Wavy bottom bracket washer GXP BSA

lynnsaunders
lynnsaunders Posts: 6
in Workshop
The GXP spindle in a BDS shell is made rigid axially to the frame by capturing the inner race on the NDS bearing. The drive side crank is captured between the spindle end boss and the inner race of the DS bearing and includes a wavy washer. My question is how much you should compress the wavy washer using shims?

Comments

  • paulbnix
    paulbnix Posts: 631
    edited January 2021
    I have gxp bb on both bikes. One is SRAM and the other is Hope with a gxp adapter.

    Neither have any washers on the DS - certainly no wavy washer. I don’t think one is needed because, as you say, the lateral positioning is provided by the NDS bearing clamp.

    Previously I had an FSA MegaExo bb and that used a wavy washer on the DS to preload the bearings.
  • whyamihere
    whyamihere Posts: 7,702
    There's a wave washer for a BB86 press-fit system with GXP, but not for BSA.
  • paulbnix
    paulbnix Posts: 631
    whyamihere said:

    There's a wave washer for a BB86 press-fit system with GXP, but not for BSA.

    Aah ok. Mine are both BSA.
  • lynnsaunders
    lynnsaunders Posts: 6
    Here is a link to Wheels MFG discussion with a diagram that matches the GXP BSA setup I am working on:
    https://wheelsmfg.com/tech/PDF/THREADED-ROAD-SRAM-ABEC3-INSTRUCTIONS.pdf
    The wavy washer is shown as number 8 in the graphic.
    When the spindle is captured on the NDS there is more space on the spindle for the drive side crank than its thickness. So the crank can float on the splines to the point where the small chain comes in contact with the chainstay. This happened to me on my first ride after the build. Spacers are required to center the chain wheels on the chain line of the cassette. In my case I needed 3.8mm of spacers between the bearing cup on the non drive side and the shell to get the proper "stickout" on the drive side to place the middle chain wheel on the chain line defined by the cassette. So my question has to do with how much force you should ask for from the wavy washer to provide the stability required without preloading the drive side bearing too much. In other words should it be 90% collapsed or something less.
  • paulbnix
    paulbnix Posts: 631
    I can see what you mean from that link.

    My 2 Force GXP cranksets have the axle firmly attached to the DS crank so once’s the NDS has been torqued up the DS cannot move so no spacers or wavy washers are needed.

    In your case then it sounds like the DS is not attached to the spindle and you slide it on and torque it up.

    All I can say is that FSA specify 50 nm for the wavy washer in their mega exo bb but that is installed on the NDS.
  • paulbnix
    paulbnix Posts: 631
    Basically I have no control over the position of the chainrings. It relies on the bike, crankset and bb all being compatible.
  • lynnsaunders
    lynnsaunders Posts: 6
    Thanks for everyone's comments. I rode the bike for an hour today and it seems solid and shifts well. What a great hobby cycling is and you get good exercise to boot!

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