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The precision the app provides was enough to determine that there was a 7Hz variance on two points of the wheel rotation, 180 degrees apart. I was able to solve that by removing the rear sprocket and rotating it two bolt holes clockwise and reattaching.


Well, that's interesting.  I still have some vibration coming from the back wheel on my SR/S that I can't seem to find the source of.  I might try this and see if rotating the sprocket reduces that vibration.

Is the motor alignment adjustable?  My belt rides up tight against the inside edge of the pulley at the motor when it's otherwise perfect at the rear wheel, and that always bugged me.  I think I looked for the motor mounts briefly, but didn't really see any way to adjust that.

> Is this a Day-1 issue?

Yes.

> You probably don’t have to many miles on it yet?

Right, maybe 500 miles.

> Seems odd, for the buzz to be RPM related, on an Electric Bike.
> If you hear it, when on your Center Stand, my guess is its Belt or Rear Wheel/Brakes related.

Well, that makes a lot of sense...

> The 22, that I saw, at a dealer, had a super tight belt (almost no deflection).
> Not sure if 22’s are shipping that way now.

Mine was that way as well.  I've been playing around a lot to get it "right" (a little more relaxed, centered perfectly on the rear sprocket).

> Maybey play with Belt Alignment (and/or Tension).

Right, I tried that, both looser and tighter.

> Also, if you apply the rear brake does it make any difference?

No, but see below...

> FYI - I’ve had all plastics off my 21 and that power-point doesn't reflect how much fun it is, putting the Tank Plastics back on.
> Things fit very tight and there are a lot of cables to stuff back in, under the “tank”.

Right, that main piece took a lot of work to get back on.

> Sure something could be loose under there, but I find an RPM related resonance to be odd.

I think you're right.

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I followed the video above, got all of the plastic off, got the "trunk" off, and the noise was coming from below all of that, likely either inside of one of the two chargers, or between the chargers and the battery (again at 850 RPMs).  It looked like a huge task to keep going (to disconnect all the wiring and remove the chargers) so I gave up at that point.

So now that I read what you said above, I think that's exactly it.  When I spin the rear wheel with the bike on the stand, the rear brake drags just a little bit for about 1/10th of the rotation.  I just chalked that up to the brake pads being brand new and maybe not sitting quite right, thinking it'll go away with time.  But it makes perfect sense that this would cause a vibration through the rest of the bike, and resonate at one particular frequency, 850 RPM in this case.

Soooo, what do I do about this?  Is there an adjustment I can make to loosen the rear brake so it doesn't drag?  Is this a defective, warped rotor that needs to be replaced?

Thanks for your response, and any other suggestions!

Got it.  I'll give that a try first and let you know.  Thanks!

I don't have my SR/S yet ('won't until next week), but I've been playing around with the iPhone App in preparation.  When I look at the default "Sport" ride-mode in the app, it seems to imply that it'll only use 80% of the power, and that you'd need to create a "Custom" ride mode to use all 100%.  Could that be the case here?