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Discussion Starter · #1 ·
Going to lube my chain last night and I noticed the crank was really hard to spin. Long story short, found that the BB shell is about 89.5mm but the BB cups, pressed into the plastic tube thing, are about 90.5mm (numbers made up) apart. Upon reinstalling cups into shell, I found that I could slide the whole assembly back and forth. It's been like this since I got it but I've never had a BB30 before so I didn't know that little gap was abnormal. What am I doing wrong here?
 

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Going to lube my chain last night and I noticed the crank was really hard to spin. Long story short, found that the BB shell is about 89.5mm but the BB cups, pressed into the plastic tube thing, are about 90.5mm (numbers made up) apart. Upon reinstalling cups into shell, I found that I could slide the whole assembly back and forth. It's been like this since I got it but I've never had a BB30 before so I didn't know that little gap was abnormal. What am I doing wrong here?
What crankset/BB are you using?

BTW the Whippet is BB92, not BB30.
 

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Discussion Starter · #3 ·
Ahh yes, brain fart. Crank is a Shimano SLX and BB is Shimano SM-BB91-41. I'm not knowledgeable enough to know if that's a compatible BB or not. My custom builds often get messed up for this exact reason...
 

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Ahh yes, brain fart. Crank is a Shimano SLX and BB is Shimano SM-BB91-41. I'm not knowledgeable enough to know if that's a compatible BB or not. My custom builds often get messed up for this exact reason...
Is the crank loose in the BB or the BB loose in the frame?
 

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Discussion Starter · #5 ·
BB loose in the frame.

The crank seems to bottom out at the right point via the fixing bolt. Then I can just slide the whole thing back and forth in the shell.
 

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BB loose in the frame.

The crank seems to bottom out at the right point via the fixing bolt. Then I can just slide the whole thing back and forth in the shell.
Did you use a press (like a headset press) to install the BB?
 

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Is the 2.5mm driveside spacer still attached?

If that goes walkabout the bb won't fit the shell properly.

Also, IIRC the BB for Shimano press fit mtbs is the SM-BB71. The 91 is a road bike part, which is a different size to mtb parts (natch).

Speaking of which, press fit BBs are easily the worst piece of tech to hit the maintstream in the last five years...
 

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Is the 2.5mm driveside spacer still attached?

If that goes walkabout the bb won't fit the shell properly.

Also, IIRC the BB for Shimano press fit mtbs is the SM-BB71. The 91 is a road bike part, which is a different size to mtb parts (natch).

Speaking of which, press fit BBs are easily the worst piece of tech to hit the maintstream in the last five years...
I see SMBB91-41A for mtb
SMBB91-41B for road

I have yet to install one so do not know if there is a spacer included.
 

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Discussion Starter · #9 ·
Did you use a press (like a headset press) to install the BB?
I didn't install it originally. My mechanic/brother did. But after my my bearing failure and discovery of the problem, I was able to remove the cups by gently gripping them with vise-grips and wiggling them out. To re-install them, I just pressed them in easily by hand. The non-drive side was actually spinning in the shell until the grease worked in and the bearing broke free. Basically there's no tension on the cups. If the bearings were to seize up on a ride the cups would probably start spinning in the shell. Anyway, this season is over for me and I'm replacing replacing it. I just hope to get the correct part and install it correctly next time around.
 
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