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  1. #1
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    Bottom Bracket replacement - advice needed

    I am in the process of replacing the Bottom bracket on my 2014 Giant Defy advanced 0. All carbon frame but has a aluminum insert that the bottom bracket fits into. Determined that it is a Press fit Shimano BB86 or that it uses a BB71-41B bottom bracket which I have on order. It uses the plastic receiver that pushes into the BB shell that contains the bearings.

    Popping it out was a breeze with the Park removal tool, and installation looks very simple also.

    The question I have is that the aluminum insert has some very minor corrosion on the outside edge. My thought was to take some very fine emory cloth and brush up the inside of the insert to make it smooth as possible. Then I have heard that if you do have an aluminum insert that you should install grease prior to pushing in the new bearing cups. does this sound correct?

    The reason for the BB replacement is a squeak that happens only when the temperatures get quite warm, and the squeak gets worse the warmer the temperature gets outside. The bearings appear smooth in the old BB but my guess is that as it got warmer the BB shell (flat black Color) got warmer and expanded and allowed a little more space between the aluminum insert and the press fit BB cup which caused the squeak. Hopefully putting a new BB and greasing it well will eliminate the squeak.

  2. #2
    tlg
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    Quote Originally Posted by jackmen View Post
    Determined that it is a Press fit Shimano BB86 or that it uses a BB71-41B bottom bracket which I have on order.
    I would consider one of these instead. Much superior and easier to maintain/remove.
    BB86/92 Thread Together ABEC-3 BB for 24mm (Shimano) Cranks

    The question I have is that the aluminum insert has some very minor corrosion on the outside edge. My thought was to take some very fine emory cloth and brush up the inside of the insert to make it smooth as possible. Then I have heard that if you do have an aluminum insert that you should install grease prior to pushing in the new bearing cups. does this sound correct?
    I would try some CLR and a scotchbrite pad. Should clean up any surface corrosion.
    Yes adding grease is a good idea to keep the alum from corroding more. I use water resistant marine grade grease. It holds up better.


    The reason for the BB replacement is a squeak that happens only when the temperatures get quite warm, and the squeak gets worse the warmer the temperature gets outside. The bearings appear smooth in the old BB but my guess is that as it got warmer the BB shell (flat black Color) got warmer and expanded and allowed a little more space between the aluminum insert and the press fit BB cup which caused the squeak.
    The threaded BB I linked above eliminates this.
    Custom Di2 & Garmin/GoPro mounts 2013 SuperSix EVO Hi-MOD Team * 2004 Klein Aura V

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