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Thread: Overton's rr

  1. #1
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    Default Overton's rr

    Its quite a bit lower in dynamic than the others. I talked to two other national LH drivers, they said they see it but cant figure it out!
    An army of sheep led by a lion(Trump), is mightier than an army of lions, led by a sheep(Biden).

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    If all you do is lower the rr, car gonna wheelie.
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    Droop isn't the problem.

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    The real needed information needed is the contact patch pressure at all 4 wheels at a specific dynamic point in question.

    Travel needed to provide those weights can be achieved by any number of methods.

    Is this actually better because of the method used to achieve this attitude?
    Last edited by 95shaw; 03-12-2022 at 12:01 PM.

  4. #4
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    Quote Originally Posted by 95shaw View Post
    The real needed information needed is the contact patch pressure at all 4 wheels at a specific dynamic point in question.

    Travel needed to provide those weights can be achieved by any number of methods.

    Is this actually better because of the method used to achieve this attitude?
    This is very very much not how it works. With the tools we have, it impossible to calculate how much weight is on all 4 tires. Maybe Ghopper is getting close to simulating it, but linear shock positions tell you very little about how much weight is on said tire.

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    Quote Originally Posted by Austin34471 View Post
    This is very very much not how it works. With the tools we have, it impossible to calculate how much weight is on all 4 tires. Maybe Ghopper is getting close to simulating it, but linear shock positions tell you very little about how much weight is on said tire.
    That was my point. There is no way of knowing the weights on the tires by simply looking at the attitude of the car.

    Any mix of springs j bar settings, control arm positions, etc, can alter the actual dynamic weight seen by the contact patch.
    Trying to equate attitude with some specific handling characteristics is fruitless.

  6. #6
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    Quote Originally Posted by 95shaw View Post
    That was my point. There is no way of knowing the weights on the tires by simply looking at the attitude of the car.

    Any mix of springs j bar settings, control arm positions, etc, can alter the actual dynamic weight seen by the contact patch.
    Trying to equate attitude with some specific handling characteristics is fruitless.
    I see. I thought you were saying that spring loads at certain positions were representative of how much weight was on the tire. Your last paragraph is spot on.

  7. #7
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    Quote Originally Posted by Austin34471 View Post
    This is very very much not how it works. With the tools we have, it impossible to calculate how much weight is on all 4 tires. Maybe Ghopper is getting close to simulating it, but linear shock positions tell you very little about how much weight is on said tire.

    Blasphemy

    You mean if I increase the droop load on my LR shock at full extention by 200#, I'm not adding 200# more to the LR tire while going around the track?

    Hmmm, who would of thunk . . . next your gonna say that LR weight highly varies with the banking of the track too I suppose.

    ^all sarcasm^

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    Trying to equate attitude with some specific handling characteristics is fruitless.

    So you dont agree that Overtons car has more rear aero downforce?
    An army of sheep led by a lion(Trump), is mightier than an army of lions, led by a sheep(Biden).

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    Quote Originally Posted by ZERO25 View Post
    Trying to equate attitude with some specific handling characteristics is fruitless.

    So you dont agree that Overtons car has more rear aero downforce?
    I'm saying I can set the rr bars and bury the right quarter panel of the body into the track.

    Does that mean there is more aero downforce?
    I'm not feeling it

  10. #10
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    Better description: "more body roll, less body pitch compared to other generally fast Longhorn cars."

    This helps you look past the narrowly focused discussion about RR components and move on to system level response....that includes the resulting LF response and a few parts in between.

  11. #11
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    Quote Originally Posted by Ghopper View Post
    Better description: "more body roll, less body pitch compared to other generally fast Longhorn cars."

    This helps you look past the narrowly focused discussion about RR components and move on to system level response....that includes the resulting LF response and a few parts in between.
    I think I understand what you are saying.

    I know the RR tire is loaded by not only the RR spring and bars, but also the LR spring and bars, the j bar, and the lift arm. Any aero loads are applied to the contact patch through these routes.
    Not knowing if the setup is exactly the same as the other cars, there is no way to know the contact patch pressure on any of the tires.

    I realize that geometry changes loading as well, so travel at other corners has a bearing in relation to timing of weight transfer, making the LF important, especially at turn in, which sets up the whole corner.

    I cannot see how blindly assessing visual cues can deliver useful data without knowing more of the picture.
    Last edited by 95shaw; 03-17-2022 at 03:43 AM.

  12. #12
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    Quote Originally Posted by 95shaw View Post
    I think I understand what you are saying.

    I know the RR tire is loaded by not only the RR spring and bars, but also the LR spring and bars, the j bar, and the lift arm. Any aero loads are applied to the contact patch through these routes.
    Not knowing if the setup is exactly the same as the other cars, there is no way to know the contact patch pressure on any of the tires.

    I realize that geometry changes loading as well, so travel at other corners has a bearing in relation to timing of weight transfer, making the LF important, especially at turn in, which sets up the whole corner.

    I cannot see how blindly assessing visual cues can deliver useful data without knowing more of the picture.
    He's just better articulating what I said with my one sentence earlier in the thread (post2). Looking at the rr is like looking at an average height tree in the forest. It isn't half the story, nor do I think it's even much of the story. The pitch comment is the key to the whole analysis, IMO. I didn't want to go as far as to directly point that out.
    East Bay - 2
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    Florence -4
    Moler - 3
    Portsmouth -2
    Eldora - 3
    Brushcreek -2
    Lawrenceburg -1
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    Droop isn't the problem.

  13. #13
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    Quote Originally Posted by MasterSbilt_Racer View Post
    He's just better articulating what I said with my one sentence earlier in the thread (post2). Looking at the rr is like looking at an average height tree in the forest. It isn't half the story, nor do I think it's even much of the story. The pitch comment is the key to the whole analysis, IMO. I didn't want to go as far as to directly point that out.
    Rumley must not have a degree in forestry!
    An army of sheep led by a lion(Trump), is mightier than an army of lions, led by a sheep(Biden).

  14. #14
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    Rumley's most notorious achievement came before the cars were on bump stops on the rf, and chain limiters on the lr.
    As was indicated in a couple posts before, rr height is mostly dictated by chain length and stop rubber spring rate and height.
    With both of these at their physical limits the car teeters toward lf or rr.
    Lift arm and j bar can affect which of these car teeters toward. CG height and position as well as rr and lf spring rates also have an effect.
    I guess we should throw tethers in there as well.

    I'm not certain aero plays as much of a factor as some would let on
    Last edited by 95shaw; 03-19-2022 at 02:49 PM.

  15. #15
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    Quote Originally Posted by 95shaw View Post
    Rumley's most notorious achievement came before the cars were on bump stops on the rf, and chain limiters on the lr.
    As was indicated in a couple posts before, rr height is mostly dictated by chain length and stop rubber spring rate and height.
    With both of these at their physical limits the car teeters toward lf or rr.
    Lift arm and j bar can affect which of these car teeters toward. CG height and position as well as rr and lf spring rates also have an effect.
    I guess we should throw tethers in there as well.

    I'm not certain aero plays as much of a factor as some would let on
    Hold on. Guys been running bumps for like 15 to 20 years, depending on what percentage of the field makes it count.

    The car doesn't have to teeter between any two points. Most do teeter lf to rr, however.
    East Bay - 2
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    Moler - 3
    Portsmouth -2
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    35 Raceway - 1
    Droop isn't the problem.

  16. #16
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    If you can achieve desired wheel weights in dynamic, bumps and limiters are not needed. Might be what Rumley achieved with his "device".
    Near as I know, current setups use these as most means to arrive at those desired wheel weights have been outlawed.

    Dirt late model racing is headed to a formula type arrangement.

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    As a side note, karting is able to reach those dynamic numbers without separate suspensions.
    They effectively teeter as well.
    Last edited by 95shaw; 03-19-2022 at 06:13 PM.

  18. #18
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    Quote Originally Posted by 95shaw View Post
    If you can achieve desired wheel weights in dynamic, bumps and limiters are not needed. Might be what Rumley achieved with his "device".
    Near as I know, current setups use these as most means to arrive at those desired wheel weights have been outlawed.

    Dirt late model racing is headed to a formula type arrangement.
    Modern dlm suspension makes actual suspension function compromises to aid aero attack angle. Due to the fact we have lost every rule the suppressed aero downforce, the strategy is effective. That's where it is like formula.

    It's not really about mechanical wheel loading. It's about producing the correct thrust vector from the rear tires at the right time. This means there are plenty of load and alignment combinations that will achieve the same result for the driver.

    Rumley device, in short, was acknowledgement that the suspension works in both the compression and rebound directions and only looking at "getting up on the bars" means you may be screwing a lot of other stuff up.
    Last edited by MasterSbilt_Racer; 03-20-2022 at 07:31 AM.
    East Bay - 2
    Atomic - 2
    Florence -4
    Moler - 3
    Portsmouth -2
    Eldora - 3
    Brushcreek -2
    Lawrenceburg -1
    35 Raceway - 1
    Droop isn't the problem.

  19. #19
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    Please do tell.

    How are you achieving torque thrust vectors without mechanically loading the tires?

    The tires are the only contact with the track surface.
    Mechanical linkages are the only connection between chassis and tires.
    Yes, aero surfaces can help aim the chassis around the track. But is intimately connected to track by tires
    .
    I concede there are various ways to get the car around the track, but can still not see how visual cues give indication of how chassis is working the tires.

  20. #20
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    Quote Originally Posted by 95shaw View Post
    Please do tell.

    How are you achieving torque thrust vectors without mechanically loading the tires?

    The tires are the only contact with the track surface.
    Mechanical linkages are the only connection between chassis and tires.
    I never said tires were not loaded. I said there wasn't one magical set of numbers for the 4 wheels. The alignment of the front and rear axles changes the ideal load division.

    I'm also going to say running on a stop, either in compression or rebound, leaves the suspension less able to handle surface irregularities than a suspension that is still working.

    I'm also gonna say a car with a lower rr dynamic ride height and the lf off the ground will be beaten by a car with the same rr dynamic ride and the lf still aiding steering, all else being somewhat equal.
    East Bay - 2
    Atomic - 2
    Florence -4
    Moler - 3
    Portsmouth -2
    Eldora - 3
    Brushcreek -2
    Lawrenceburg -1
    35 Raceway - 1
    Droop isn't the problem.

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