hmm, yeah. i never did put my 1515 1.5D on 6s or my 1512 1.5D on 5s. the 1515 1.5D on 5s does near 70mph in my truggy geared 15t/48t. it is insane. at 50mph it will wheely. my 1512 on 4s was fast too but not as fast. prob in the 60mph range. you probably were too aggressive. but i would be worried about the motor more than the esc. the 1515 1.5d on 6s is at about 62k rpm and the max on Neu is supposed to be 60k. i know there are guys that push the limit but i try to keep mine at 55k rpm or less. try the 1.5d on 5s. you wont be disappointed.