wesnewell wrote:Check the dropouts with a magnet. If they're steel, you likely don't need torque arms. I've built 4 bikes with steel dropouts and no torque arms and none have ever had a problem. Currently running 24s lipo on 1000W rear hub motor up to 4000W and no torque arms. Was running 18s with regen for 8 months prior.
That's definitely playing Russian roulette with dumpster quality bikes like the one in your sig and the one in the original post. Have you measured or even visually checked your dropouts for spreading?
When I first got a hub motor, I thought I could get away without a torque arm too. I was only running 36V/35A, no regen, and I had nice thick chromoly tips on both of the good quality forks I used (one Tange, one Surly).
I never spun an axle, but I spread open the fork tips on both those forks. All I can think is you must be using a motor with a very speedy winding, or else you are ignoring some warning signs. Maybe both.