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Missing part for bottom bracket

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Missing part for bottom bracket

Old 05-16-21, 02:58 PM
  #1  
Daniel4
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Missing part for bottom bracket

It looks like my wife's bike is missing the part of the bottom bracket that caps and protects all the dust and dirt from getting in. Probably the last bike mechanic didn't re-assemble it properly.

Can anybody name all the missing parts? I'm guessing there will be a cap and some sort of ring lock nut. Are these parts universally sized that I can buy online and assemble on my own or should I take it to another bike mechanic?

Thanks
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Old 05-16-21, 03:08 PM
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If it's a standard shimano bb with a fully assembled spindle and bearings that is inserted through the drive side, and then a kind of retainer on the non drive side, meaning that there are only 2 parts, then there is nothing else.
https://si.shimano.com/#/en/EV/BB-UN55
If it's from some other manufacturer, then maybe there could be a separate dust cover but I don't have experience with other types of designs.
the shimano bb has seals near where the spindle protrudes from the end of the main assembly. You would be able to see them if you take off the crank arms. But I don't think it's necessary. You could also stick your face close to the gap with a lamp to take a look for the seal.
one thing though is that the gap between the crank and the bb shell looks really wide. Is the q factor symmetric? You can measure from the outer face of each crank arm at the pedal spindle to the seat tube to see if the distance is the same on both sides. I had an experience once a long time ago where a shop replaced my 68mm bb with a 73mm bb so the non drive side crank arm was really far out. That was when I decided to do everything myself.

If both sides are equal, then you can measure the chainline to see if it's correct. If the chainline is further out than desired, you could switch to a shorter bb spindle to reduce the gap and q factor.

Last edited by tomtomtom123; 05-16-21 at 03:39 PM.
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Old 05-16-21, 04:04 PM
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It's a cartridge type BB.
That's the way it is.
Pic is for removal tool attachment, but you can see what it is minus the NDS (plastic) "cup/retainer

"
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Old 05-16-21, 06:30 PM
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Thanks for being willing to toss the mechanic under the bus when you didn't know what was the norm.

As has been said the image is the usual assembly. I see no missing parts. Andy
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Old 05-16-21, 06:30 PM
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If you are asking about the opening at the spindle end of the crank arm (the visible female threads at the extreme left edge of your photo) you need a crank arm dust cap. These vary a bit in diameter and threading among crank manufacturers but the Shimano type is most common and any bike shop should have them at low to no cost. They are available in metal or plastic and are installed and removed with a large screwdriver slot, a hex key hole or two small holes for a pin spanner depending on make.
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Old 05-16-21, 07:13 PM
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Originally Posted by HillRider View Post
If you are asking about the opening at the spindle end of the crank arm (the visible female threads at the extreme left edge of your photo) you need a crank arm dust cap. These vary a bit in diameter and threading among crank manufacturers but the Shimano type is most common and any bike shop should have them at low to no cost. They are available in metal or plastic and are installed and removed with a large screwdriver slot, a hex key hole or two small holes for a pin spanner depending on make.
If this is what the OP was talking about I ow an apology. If not then my comments stand. I will add that there are millions of bike that are ridden for many thousands of miles without crank arm extractor thread dust caps and not suffer any harm or issues. Andy
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Old 05-16-21, 07:26 PM
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Originally Posted by HillRider View Post
If you are asking about the opening at the spindle end of the crank arm (the visible female threads at the extreme left edge of your photo) you need a crank arm dust cap. These vary a bit in diameter and threading among crank manufacturers but the Shimano type is most common and any bike shop should have them at low to no cost. They are available in metal or plastic and are installed and removed with a large screwdriver slot, a hex key hole or two small holes for a pin spanner depending on make.
The OP provided a quality photo...centered on the axle/bb cup. Don't you think if he was talking about the dust cap he might have actually centered the photo on that particular part? Overthink much?
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Old 05-17-21, 08:44 PM
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Originally Posted by Daniel4 View Post
Can anybody name all the missing parts? I'm guessing there will be a cap and some sort of ring lock nut. Are these parts universally sized that I can buy online and assemble on my own or should I take it to another bike mechanic?

Thanks
Sometimes you tighten the non-drive-side lockring all you can and there's still an unsightly gap that fills with dirt. A plastic spacer from an old cassette will fit in there.
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Old 05-20-21, 06:50 PM
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Thank you to all who have responded.
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Old 05-20-21, 07:05 PM
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apply some black plastic paint to the off colored part & it'll likely be forgotten about. Might even add some watts!
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