ZP-A84-T2 CRANK 曲柄 A84-170mm (Alloy Forged 6061-T6) CHAIN RING 链轮 (iron) SPIDER 爪 24T*38T(steel) CHAINLINE 链线 50mm COMPATIBIL ITY 变速兼容 3*9S/10S B.B.T 中轴 Chrome molybdenum steel