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Is it ok to use a 68mm external (hollowtech II) BB in a 73mm shell?
Thanks
yep, but use 2 spacers on the driveside and one on the non-driveside
Yep, but ignore the advice above and use one spacer.
Which side for the spacer?
drive side 1 spacer
Excuse my ignorance but if I don't ask I'll never know. How does a 68mm fit in a 73mm shell, it'll be too small?
Yup, getonyourbike has it the wrong way round.
AndrewJ - MemberExcuse my ignorance but if I don't ask I'll never know. How does a 68mm fit in a 73mm shell, it'll be too small?
External BBs don't really have a width- they're 2 seperate bearing cups. The cranks are 73mm, so you use the BBs plus spacers to bring the BB shell up to size.
Doh! Me being simple... 😳 Don't know why I said that when I just rebuilt my hardtial and bouncer the other week. 68 and 73mm BBs respectively.
Where's the hammer to the head smiley when you need one? 😆 🙄
Surely the crank must actually be 75.5mm if you still have to run one spacer in a 73mm BB?
That sounds like it might actually be right. In my defence it does not matter at all 😉
Where as running 3 spacers in a 73mm BB might have. 😳 😆Northwind - Member
That sounds like it might actually be right. In my defence it does not matter at all
External BBs don't really have a width- they're 2 seperate bearing cups. The cranks are 73mm, so you use the BBs plus spacers to bring the BB shell up to size.
Thanks for that 🙂
What about the plastic tube, that will be 5mm shorter, do you still use the tube?
yup, still use the tube because of the spacers, the BB cups are still sitting the same distance away from each other so the tube will still work. Making sense?
If you put a 68 BB into a 73 wide shell with a spacer isnt the tube going to be a little further away from the cups? A small detail I guess but curious.
It's not a 68mm BB- what you have, is either a 68 shell with 3 spacers, or a 73 shell with 1. The 2 extra spacers that you use with your 68mm shell make it the same width for either option.
Just to add to the confusion. The road bike cups are sold as just 68mm with no spacers and have a shorter tube in the middle. But you don't need the tube anyway
Perfect, thanks all.
To add to this, I use 83mm cups in a 73mm BB shell. Shimano M815 Saint cups.
Plenty of extra thread to support the BB mounted chain device on the drive side.