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I encountered an old and beat up bike today with the bottom bracket pictured below. I could feel play in the bearings but did not see any lock ring or adjustable cup. The 14 mm bolt of each crank arm was tight.

Non-drive side:

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Drive-side:

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Chainring:

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  • Nicely photographed! Can you see any threads inside the hollow where the bolts are? These are needed to engage a crank puller. Try removing the 14mm bolt from one side and see if you see a square taper down the middle. That its bolts and not Nuts suggests some level of modernity.
    – Criggie
    May 31, 2023 at 0:01
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    @Criggie the bike owner was just quickly passing by to know if I could help him fix the slack. After I saw this unknown bottom bracket, I was not too sure how to proceed so he said that it was not a big deal since he was going to get his new bike in two weeks anyway (that bike was really in a rough shape). Looking at the pictures, it indeed seems that there are threads for a crank puller.
    – olliebulle
    May 31, 2023 at 0:15

1 Answer 1

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It's an old American (aka OPC) shell bike that someone put 48 spline BMX cranks and their accompanying BB on.

Some cranks of this pattern are pure enough Profile clones to also use the Profile crank removal tool, and some are not and use their own similar tools. There are improvised ways of doing it but they're not very pro.

The cups can technically receive new bearings in most cases, but the usual approach is a whole new American BB of the correct spindle diameter.

There is no adjustment in these bearings and they usually last a long time because they're enormous. This situation has the DIY look and as such be wary they weren't installed right in the first place, the classic mistake being omitting the tubular spacer inside that these sorts of BBs come with.

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