Originally Posted by bds81175

You're not doing it wrong. The Pro4 4600 is a 540 size motor (shorter length) while the HD series are 550. I believe the 540 4 pole or 550 2 pole are the only legal motors for ROAR events. I've used 4000kV Tekin Pro4's and 4300kV Tekin Pro4 HD's and I would have to agree with BMain....the HD's are overkill in most hands on most tracks. From what I have seen, in this class most people are going to go faster by going slower. I'm actually considering going to a 550 2 pole to smooth out the power delivery.