Changing the gearing ratio on a mid-drive.


New Member
Hi all.

I just started comminuting to work every day on a rebranded Shengyi 250W mid-drive ebike. This is my first ebike and I love it, however I feel like the gear ratio is too low.

The bike has 7 internal gears (hub gear) and about 80% of my commute I spend on 6th or 7th gear. When cruising in 7th I normally bike approx. 21mph. The problem is I simply can’t keep up with the motor in 7th gear, and I end up spinning the pedals without any resistance, so the motor cuts off.

The current setup is a 18T rear cog and a 38T chainring. Ideally, I want to replace the chainring with a bigger tooth count, but Shengyi use these special chainrings I can’t seem to find anything matching online (see picture). The rear is a standard shimano. I was planning to change the rear to a 14T to get the gearing ratio I want, but I’m afraid 14T is going to have to few teeth engaged to the chain, and the mid-drive is going to rip it apart after a few weeks.

I’m very new to ebiking and would just like to know if any of this makes sense? Are there any other way to make my commute more enjoyable? And does anyone know anything about the chainring?




Well-Known Member
Nevada City, CA & Paradise Valley, AZ
Specialized's highest torque 250W mid-drive ebikes come equipped with 11-42t cassettes. I often ride the flats in the 11t cog with max power. No issues so far after ~1,000 miles. Others with many more miles have not reported issues with this gearing on this blog. Based on this I think you're OK with 14t.

Ride on...😎