In three years of use, I have had to change the cogs twice because the 11 tooth wore away. I changed the chain only recently.Quite right Mike Killay , Prince of Denmark at 36v, it's when you start pushing the power output above 750 w that problems with drivetrain kick in. I love everything Ive heard so far about this new wee Bafang unit.
Now I know that an 11 tooth cog is prone to heavy wear, but if it was a lot thicker, it would last longer. It was designed for pedallers not ebikers.
Even the pedallers complain of premature wear.
The root of the problem is the need for a wide range of gears, which is why I suggest that for an ebike, 4 thicker cogs and a heavy chain would likely do better.