Please help Gear ratio !!!!

Hi All Experts,

I really need some help on gearing my touring car right. My car is Yokomo MR4TC SP (internal ratio is 2.2)

All my pinion and spur are 64dp

I have set my car to 25t x 108t (spur) , i found there is no top end speed at all.... I tried 27t,19t,15,12t motors

then I tried 33t x 108t, I feel the acceleration is great, but the top end is still lacking.... my friend's 27t motor set-up can beat me on straight ;(

Ok, I bought new set of pinion from HPI 40T(pinion) 90T(spur), going to fit it on my 12x1T reedy ti motor.

I can feel it's gonna be faster , but then I read from web forum... wrong gear may damage motor because Overheated.

Can any expert tell me how to gear a car to go fast without damaging my motor,etc?

Please please help !

Go www.gearchart.com !