airhead rims, whats the reason for the uneven "divots"

Discussion in 'Airheads' started by mfp4073, Aug 24, 2010.

  1. mfp4073

    mfp4073 Long timer

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    I have noticed on old wire spoke airheads there are divots around the rim, but the are not evenly spaced. Whats the reason for this?
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  2. Mr. B.

    Mr. B. Climate Controlled

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    I've been told it is a safety feature to keep the tire on the rim in case of a flat. I assume that its true........can anyone back that up?
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  3. mfp4073

    mfp4073 Long timer

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    Wouldnt they be evenly spaced then?

    image for those who dont understand what I am talking about!
    [​IMG]
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  4. peterman

    peterman cop magnet

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    I have no knowledge of this for certain, but I imagine they are part of the manufacturing process used as a way to hold the rim from the internal side, once it has been rolled and welded. It would be interesting to watch the entire wheel making process from flat steel bands to a finished rim, for example, when are the spoke holes and dimples put in? After rolling, or before?
    I'd imagine afterwards,,,anyone watched rims being made?
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  5. Bill Harris

    Bill Harris Confirmed Curmudgeon

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  6. jdiaz

    jdiaz .

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    I've heard the same thing.
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  7. Wirespokes

    Wirespokes Beemerholics Anonymous

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    They're not all the way around the rim because...

    ... it would negate the reason for the dropped center, making it difficult or impossible to mount a tire. Take a look, and you'll see they're evenly spaced from the valve stem. The valve stem itself probably acts as one of the humps.

    Duane does talk about it on his site. And it is a safety thing I've only seen on BMW wire wheels, intended to keep the tire on the rim should it suddenly deflate.
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  8. Xcuvator

    Xcuvator Justa Venturer

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    I have heard that they are to prevent the bead from breaking but I never have been able to figure out how those little dimples could accomplish such a task.
    I just don't see how they could, since they don't protrude far enough from that part of the of the rim to even touch the bead. And then the spacing......?
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  9. Wirespokes

    Wirespokes Beemerholics Anonymous

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    No, I don't see any way they could prevent the bead from coming loose! But they could help prevent the tire from dropping into the well and coming off the rim entirely.
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  10. Plaka

    Plaka Brevis illi vita est

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    They keep the bead from dropping into the center all the way around the rim in the event of a flat.

    It works well---just try to dismount a tire the wrong way!. It's in your manual---You have to start spooning at the divots so the bead can drop into the well on the opposite side of the rim. If you start opposite the divots there is no way to get the tire off. Try it.
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  11. Xcuvator

    Xcuvator Justa Venturer

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    That makes sense, glad you- all cleared that up for me.

    I do wonder though, why don't any of the other wheel manufacturers think it is such a good idea? Maybe there are some others doing it, but I don't recall noticing. Are there?
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  12. mfp4073

    mfp4073 Long timer

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    Good info! Another airhead mystery solved! Thanks all!
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  13. England-Kev

    England-Kev Long timer

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    so if that is correct, then why are they not on the rear wheel as well then?


    I asked BMW why they are there, they said they don't know:D
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  14. bpeckm

    bpeckm Grin!

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    Correct.

    They are on all the BMW wire wheels made for tubes, front and back: as mentioned above, just try to get the tire off without getting the bead down into the center where there are NOT divots while you spoon away on the opposite side.. they ARE effective... !!

    :D
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  15. England-Kev

    England-Kev Long timer

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    Well they ain't on my ST rear wheel :D
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