What is the spindle diameter on the FSA Gossamer TT MegaExo crankset? 24 mm or 30 mm? I can't find a direct answer anywhere. I have seen MegaExo described as 19 or 24 mm, but "Gossamer" as 30. I'm looking at the aforementioned crankset for my Giant Trinity BB90 bottom bracket shell, but I don't want to go 30 mm.

1 Answer 1


I believe Gossamer is more of a ‘level’ of FSA products rather than a particular crank model.

MegaExo is an FSS external bearing bottom bracket type for BSA threaded shells. It uses a 24mm spindle diameter.

According to this article 24mm spindle external bearing road cranks are compatible with BB90.

  • Maybe contact FSA and ask what they have that is compatible with BB90? Commented Jan 28, 2018 at 14:36
  • 1
    I believe the diameter of MegaExo spindle is 24.05mm, which is why a grease and rubber mallet is required if you insert a MegaExo crank into a Shimano bottom bracket, which is a true 24.00mm.
    – Rider_X
    Commented May 28, 2018 at 17:03
  • 1
    @Rider_X personally have a SLK MegaExo in a Shimano external bearing BB and it is indeed a bit tight. Commented May 28, 2018 at 17:10

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