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Thread: Main Tire Alignment Spec

  1. #1

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    Default Main Tire Alignment Spec

    Hi All,
    I measured the Toe-In on the mains on my S7 and was surprised to see almost an inch of Toe-In (7/8" to be exact). I'm currently flying on 8" tires with the stock Grove spring gear suspension.

    This would be considered way out of spec on most any automotive application, but I don't know if this is what is needed on a Tailwheel Kitfox. I've seen the axle shims that Kitfox has in their parts catalog, but before I do anything I need to know the specs. I did a search here, but didn't see anything so if I missed it I apologize.

    Any info or direction would be appreciated. - Mark

  2. #2
    Senior Member jrevens's Avatar
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    Default Re: Main Tire Alignment Spec

    Mark - is that in the 3-point attitude or level?
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

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    Default Re: Main Tire Alignment Spec

    Quote Originally Posted by jrevens View Post
    Mark - is that in the 3-point attitude or level?
    Great Question I didn't even think of that. I measured in a 3 point attitude. Does the procedure call for checking in level attitude? - Mark

  4. #4
    Senior Member jiott's Avatar
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    Default Re: Main Tire Alignment Spec

    Yes, you check it in level flying attitude. A perfect zero toe-in level will show toe-in when in 3-point. The Grove gear has the axle mount pads machined to a very close tolerance, so it is unusual to find much of any toe-in unless the gear has been bent. The welded cabane type gear is much more likely to have toe-in/out.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

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    Senior Member rv9ralph's Avatar
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    Default Re: Main Tire Alignment Spec

    Here is a link to Grove Aircraft information on checking landing gear alignment. It also has a table to what shim will be required depending on how far out your alignment is.

    Here is the link: https://www.groveaircraft.com/accessories.html

    Ralph

  6. #6
    Senior Member jrevens's Avatar
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    Default Re: Main Tire Alignment Spec

    The Grove gear generally has quite a bit of positive camber, and is (as far as I have seen) formed for the axle mount surfaces to be horizontally parallel in the level attitude. That will give you toe-in as the gear is rotated to 3-point. That decreases when the airplane is loaded & heavier, & the gear flexes of course. I decided that since the vast majority of on-the-ground operation is 3 point that I would shim my axles to give me parallel wheels in 3-point, and slight toe-out when level. Slight toe-out is actually stabilizing, vs toe-in which is de-stabilizing. You could also shim for no toe-in or out (neutral) in either position, but that will likely give you more toe-out when the airplane is loaded more heavily and has negative camber the 3-point attitude.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  7. #7

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    Default Re: Main Tire Alignment Spec

    Quote Originally Posted by rv9ralph View Post
    Here is a link to Grove Aircraft information on checking landing gear alignment. It also has a table to what shim will be required depending on how far out your alignment is.

    Here is the link: https://www.groveaircraft.com/accessories.html

    Ralph
    Ah, perfect. Thank you for pointing this out. It's much appreciated. - Mark

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