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Thread: Valve Stem Placement?

  1. #1
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    Valve Stem Placement?

    This is another of those "why didn't I notice this earlier?" type of questions, but ...

    my bike as the valve stem on the right side of the front wheel, but on the left side of the rear wheel. Why did BMW do that?
    Royce
    On the coast of Kansas
    2012 F800ST

  2. #2
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    Quote Originally Posted by royce View Post
    This is another of those "why didn't I notice this earlier?" type of questions, but ...

    my bike as the valve stem on the right side of the front wheel, but on the left side of the rear wheel. Why did BMW do that?
    To properly balance the bike at high speed.

  3. #3
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    Sometimes it is accessibility. On some bikes the rear valve stem is deliberately located on the opposite side of the final drive (chain or belt).
    If you don't have dual front rotors, the stem is on the non-rotor side. If same the wheel is used on different bikes, the critical application determines the location and on all other bikes it may not make sense.

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    Quote Originally Posted by billy walker View Post
    To properly balance the bike at high speed.
    Billy, is that your supposition, or has BMW said this somewhere? Your answer makes sense for, say, the S1000RR or some other "high speed" ride, but the F800? Seems improbable to me.
    Royce
    On the coast of Kansas
    2012 F800ST

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    Quote Originally Posted by EMSimon View Post
    Sometimes it is accessibility.
    I understand this logic. But on the F800ST, the rear valve stem is located under the hot muffler and seems it would be "better" on the other side.
    Royce
    On the coast of Kansas
    2012 F800ST

  6. #6
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    Quote Originally Posted by EMSimon View Post
    Sometimes it is accessibility. On some bikes the rear valve stem is deliberately located on the opposite side of the final drive (chain or belt).
    If you don't have dual front rotors, the stem is on the non-rotor side. If same the wheel is used on different bikes, the critical application determines the location and on all other bikes it may not make sense.
    Actually if we leave Harley out of the equation most bikes run valve stems in the middle of the rim. Even 90 degree stems are located in the middle of the rim the vast majority of the time. and the exit direction doesn't seem to follow any sort of logic.

  7. #7
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    Quote Originally Posted by royce View Post
    I understand this logic. But on the F800ST, the rear valve stem is located under the hot muffler and seems it would be "better" on the other side.
    Trust me. Logic plays no part on valve stem location although it certainly should.

  8. #8
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    Quote Originally Posted by royce View Post
    This is another of those "why didn't I notice this earlier?" type of questions, but ...

    my bike as the valve stem on the right side of the front wheel, but on the left side of the rear wheel. Why did BMW do that?
    Put your own type of prefer d valve stem in and then the winning will stop.

  9. #9
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    To properly balance the bike at high speed..
    and if the rear wheel is balanced it would be moot.

  10. #10
    Benchwrenching PGlaves's Avatar
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    You need to see the valve stems the OP is talking about to appreciate what they are. They are all steel stems that screw into threads in the wheel, sealed with an O ring. They stick out horizontally from one of the spokes cast in the wheel. The disks are not in the way and you are not reaching in to try to check the air or add air to a stem located in the middle of the rim. The stems are horizontal on the sides of the wheel, near but not on the rim.

    I personally consider this stem placement the design innovation of the decade. Yes they are on opposite sides of the motorcycle but very simple to use nonetheless.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

  11. #11
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    a little OT, but I bought some aftermarket stainless valves for my 1150--beemerboneyard. I weighed them and they tipped the scales at 26.9 grams each. That is some heft.

  12. #12
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    Quote Originally Posted by PGlaves View Post
    You need to see the valve stems the OP is talking about to appreciate what they are. They are all steel stems that screw into threads in the wheel, sealed with an O ring. They stick out horizontally from one of the spokes cast in the wheel. The disks are not in the way and you are not reaching in to try to check the air or add air to a stem located in the middle of the rim. The stems are horizontal on the sides of the wheel, near but not on the rim.

    I personally consider this stem placement the design innovation of the decade. Yes they are on opposite sides of the motorcycle but very simple to use nonetheless.
    Paul, you are exactly correct, and I was not complaining about anything, simply asking is anyone knew the logic behind BMW engineers placing the stems on opposite sides of the wheels. (I have an analytical mind and such thoughts often bother me) After thinking about it a while, and riding to Salem and back and checking tire pressure several times, I agree with you about it being a design innovation and I say kudos to the BMW engineers.

    Thx for your reply. Royce
    Royce
    On the coast of Kansas
    2012 F800ST

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