200x sprocket gearing

[kasey200x]

I currently am running a stock sprocket with 22's on the back. And it is perfect for me. I am however switching to 18's and would like the same gearing. So i would have to drop the back sprocket, but how much? Would a 35 tooth be about right?
If there is any mathmatical way at looking at this, can someone give me a name, or what type of math it is. That way i can look it up, and be able to answer the different combinations from now on.
Thanks guys.

[Yamaha_Rules69]

It would be more effective/cost efficient to change the front sprocket first, and see how it does. Standard teeth for the 200x 83-85 is 12 front 40 rear. I know you can go to a 13 front, but a 14 I am not 100%. If you can only go to a 13, you will likely have to change the rear also, probly one tooth less for faster top speed. Hopefully someone that has put 18's on their 200x can give you some tips. Good luck!

[kasey200x]

I currently have the 13 on the front, and when i put the 18's on it i have no top end.. i go through the gears in seconds. Plus, its better on the chain to change the rear sprocket. Making the front bigger puts stress on it. Chain's aren't really a big deal to me. I got a couple, so if I could then i would try to go up another toothe. But it doesn't have that kind of room.

Thanks yamaha, hope someone has tried this. anyone?

[shortline10]

13/34 is what I run

[kasey200x]

Okay sweet. Thanks shortline.

[jb2wheels]

Assuming you can't account for tire growth at speed ...

The 18" tire is 18% smaller around than the 22" tire, so you need gearing approx 18% "taller" or smaller numerically.

The math: difference = (22-18)/22 = .181818181818181 call it .18 or 18%

Stock gearing is 40/12 = 3.33:1

Your target is 3.33 - (3.33x.18) = 2.72:1

Shortline's 34/13 is pretty close = 2.61:1

I'm not sure what sprockets are commonly available, but it looks like you need to change both. Some other options:
34/12 = 2.83
33/12 = 2.75
35/13 = 2.69

[kasey200x]

The only sprocket i see around there (for a decent price) is a 35 tooth. SOO looks like im using the 13/35 combo.
Thanks for that math jb! Makes sense now.