Castle Creations motor and ESC combo recommendations for the Arrma Fireteam 6s (1/7th scale).

Mamba Monster 2 w/1515-2200kv - Stock gearing (12/50) on 6s = ~52MPH
Mamba Monster X w/1515-2200kv - 14 pinion/50 spur on 6s = ~62MPH
Mamba Monster X 8s w/1520-1650kv - 16 pinon/50 spur on 8s = ~70MPH

Note: All speed estimates are with stock tire diameter, high quality batteries and appropriately sized battery connectors.
Always monitor ESC, motor and battery temperatures on new setups or when changing gearing or batteries.