http://www.scriptasylum.com/rc_speed/_top_speed.html

Plumb all the things you know into the calculator- motor, voltage, diff ratio etc, then experiment with the spur/pinion ratios until you hit the magic 40mph mark I reckon. Bear in mind the maxx speed you want to run the motor at is 40,000 rpm or there abouts.

Where can I find Brian's calculator?

In the post right above yours. : )

Or, the R/C Calculations link in my sig. Or, the sticky in the brushless section.

Or in my favorites, right under the link to the RCM store!!!!

lol, I don't think he can access your favorites.

Is it just me, or does that sound like a bit of innuendo?.....

gross.