I have my new third member in and due to the lower gear I'm 10 mph off at 60. I'm pretty sure I remember that I have the yellow driven gear which has 18 teeth. I read somewhere that 1 tooth is good for about a 5 percent change so I ordered a 21 tooth gear for to slow my speedo down by 15 percent. 1/6 is about 16 percent so I should be fairly close I think. Does this sound right?