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Advice on changing a bottom bracket

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  • June 6, 2018 at 8:13 am #28592
    Shades

    Thought I’d expand my bike maintenance CV to bottom brackets.  My Genesis Equilibrium 20 has a threaded, pretty sure it’s 105 (brit thread I assume), BB.  Looks like a ‘piece of cake’ to change looking at videos and books.  Probably change it for an Ultegra BB and invest in a BB tool; Park version looks good.  What could possibly go wrong?  Is it essential to torque the BB cups?  I have a small torque wrench but not a large one (which are quite expensive).  Any risk of crossed threads? Particular grease to use?  Should the crank shaft come out easily (with a bit of mallet assistance)?

    I just don’t want the ‘walk of shame’ into the LBS!!

    Some of the other bikes don’t have Shimano, but that’s another project.

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  • June 6, 2018 at 10:17 am #920927
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    Anonymous

    Don’t forget that the cups

    Don’t forget that the cups have different threads – left-hand cup has a right-hand thread and the right-hand cup has a left hand thread. So as you face the bike (from either side), it’s clockwise to loosen and anti-clockwise to tighten.

    No need to torque it, just pretty tight as mentioned above. Give the shell a really good clean out and grease, hand install the cups as far as possible and if in doubt, back out the cups and reinsert to make sure you don’t cross-thread.

    June 6, 2018 at 9:16 am #920925
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    StraelGuy

    This is a very easy job but

    This is a very easy job but bear in mind the Ultegra bottom brackets are smaller than standard Hollowtech 2 bottom brackets and will need the new Park Tool BBT-59.2 rather than a standard Hollowtech 2 tool.

     

    When fitting the new one, the correct torque value is approx. 30 ft/lbs but mechanics have been hand tightening them for years though so just use common sense. Make sure you can screw it in a few turns by hand before you use tools, this will reduce the chance of cross-threading.

     

    Lube-wise, I always use copper grease for bottom brackets but any good grease would. Be liberal with grease and grease both the threads on the bottom bracket cups and the threads in the frame. Water tends to accumulate inside the bottom bracket area so you can never have too much grease.

     

    The crank itself should be easy enough to remove. If it’s a bit stuck just wallop the end with either a plastic hammer or a lump of wood, there’s nothing holding it in once the left crank is off so it shouldn’t give you any grief.

     

    When you’re re-installing the left crank, as you install the plastic preload keep pausing and swinging the crank arm. As soon as you start to feel a smidge of resistance, stop and tighten the two bolts on the crank arm.

     

    Have fun!

    June 6, 2018 at 9:12 am #920923
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    henryb

    Certainly there’s a risk of

    Certainly there’s a risk of crossed threads but a low risk on the Equilibrium 20 because it’s a steel frame – messing up the threads is harder to do with steel. Likewise, probably no need to tighten the cups to a specific torque – with a steel frame you can get away with tightening them to “quite tight”. I’ve changed a Shimano Hollowtech BB and it’s not that hard.

    HB

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