I was going by the info traxxas provided. If it is the stock brushed esc, then 25c is the max. I bet your not using the stock esc, XL5? And how would you feel if the car caught on fire using something quicker? This is for bashing, not racing ovals, the hardest thing on equipment. The motor will last a lot longer on 25c. If they wanted to go faster I would recommend 3s.