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  1. #1
    mtbr member
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    Sep 2010
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    635

    Euro cups/bmx crank conversion - help needed

    I have a 'custom' 24" bmx cruiser. It's been modified into a 'b6er' (26" rear/27.5" front).
    For a long time I ran a standard square taper bb and mtn cranks. Recently I got a set of
    S&M euro cups and installed my old Redline Flight bmx cranks. Because Redlines bb spindle is proprietary, I had to work with the spacing. As you can see from the picture,
    the clearance on the left crank is pretty minimal. The spider is drilled out to 74mm bcd so I could use a 28t front ring.

    The problem I'm having is that the euro cups seem to be getting gritty MUCH faster
    than a standard mtn bike bb would wear out. I'm not sure what has made them wear out so quickly. When I installed everything I made sure there was no excessive friction so I know the cups were not damaged initially.
    Attached Thumbnails Attached Thumbnails Euro cups/bmx crank conversion - help needed-b6-bmx-chainsuck-tab.jpg  

    Euro cups/bmx crank conversion - help needed-b6-bmx-drilled-redline-bmx-cranks.jpg  

    Euro cups/bmx crank conversion - help needed-b6-bmx-left-crank-clearance.jpg  

    Euro cups/bmx crank conversion - help needed-b6-bmx-side-shot.jpg  


  2. #2
    Nouveau Retrogrouch SuperModerator
    Reputation: shiggy's Avatar
    Join Date
    Dec 1998
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    48,315
    Quote Originally Posted by phoenixbikes View Post
    I have a 'custom' 24" bmx cruiser. It's been modified into a 'b6er' (26" rear/27.5" front).
    For a long time I ran a standard square taper bb and mtn cranks. Recently I got a set of
    S&M euro cups and installed my old Redline Flight bmx cranks. Because Redlines bb spindle is proprietary, I had to work with the spacing. As you can see from the picture,
    the clearance on the left crank is pretty minimal. The spider is drilled out to 74mm bcd so I could use a 28t front ring.

    The problem I'm having is that the euro cups seem to be getting gritty MUCH faster
    than a standard mtn bike bb would wear out. I'm not sure what has made them wear out so quickly. When I installed everything I made sure there was no excessive friction so I know the cups were not damaged initially.
    Bearings will wear out quickly if you have too much side (pre)load. Very easy to over do it with BMX cranksets.
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