ZP-A81-A1 CRANK 曲柄 A81-170mm (Alloy Forged 6061-T6) CHAIN RING 链轮 32T(steel) SPIDER 爪 BCD 104/94mm CHAINLINE 链线 50.5mm COMPATIBIL ITY 变速兼容 1*11S B.B.T 中轴 Chrome molybdenum steel