I prefer the 9 speed 12-36 as it has the best separation ratios.
12, 14, 16, 18, 21, 24, 28, 32, 36.
It works the best with a half step setup. I like 48x45
If you have 48, 45, 42, 39 chain rings it is an uncomplicated way to change for flat to hilly terrain
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Cambodia bikes, Bridgestone SRAM 2 speed, 2012 Fuji Stratos...