Strategy for removing a bottom bracket with plastic retainers? Bottom brackets that have plastic retainers have a reputation for being problematic to remove. Often the tool interface on the plastic retaining ring will shear off if the plastic is old or the bottom bracket is stuck (How can I remove the stripped plastic cups of a bottom bracket?).  I (everyone?) would like to avoid such a situation if possible.

What steps can one take to improve ones chances of sucessfully removing the plastic retaining rings?

Some ideas:

The plastic rings are typically made from Polyamide, which is resistant to attack by hydrocarbon lubricants.  A penetrating oil might work (to the extent that they work anyway).

The plastic rings are made from a thermoplastic so heating is probably a bad idea.  Having said that, it should be possible to heat up the bottom bracket shell with a heat gun or similar to around 100 Celcius.  This would expand the bottom bracket shell by some fraction and make it easier to remove the retaining ring.  Unfortunately the coefficient of thermal expansion of the rings is likely higher than that of steel.  Maybe freeze the rings instead?

Maybe it's possible to attach a metal fastener (by pinning perhaps?) to the retaining rings.  I expect this is in the realm of fantasy.

EDIT:  To clarify, I am asking exclusively about threaded bottom brackets.
Based on my experience with such cups I suggest a rather robust approach:


cut off the external parts of the plastic cups with a hot knife
chisel away material from one side to expose the outer edge of the cartridge
apply penetrating oil to all areas
heat the bottom bracket with a heat gun (bear in mind the heat may damage the frame's paint @Argenti Apparatus)
drive out the bottom bracket by whacking the bottom bracket spindle with a mallet


if that doesn't work
* remove the bearings and the spindle
* uncover the other side of the bottom bracket
* drive out the cartridge with an improvised punch (eg steel tube, hex socket) and a press, apply penetrating oil and heat as before

I'm confident I should be able to remove such a bottom bracket in less than two hours now, if I must. I also shall not ever put myself in a situation where this may happen.