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How does chain ring size reduction affect motor performance?

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How does chain ring size reduction affect motor performance?

Old 09-05-23, 09:55 AM
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How does chain ring size reduction affect motor performance?

Recently, I replaced the 44T chain ring with a 38T chain ring on my Shimano e8000 assisted trike. I was going to ride in the Adirondacks for a week and figured that would give me a lower gear range. After I got back, I was playing with a couple of apps which are supposed to help customize the performance. On one of the apps, called eTuning, I saw a screen where I could tell the app about my drive train. The default selection for the front chain ring was 44T, but I wasn't able to change it without buying a "license" for $0.99. I'm not prepared to invest that kind of money without knowing what results I'm likely to get. So, if anyone knows what advantage is to be found by telling the motor what size chain ring is attached to it, could you please let me know?

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Old 09-05-23, 11:16 AM
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Electric motors have optimum speeds for maximizing efficiency, usually the faster the better up to an extent, so probably the smaller chainring increased your efficiency (especially ascending). Accordingly, less power was lost to heat providing less wear. I'm using a 30 tooth chain on my BBS02- equipped full suspension bike since I ride exclusively off road on steep trails. It's possible the motor simulator @ ebikesca can provide some info.
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Old 09-06-23, 06:37 AM
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This is the ultimate ebike motor simulator. No fees.

Motor Simulator - Tools (ebikes.ca)

Provides more information than most people can mentally process. They actually measured the systems they have listed. Can even predict when the motor might overheat.

What I found impressive is how much effect gearing has on whether the motor ever hits full rated power. Also how motor efficiency varies with how it is spinning, the watt gauge on this display doesn't tell one much about how much power the motor is actually putting out.
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