My friend Todd Robinson (  wrote an article that appeared in the June 2003 issue of Motorcyclist magazine on gearing.  I found it informative and used it to calculate what sprockets I wanted on my CBR600RR.  Here's the formula and how to use it:


New Rear Sprocket                 Current Front Sprocket
---------------------------       X        -------------------------------        -1, x 100
New Front Sprocket                  Current Rear Sprocket


The result will be the percentage change in gearing.


So for the 600RR, if I wanted to go down 1 in the front and up 2 in the rear,

45      16              720
---   x  ---      =      ------      =    1.1163   -1 = .1163 x  100 = 11.6% Lower Gearing
15      43              645


The result will be 11.6% more acceleration everywhere.  Unfortunately, it will mean an equal increase in RPM's on the freeway at the same speed and your speedo/odo will now be even more off.  There really is no free lunch.


One small benefit if you replace the rear sprocket with an aluminum replacement is that you'll shave about 1 pound off the bike.  That isn't a huge difference, but it all adds up.  Plus that is one less pound of unsprung mass and drivetrain mass.

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