With the truck strapped and lowered fastest GPS and radar pass was 74.1 mph. Tried a few more times, but the truck kept going airborne....so that is all for now. The 1521 still has ALOT more left in it......its barely breaking 110 temps. All runs were done on 8S. I can go 10S, but it was useless as the truck just hazes the tires hard around 60mph when you roll into the last 1/4 of the throttle.