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I have a second hand frame circa 2014 that measures about 74mm across at BB.

I'm fitting an Ultegra crankset.

Shimano states I need a BB94-41 for a shell width of 86mm ?????

Am I reading this wrong? how can a BB86 fit in a frame width of 74mm.

Im confused

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  • I don't know the specific numbers, but most BB setups are "adjustable" to some degree, since the cup on at least one side can be screwed in (or not) by a variable amount. I would guess the adjustability amounts to 5-10mm total. Mar 7, 2018 at 18:19
  • its a press fit BB
    – roger44
    Mar 7, 2018 at 18:20
  • A photo of the BB shell will help here. Which Ultegra version crank do you have and where did you find the information on what BB you need? Mar 7, 2018 at 19:29
  • its an FC 6800 CRANK
    – roger44
    Mar 7, 2018 at 19:35
  • I looked up which bb I needed from shimano produce data specs.
    – roger44
    Mar 7, 2018 at 19:36

2 Answers 2

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You have the 73mm version of either BB30 or PF30. Running a Shimano road crank will be physically impossible because the spindle isn't long enough.

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The spec sheet you provided a link to says the recommended BB for a FC-6800 crank is a Shimano SM-BB72-41B. I believe that BB is a BB86 type for a 86.5mm wide press fit shell (see here).

If you have a press fit frame that measures 74mm at the shell I think that would be a BB30 or PF30 which both have 68 and 73mm versions.

I think what you will need is a BB30/PF30 to BB86 adapter. I haven't googled to see it such a thing exists but it seems possible because BB86 has a 24mm spindle whereas BB30 has 30mm.

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