What upgrade gave you the biggest e-bike performance boost?

[Overclockedrider]

I'm thinking of giving my e-bike motor a boost and would love to hear what worked for you. Which motor or controller upgrade made the biggest difference in how your bike performed? Any advice or stories you can share would be awesome

 

[Circuitrid3r]

Switching to a sine wave controller made my ride way smoother, and I can climb hills much better now. I also got a Bafang 750W mid-drive, and it's like night and day for hill climbing, but the battery still lasts