Castle Creations motor and ESC combo recommendations for the Team Associated Semitruck.

Copperhead 10 w/1406-3800kv - stock gearing (20/72) on 2s = ~24MPH
Copperhead 10 w/1410-3800kv - 22T pinion / 72T spur on 2s = ~30MPH
Cobra 10 w/1412-3200kv - 28T pinion / 72T spur on 3s = ~40MPH

Note: All speed estimates are with stock tirediameter, high quality batteries and appropriately sized batteryconnectors.
Always monitor ESC, motor and battery temperatures on newsetups or when changing gearing or batteries.