3x to 1x same hardware – gear ratio change?

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    • #598635

      Just converted a 3×9 to 1×9 and used the middle chainring (32T) as the 1x, took front derailleur off, left the cassette as is. By my simple logic the gears should be the same as when there were 3 chainrings on. Is this accurate? Do the gear ratios change with the removal? If so, please explain. The gears feel different, am I imagining this?


    • #598664

      Not sure I completely understand the question, but I will take a shot.  Gear Ratio and Gear Range are two different things.  For example,  if the small cassette that you removed was a 22t,  and your cassette easiest sprocket is a 34t,  then you are no longer going to feel the ease of spinning a 22x34t Ratio.  This means the wheel only has to spin 0.64 times for every turn of the crank.

      With only the middle chainring and the same cassette, the easiest available is now 32×34. This means for every turn of the crank, the wheel will spin 0.94 times. Unless you are really a strong climber, this will be pretty tough up a hill.

      You can compensate by getting a larger 9 speed cassette.  For example,  you could get a 46 tooth cassette,  meaning a 32×46, which would put the gear ratio back to 0.69 wheel revolutions per crank revolution.  This will feel similar to the easy gear you had before.  The range of gears available will be almost as wide as what you had.  What you won’t be able to restore is the “in-between” gear ratio options that you had with three chainrings and 9 cassette cogs.  The “steps” between the gears will be bigger with a single chainring.

      The trade off people usually make is for the simplicity of no front derailleur and the issue that trying to get a front derailleur to work right has been a challenge since it was invented.

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