Many bikes have rubber seals on the wheel bearings. There’s also a tortuous path through the seal. They are not completely sealed, no rotating part can be, there’s always got to be some wiping going on. But it’s as good as it’s going to get.
I’m not sure why we don’t see some kind of gasket or boot on the seat post and maybe stem too, it would be cheap insurance given how often seats especially get stuck.
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Genesis 49:16-17