changing the gearing
 

Im looking for a bit more top end out of my madrat and i understand you can do this by changing the gear for less teeth. (correct me if im wrong).

I dont want to loose to much acceleration, so what would be the best number gear to go for ?

Depend on your motor.
If you whant to change the gearing for more speed, change the motor pinion for more teeth.
I use 24T on motor pinion with the 80T spur, with my 8.5T motor.

You will loose a bit on acceleration, but gain on top speed.

I use a 23 tooth and a 6.5.

its a standard motor and ESC so far, going to run it till the ground before i upgrade.

Where you all buying them from? any links ?

With the 8.5T ezrun motor, with less power than the robitronic I now use, I used a 28T motor pinion.
With a standard motor, you can try this too...

I buy my stuff in france (I'm a french) but if you're english, try fusion hobbies, or maybe Jespare, forum sponsor.