I ride like all trails and sand pits, I have 18" tires with 13t sprocket...no problems here[/b]
When I my bike was all stock, I ran 13/39 gearing with stock 20inch tires, and i thought it was perfect for woods and trails. Since I have added the intake and now the exhaust, I feel the 13/39 gearing, is it a bit too low. 13/38 with 18inch tires would be the same as running a 13/42 with 20inch tires. If you were running 13/38 with 18inch tires and then you get a pipe, and intake, you will be hitting the rev limiter imediately. I know that now that i have added the few mods that i have, I am going to go to a 14/39 gearing to compensate. Also with all the low gearing, the front end defiinately tends lift very very easy!
Joe