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What is the washer for on my BB?(9 posts)

What is the washer for on my BB?wilsonc
Jan 5, 2004 10:38 AM
On my Shimano BB-UN72 italian bottom bracket that I'm about to install, I dont know what this washer on the right hand side is for (red arrows in the pictures). It is removable. When the BB is threaded all the way into the shell, the washer is visible. Do i leave it in, or remove it? what is it for?

Looks like a 1mm spacer...Mike Prince
Jan 5, 2004 11:08 AM
I would install the BB without it and if everything works OK (shifts well, chain not noisy) then your chainline is likely OK and you don't need it.

Interesting that a new BB has a spacer with it. Usually a spacer is used if the chainline is off, but I've not seen many BB's from the factory with one included.

Guess Shimano has finally gotten the messageOldEdScott
Jan 5, 2004 11:15 AM
that their BB spec if off by 1 mm, causing untold misery nationwide in the form of chainring rub.
Install without it...Mike Prince
Jan 6, 2004 7:08 AM
And if everything is OK then forget about it.
not a new BBwilsonc
Jan 5, 2004 2:37 PM
this is not a new BB... its just one I got from my brother to replace the Dura Ace 7400 BB with non-sealed bearings that was getting kinda crunchy.

doesn't look like a spacer to meDougSloan
Jan 5, 2004 3:14 PM
From the looks of the photo, the washer is a lot smaller than the outer plate of the cup, small enough that it would not keep the cup from being threaded in further nor meeting up sufficiently with the bike's bb housing. Looks like it would actually go inside the bb housing. So, I give it a big "huh?".

exactly what I thoughtwilsonc
Jan 5, 2004 5:22 PM
Thats exactly what I thought. Like you said, i gave it a big "huh?"
doesn't look like a spacer to meM_Currie
Jan 5, 2004 10:38 PM
If the washer is slid over the threads, then no matter how small or poorly configured for contact with the face of the BB shell, it would have to prevent the cup from being screwed in further, wouldn't it?
Jan 6, 2004 7:33 AM
That's possible, but it's a pretty goofy way of doing it. Seems like the mating of surfaces would be much more solid if it were a ring that matched the profile of the outer surface.