XT8 - selecting the right system

[jnev]

This speed calculator made by BrianG was designed to help with this exact question.
http://www.scriptasylum.com/rc_speed/_top_speed.html
Just plug in the values for the XT8, and play around with the gearing for the speed you want. I would also recommend 4s for racing, and the 5s for bashing.5s on pretty much all tracks will be way too fast/powerful on a 2200KV motor. With 4s, you can gear up or down depending on the track. 6s is just ridiculous on a 2200KV motor, but it can be done, so if you can handle it, go for it!