Havent tried different gearing yet, I would like to try 20-39 just to see what happens. Factory is usually really close on gearing though, I dont know what 10 tooth drivers are going to do either. I did change secondary spring and helix, went lighter spring and a dual stage helix. Made about 8 sled lengths faster according to lining up with my old 2001 Zr 500. Impoved midrange and top end a lot.