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Shimano LP-20 Square BB Drive Side Plastic Cup

Posted: 24 Oct 2020, 11:42am
by Brian73
I've just stripped a 1994 MTB with an FC-MC30 STX chainset and discovered an LP20 BB with the plastic cup on the drive side.

Never seen one like this before, the plastic cups are generally found on the non-drive side, unless it's an FAG with them on both sides.

Can I replace it with a standard flanged metal drive side BB or does the FC-MC30 STX chainset require this LP20 type?

https://si.shimano.com/pdfs/ev/EV-BB-LP ... -1243B.pdf

It appears to be an odd convention, any idea why Shimano did this?

Re: Shimano LP-20 Square BB Drive Side Plastic Cup

Posted: 24 Oct 2020, 1:38pm
by gregoryoftours
You can replace it with any BB of suitable drive side spindle length. It's a mystery to me why these bbs were made the 'wrong' way around.