Originally Posted by Revo2k

Hey, welcome to the forum.

The percentage is of nitromethane content. Nobody that I know runs 10%. The higher the percent, the more power you'll get, but it'll also shorten engine life (not very noticeably though). I run 30% and so do many others, and some even have ran 40%.

There's always 2 gears, one directly connected to the motor/engine (the pinion or clutch bell) and one that the pinion or clutch bell spins, called the spur gear.

You're right on the gear thing, as long as it's the "pinion" or "clutch bell" (pinion on electric, clutch bell on nitro)(smaller gear of the two). If you went up on teeth on the spur gear (the bigger in size gear of the two), you'd get more low end. If you go down on the spur gear, you get more top end.

Matt