>>1817463>>1817478See:
https://www.sheldonbrown.com/cribsheet-unthreaded-bottombrackets.htmlAs for which bearings you'll need, 6003DU is the appropriate code if you have a spindle with the most common 17mm diameter.
>>1817374 You probably have a cassette spacer missing or out of place. See:
https://dassets.shimano.com/content/dam/global/cg1SHICCycling/final/ev/ev/EV-CS-M7100-4598B.pdf>>1817460Rollers require you to balance, that's their defining feature. They've largely fallen out of favor now that smart trainers that make indoor training more effective and engaging are common.
