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Thread: BB Orientation

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    BB Orientation

    When installing a BB the the longer taper go on the drive side or the non-drive side?

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    NJS my life! roughrider504's Avatar
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    Drive side, to push the crankarm that holds the chainrings out from the frame. Without this side longer, it could almost rub onto the frame.

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    I assume you are installing a cup-and-cone non-cartridge bb. One way to orient the spindle properly (other than the obvious of measuring and putting the longer end on the drive side) is to install it so the labeling stamped on the spindle would read properly from the riders viewpoint if the bb shell were transparent.

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    Quote Originally Posted by HillRider
    I assume you are installing a cup-and-cone non-cartridge bb. One way to orient the spindle properly (other than the obvious of measuring and putting the longer end on the drive side) is to install it so the labeling stamped on the spindle would read properly from the riders viewpoint if the bb shell were transparent.
    Thanks, that answers one of my questions but I have a factory installed shimano cartridge BB and the longer taper is on the non-drive side. Did they install it backwards?

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    Is the frame English threaded? If so, the bb can only go in one way.

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    cyclist/gearhead/cycli... moxfyre's Avatar
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    Quote Originally Posted by michael word
    Thanks, that answers one of my questions but I have a factory installed shimano cartridge BB and the longer taper is on the non-drive side. Did they install it backwards?
    A Shimano cartridge BB can't be installed backwards on most frames, because the mounting ring that's built-in to the BB cartridge is LEFT-threaded, while the other mounting ring is RIGHT-threaded.

    A cartridge BB should have a label that says which side goes right, and which side goes left. Not all BBs have asymmetrical spindles. For instance, all ISIS BBs have equal length on the right and left sides.

    If it's cup-and-cone, generally you want the longer side on the right to push the chainrings out far enough. But there's no reason why you can't flip it around if you're trying to adjust the chainline, as long as it doesn't cause the chainrings to collide with the chainstay.
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    The spindle offsets also influence the Q-factor, or the distance the pedals are away from the seat tube, as well a chainline.

    However, for a cartridge, there is only one way to install if the threads are cast into the casing... that is, from the right-hand side of the bike. If the cartridge has sealed bearings pressed onto the spindle, and separate threaded retainers for both sides, then it is possible to insert the cartridge either way. In this case, the long side of the spindle would normally go on the chainring side. Note that I am not talking about the new-wave external BB bearings.

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