Changing motor pinion on Panasonic driven bike

[Hermann]

Hi,
would it make sense to change the motor pinion from 9 to 11 teeth on a Panasonic driven bike? I dont usually use the first three gears on my Flyer T8 (with 8 gear Nexus), but I often use the 8th gear and this is often too slow for me on horizontal roads. It would lose some force in a given gear, but I can take a lower gear if I need it. Or am I wrong?

What I dont understand is that supposedly the Flyer does not push over 25km/h (due to the legal restrictions), but how does it measure it? The only information it gets is probably from the motor pinion rpm, but this only makes sense if it would know the gear, and it doesnt seem to be connected to some velocity meter.

The other question is if I would probably lose my homologation if I do this.

Best regards
Hermann

 

[flecc]

It's much better to change the rear sprocket on the Nexus hub gear Hermann,reducing it's size.

There is no mechanical connection between the chainwheel and the motor drive in the Panasonic unit other than the chain, so changing the motor sprocket from 9 to 11 teeth has the effect of raising the cadence (pedalling speed) at which power is delivered, speeding your pedalling by 22%. Since the pedelec torque sensing systen that the unit uses works best at low speeds, that's another reason why this change isn't altogether desirable.

Changing the rear sprocket on the Nexus will make the bike power beyond the legal 25 kph limit and will reduce your range. As you suspected, the road speed is determined by the motor sprocket output speed and the top gear ratio selected by the manufacturer with the Nexus sprocket size.

You may find it helpful to read through the full description of the motor unit and it's workings on my website, and also the working of the software in these units on these two links:

Motor unit and functioning

Software power delivery
.