齒比(大盤50-39T);飛輪(12-25T)

沒試算算齒比～
____大盤______________________________________
飛輪---||-----(12)...(13)...(14)...(15)...(17)...(19)...(21)...(23)...(25)
____(39)：3.25_3.00_2.79_2.60_2.29_2.05_1.86_1.70_1.56
____(50)：4.17_3.85_3.57_3.33_2.94_2.63_2.38_2.17_2.00
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