I have now geared my 1515 2.5d Tekno Neu up. 56/25 is a bit much for this combo on 4s but temps after 5min where great. ESC 107*, motor 121*, Lipos 105*, with an ambient Temp of about 87*. However performance was poor and top speed actually seemed to suffer. I changed the gearing to 62/25 which gives me a bit more top end than the 54/20 and still has plenty of low end. This is giving me about 35MPH which is plenty to have fun with till I upgrade to 6s. Overall - Very happy with this motor, glad I didn't fall victim to another Feigao.