____ here.
    Moving that lower up removes thrust angle, removes birdcage index, and adds loose roll steer.

    Car should be quite a bit looser on the throttle.
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  5. #5
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    And that my friends is why 4m has some of the best people in racing. Quick, precise, relatable, and useable information that helps people go faster. Thanks MasterSbilt

  6. #6
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    Default

    Quote Originally Posted by Mopar DLM View Post
    And that my friends is why 4m has some of the best people in racing. Quick, precise, relatable, and useable information that helps people go faster. Thanks MasterSbilt
    Also keep in mind you probably changed the trail on the LR if you move that. Since the frame holes are on an arc and the cage has the extra hole either straight down or possible slanting forward as you go down.
    Last edited by billetbirdcage; 04-20-2022 at 01:56 PM.

  7. #7
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    Quote Originally Posted by Mopar DLM View Post
    And that my friends is why 4m has some of the best people in racing. Quick, precise, relatable, and useable information that helps people go faster. Thanks MasterSbilt
    You are welcome. Billet did add a potentially important detail as well. You will want to check that once you finish. I'd probably find a flat spot to check cage angle before and after your adjustment. Adjust bottom bar length to get the angle back.
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  8. #8
    Join Date
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    Quote Originally Posted by MasterSbilt_Racer View Post
    Moving that lower up removes thrust angle, removes birdcage index, and adds loose roll steer.

    Car should be quite a bit looser on the throttle.
    Removes index? How so?

  9. #9
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    Default

    reducing angle reduces index ...

  10. #10
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    Quote Originally Posted by ukydude View Post
    Removes index? How so?
    The lr birdcage typically rotates counter-clockwise, when looking at wheel, during droop travel. The lr bottom bar works the opposite, trying to pull the bottom of the cage forward. It's just that the top bar wins out on which way the cage rotates. With angle the same, but the lr bottom bar further from the axle centerline, it's pull forward results in less contribution to clockwise rotation. It pulls forward just as much, but due to longer moment arm, the angle of rotation it effects is less.
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  11. #11
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    Quote Originally Posted by MasterSbilt_Racer View Post
    The lr birdcage typically rotates counter-clockwise, when looking at wheel, during droop travel. The lr bottom bar works the opposite, trying to pull the bottom of the cage forward. It's just that the top bar wins out on which way the cage rotates. With angle the same, but the lr bottom bar further from the axle centerline, it's pull forward results in less contribution to clockwise rotation. It pulls forward just as much, but due to longer moment arm, the angle of rotation it effects is less.
    Yes...you said bottom up removes index.

  12. #12
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    Quote Originally Posted by ukydude View Post
    Yes...you said bottom up removes index.
    I sure did, twice now. Less clockwise rotation influence results in MORE counter-clockwise rotation, the rotation that we actually see.
    Last edited by MasterSbilt_Racer; 04-21-2022 at 12:37 PM.
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  13. #13
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    It's been brought to my attention that my comments about index are incorrect if your top bar is at 12 oclock and bottom at 6 oclock, as has been historically the norm. If the top is cheated back and bottom forward, like a "zero index", then what I said above about index is likely correct.
    Last edited by MasterSbilt_Racer; 05-02-2022 at 05:44 AM.
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