How to Upgrade Bottom Bracket to Sealed Bearing (6903 2RS) Hello Viewers! This short video clip is all about upgrading or converting loose bearings found mostly in vintage bike to a SEALED or CARTRIDGE one. The bearings are 6903 2RS which I bought through Shopee. You may see below shpee links to know where I bought bearings and bottom bracket spacers. Shopee Link Sealed Bearing (6903 RS) - Bottom Bracket Spacers -
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