SUMART | NEWS & HOW-TO How to Install a BCD 104 Chainring with SUMART CBT-2 and FLEXI 9 A practical guide to a clean, secure chainring installation using two compact SUMART tools. SUMART 104 BCD, 36T chainring mounted on the crankset.   What is BCD 104? BCD stands for Bolt Circle Diameter. A 104...