Does wheel size -tire height- influence lean angle?

Discussion in 'The Perfect Line and Other Riding Myths' started by scootrboi, Apr 22, 2014.

  1. khager

    khager Long timer

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    Ok, so for example my Wee-Strom with its high CG and skinny 19" tire, do I have to lean over more to carry the same speed thru a corner as say a GSXR with fatter 17" rubber and lower CG?
    #21
  2. scootrboi

    scootrboi Long timer

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    I think you have it backwards. When he says 'higher lean angle' he means leaning over further toward the ground. At least that is what the diagram says to me.
    #22
  3. lnewqban

    lnewqban Ninjetter

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    It is the other way around. :1drink
    Lean angle is measured from a vertical line.

    What really matters to absolute (system) lean angle (which generally differs form the angle the bike or frame leans) is the CG and the point of contact with the road.
    How the bike and rider accommodate themselves to that fixed angle depends on tire profile, relative (to that profile) height of CG and hanging-off effect.

    The mass or weight does not matter; light or heavy, the angle formed among the CG, point of contact and vertical is exactly the same for equal radius of turn and speed.
    As you can see in the schematic below, the mass in the centrifugal force (horizontal force) cancels the mass in the weight (vertical force).

    [​IMG]

    [​IMG]
    #23
  4. klaviator

    klaviator Long timer

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    Your Wee will lean slightly less than your GSXR for the same speed but the difference is very small. Furthermore, you wee will run out of clearance before your GSXR will, limiting cornering speed
    #24
  5. scootrboi

    scootrboi Long timer

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    What influence does the wheelbase have?
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  6. lnewqban

    lnewqban Ninjetter

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    As far as I know, no influence.
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  7. klaviator

    klaviator Long timer

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    #27
  8. khager

    khager Long timer

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    Thanks, I never was good at physics.:lol3.
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  9. outlaws justice

    outlaws justice Long timer

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    Now when a rider starts to move his center-line inside the bikes center-line (Especially the upper body) that has a great impact on the Combined center of gravity, and moves that in so it is more in line or even inside the line from the contact patch.
    #29
  10. lnewqban

    lnewqban Ninjetter

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    The Combined center of gravity remains in the same position.
    What the rider does by moving his CG in is pushing the bike out a couple of degrees (more vertically).
    The lateral forces on the contact patches remain the same, but the suspension gains those couple of degrees to work just a little better.

    [​IMG]
    #30
  11. lnewqban

    lnewqban Ninjetter

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  12. tkent02

    tkent02 Long timer

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    Wheelbase matters a lot…

    I can't ride anything as fast down a tight winding canyon as my DR200, the bigger the bike the slower I can ride it on the steep downhill sections where power doesn't help. Going uphill it's a differnt story. Seen 250s tear up full sized racebikes in the tightest sections, get left in the dust on the straights and catch back up when they get back into the tight curves, passing the liter bikes right and left. It's not a matter of having to horse all that weight around, it has to be the short wheelbase that does it. Anytime I can compare two similar bikes of different sizes, the smaller bike always blows away the big one in the tightest corners, especially as in the downhill example when power doesn't help much. Sooo much easier to ride a little bike faster in twisties.

    I think the part about two points on a circle in that other thread a few posts back explains it. What I don't get is how such a small change in wheelbase can have such a huge effect on cornering.
    #32