New Project....gearing question

[orbitron]

I'm currently beginning a project with my RS4 Rally to turn it into a baja bug. Here's the lowdown. (http://forums.radiocontrolzone.com/showthread.php?t=206114)

Does anyone have any idea what I'll have to do to gear this thing to fit the tires? They are 28cm (11") in circumference, or have a diameter of 9cm (3 1/2").
I am running a P2K copperhead (27T) and am currently using a 30 tooth pinion.
I expect to have to get smaller pinions, is this correct?

[loopy]

ballpark figure=
the tires are 1.5x the size that chassis would have used had you rallied it.

So divide the pinion you have normally used by 1.5
= 30/1.5=20t

go up or down from there :D