Well I have finally gotten the Trackstar 4.5T 550 installed along with a Brushlesshobbies.com LT4 esc. I'm running the stock spur with a 14T pinion and it's ballistic! I absolutely LOVE this combo!!! The motor is crazy fast and after a full pack it's temping at 130. Anyone looking for a killer setup should give this a try. I'm using a Zippy 5900mah 60C pack and I'm getting 16-17 minutes of HARD running out of it. That's in my yard driving through grass too. I'm sure on a track I could get around 19 minutes or so out of the pack.