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bottom bracket thread types

paulc33paulc33 Posts: 254
edited May 2011 in Workshop
hi

i want to change my crank on by bianchi to a 170 length and have been looking at getting another fsa crank to replace mine. the only problem is im not sure what tyre of bb i have on mine bike currently or the tread type or size.

Is there any way of finding this information out with out removing my current crank and bb?
2015 Specialized S-Works Tarmac - Ultegra Di2 (7.0kg)
Kinesis Aithein - Ultegra mechanical (7.3kg)
Kinesis Maxlight Xc130 - xt/ xtr (11.3kg)


spin to win!

Posts

  • roadracedaveroadracedave Posts: 107
    Hi,

    The best way to work out which bottom bracket you have got is to measure the width of the bottom bracket shell.

    If you have got an British thread BB then the shell will measure 68mm wide, if you have got an italian one, it will be 70mm wide.

    It's the distance between the two bottom bracket cups, not including the cups.

    I am pretty sure you have will have a british thread bottom bracket and your cranks use the MegaExo bottom bracket.

    Dave
  • paulc33paulc33 Posts: 254
    Yeah I think I have a megaExo grossamer crank. But what I don't get is what other cranks will fit this ?
    Or if I change the crank and bottom bracket what will fit??

    Just after having my bike fit this weekend the shop recommended I look at getting a 170 crank arm.
    2015 Specialized S-Works Tarmac - Ultegra Di2 (7.0kg)
    Kinesis Aithein - Ultegra mechanical (7.3kg)
    Kinesis Maxlight Xc130 - xt/ xtr (11.3kg)


    spin to win!
  • MrChuckMrChuck Posts: 1,663
    If you change the cranks and BB then pretty much anything should fit- as far as width goes your new one will probably come with spacers, and as for thread it' smost likely you've got a British thread as roadracedave says.
  • roadracedaveroadracedave Posts: 107
    The easiest option would be to stick with another FSA chainset, and as long as you buy a 'MegaExo' one, it will be directly compatible with your existing bottom bracket, it would just be a case of unbolting your existing your current chainset, and then sliding in your new one.

    I would recommend changing the bottom bracket at the same time though, as most chainsets come with one.

    I wouldn't narrow your search for a new chainset to a FSA one, purely because you can use the existing BB, as it is really very simple to changet the BB. So unless you particularly like you current chainset and just want to change the length, there would be no harm in looking at any of the other chainsets on the market.
  • paulc33paulc33 Posts: 254
    Thanks for your advise sorry to seem so stupid about it all.
    Final question is it only FDA then that make a megaExo type bottom
    Bracket?
    2015 Specialized S-Works Tarmac - Ultegra Di2 (7.0kg)
    Kinesis Aithein - Ultegra mechanical (7.3kg)
    Kinesis Maxlight Xc130 - xt/ xtr (11.3kg)


    spin to win!
  • roadracedaveroadracedave Posts: 107
    FSA are the only people that make a MegaExo bottom bracket, it is their version of what Shimano call Hollowtech II and what SRAM call Giga-X-Pipe (GXP).

    The above three all look very similar, but are not interchangeable as the interal diameters of the bearings are slightly different.

    You will need to match the bottom bracket to the chainset.
  • Monty DogMonty Dog Posts: 20,614
    FWIW there are 2 sizes of MegaExo - one for aluminium cranks and a slightly narrower one for composite - the two aren't interchangeable. The MegaExo for ally cranks is interchangeable with Shimano Hollowtech II and loads of others.
    SRAM/Truvativ GXP uses a narrow diameter crank spindle on the non-drive side, however you can get an adaptor that allows you to use their cranks with Hollowtech II BBs.
    There is also Campagnolo which comes in 2 flavours - Ultratoque (high-end) and Powertorque which generally aren't compatible with anything else.
    In terms of your BB threads, they are most likely English i.e. 68mm shell, 1.37"x24tpi - Bianchis haven't been made in Italy for a while and aren't even an Italian company - frames are produced in the far east.
    Easiest solution is to buy the matching BB cups for your cranks and save yourself any aggro.
    Make mine an Italian, with Campagnolo on the side..
  • paulc33paulc33 Posts: 254
    Blimey all very confusing think il measure the size of my bottom bracket and then get a new crank and bottom bracket combined.
    I thought my frame would be english thread as I knew frame was made in far east.

    So are there any cranks people recommend? I don't want to spend stupid money on one. Was maybe thinking of a shimano ultegra to match rest of group set but like the look of the FSA cranks at the same time.
    2015 Specialized S-Works Tarmac - Ultegra Di2 (7.0kg)
    Kinesis Aithein - Ultegra mechanical (7.3kg)
    Kinesis Maxlight Xc130 - xt/ xtr (11.3kg)


    spin to win!
  • keef66keef66 Posts: 13,123
    You won't go wrong with an Ultegra chainset and matching HTII BB cups. Not sure what you count as silly money though.
  • Monty DogMonty Dog Posts: 20,614
    If the rest of your drivetrain is Ultegra, then stick with that but if you want a carbon crank, then there's FSA and plenty of others. These days there's little noticeable difference between different models at the same price point - it usually comes down to aesthetics.
    Make mine an Italian, with Campagnolo on the side..
  • paulc33paulc33 Posts: 254
    thanks for all your advise guys final question

    what is the difference between a compact crank and a none compact?
    can i run either on my bike and will it change the way it rides or shifts etc?
    2015 Specialized S-Works Tarmac - Ultegra Di2 (7.0kg)
    Kinesis Aithein - Ultegra mechanical (7.3kg)
    Kinesis Maxlight Xc130 - xt/ xtr (11.3kg)


    spin to win!
  • keef66keef66 Posts: 13,123
    Compact just has slightly smaller chainrings than a standard double
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