Bottom Bracket selection help

revmatt
revmatt Posts: 75
edited June 2016 in MTB workshop & tech
Folks I need some advice!

I am building a small Kona Blast for my son. BB shell 73mm.

I have purchased some 165mm FSA GAP gravity cranks with CK- 7550 printed on the inside. Spindle length is longer than my shimano.

They came with a BB which needs replacing: FSA MEGAEXO QUAD

It seems this BB is hard to get hold of. Can somebody point me to a cheap compatible alternative or let e know if I need to provide you with more information.

Many thanks in advance

Regards

Matt

Comments

  • The Rookie
    The Rookie Posts: 27,812
    Its 24mm like Shimano, so I'm guessing there will be a way to use an HT2 BB.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • revmatt
    revmatt Posts: 75
    Ido have an ultegra I can use but needs 3 spacers each side to make it work!
  • supersonic
    supersonic Posts: 82,708
    Have you bought the 83mm crank version?
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  • revmatt
    revmatt Posts: 75
    supersonic wrote:
    Have you bought the 83mm crank version?

    Of what - the BB or crank?

    I have an ultegra roadBB 68-73 that i've put in but have needed to use 3 spacers EACH SIDE to get it to work with the crank. It does work, but obviously there isn't much thread left with which to screw into the frame!

    The frame is 73mm (measured with BB out, edge to edge of where BB would insert.)

    It is the length of crank spindle which is problematic, hence the need for spacers. For some reason the megaexo quad BB is massive and I can't find a replacement.



    Cheers

    Matt
  • dgunthor
    dgunthor Posts: 644
    the shimano MTB hollowtech II bottom brackets work with 2 spacers one side, 1 another (think they are 2mm spacers) - there's more threads on the MTB bottom brackets to allow for this - use one of those? (can normally get one for around £10 online)
  • The Rookie
    The Rookie Posts: 27,812
    That would be for a Shimano crankset, which he's not using......
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • Horton
    Horton Posts: 327
    From what I can tell, the mega exo quad is for 83mm shell width and is mahoosive by the looks of it. I think the gravity gap crankset is meant for 83mm shell so not entirely sure it's going to be compatible

    If you're using 3 spacers per side, that's 7.5mm per side which is basically turning your shell into an 83mm shell then adding a 2.5mm spacer each side to take up the slack left by the fact the old BB was so wide due to the double row of bearings...

    It may well work, but it's probably less than ideal... Depends on how long the threaded section of the BB is and how much is threaded into the shell really.
  • revmatt
    revmatt Posts: 75
    The BB I inherited with the crankset says on the plastic sleeve 68-73 so I'm assuming the whole package has been used on a 73 before.

    I think the problem is the 'QUAD' bearing system, each cartridge has two races of bearings not one thus making the whole deal wider, including the spindle.

    Both the BB and the Cartridges are prohibitively expensive to replace (its almost as cheap to buy a new deore HTII triple crankset).

    My solution so far has been to reduce the number of spacers on the thread to one and use a headset spacer each side on the outside of the BB in between the bearing face and crank face.

    Seems to work...
  • Horton
    Horton Posts: 327
    Good bodge!

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